r’”~ 87 aq aquaculture with treated wastewater · sandra johnson cointreau — ... julio c....
TRANSCRIPT
351.1
87 AQ
APPLIED RESEARCHAND TECHNOLOGY(WUDAT)—TECHNICAL NOTE NO. 3INTEGRATED RESOURCERECOVERYPROJECT
~, r’”~~..Lr ~ E (‘En- ‘L( ANfl
S~L~:I~ i.-~ (~.
Aquaculture WithTreated Wastewater:
A STATUS REPORT ON STUDIESCONDUCTED IN LIMA, PERU
CompiledandEditedbySandraJohnsonCointreau
— —
— —
THE WORLD BANK—WATER SUPPLY AND URBAN DEVELOPMENTDEPARTMENT
A JointUnited NationsDevelopmentProgrammeandWorldBankContributionto theInternationalDrinking WaterSupplyand SanitationDecade
UNITED NATIONS I~1 9%
351.1—4910
INTEGRATED RESOURCE RECOVERY REPORT SERIESGLO/ 84 / 007
A series of reports are being prepared by the Resource RecoveryProject as part of a global effort to realize the goal of the United NationsInternational Drinking Water Supply and Sanitation Decade, which is to extenddomestic and community water supply and sanitation services throughout thedeveloping world during 1981 to 1990. The project objective is to improveurban waste management and encourage resource recovery as a means ofoffsetting some of the costs of community sanitation.
Volumes published to date include:
No. 1 Recycling from Municipal Refuse: A State—of—the—Art Reviewand Annotated Eibliography (World Bank Technical Paper No. 30)by S. Cointreau et al.
No. 2 Remanufacturing: The Experience of the United States andImplications for Developing Countries (World Bank TechnicalPaper No. 31) by R.T. Lund.
No. 3 Aguaculture: A Component of Low Cost Sanitation Technology(World Bank Technical Paper No. 36) by P. Edwards.
No. 4 Municipal Waste Processing in Europe: A Status Report onSelected Materials and Energy Recovery Projects (World BankTechnical Paper No. 37) by J.G. Abert.
No. 5 Ariaerobic Digestion: Principles and Practices for BiogasSystems (World Bank Technical Paper No. 49) by C.C. Gunnersonand D.C Stuckey et al.
No. 6 Wastewater Irrigation in Developing Countries: Health Effectsand Technical Solutions (World Bank Technical Paper No. 51) byH. Shuval et al.
Forthcoming:
No. 7 Co—Composting of Domestic Solid and Human Wastes by L. Obengand F. Wright.
No. 8 Wastewater Management for Coastal Cities: Ocean DisposalTechnologies by C. G. Cunnerson et al.
In addition to the above, an informal Technical Note Series is alsobeing initiated with the publication of this document. The purpose of thisnew series is to provide wid~er and quicker distributiori of the interim resuitsof ongoing projects, and to initiate an exchange of views on the subjectmatter.
APPLIED RESEARCHAND TECHNOLOGY(WUDAT)—TECHNICAL NOTE NO. 3INTEGRATEDRESOURCERECOVERYPROJECT
Aquaculture WithTreated Wastewater:
A STATUS REPORT ON STUDIESCONDUCTED IN LIMA, PERU
Compiled and Edited bySandraJohnsonCointreau
contributors
Cari Bartone,Julio MoscosoHugo NavaCueto,NormaNoeMocetti
assistedby
BalfourHepher,Netty Buras,MariaLusiadeEsparzaCarmenVargasde Mayo, ElenaGil Merino, RaulPorturas
ManualTantaleanVidaurre,SonjaCalleEspinozaMariaTeresaAmayaArroyo, Tula Luna, MercedesCarrasco
L~RARY,INT~:r~.~L\ l~
CE ;TR~ ( ~ ~J’~LY[1 1
HT~ueTe! (:7L; - L ~/~/142
f’1: ~ / (~(c~(0LO: .~s.i.
THE WORLD BANK—WATER SUPPLYAND URBAN DEVELOPMENT DEPARTMENTA JointUnited NationsDevelopmentProgrammeandWorldBankContributionto the
InternationalDrinking WaterSupplyandSanitationDecadeUNITED NATIONS 9~I 9%
Copyright © 1987The International Bank for Reconstructionand Development/The World Bank1818 H Street NWWashington, D.C. 20433, USA
All rights reservedManufactured in the United States of America
This is a document published informally by the World Bank, as a jointcontribution with the United Nations Development Programme to theInternational Drinking Water Supply and Sanitation Decade. This note wasoriginally prepared as an internal discussion document. The findings,interpretations, and conclusions are those of the authors and should not beattributed to the United Nations Development Programme or the World Bank, totheir affiliated organizations, or to any individual acting on their behalf.
— 111 —
ABSTRACT
Fish culture is one means of producing a large amount of proteinmaterial in a relatively small amount of space. This study has shown thatsignificant quantities of protein for either human consumption or livestockfeed could be produced from wastewater—based aquaculture, which could beintegrated with sewage stabilization lagoon systems. Reuse of treated sewageto fertilize the microbial food chain for aquaculture presents one of the mosteconomic resource recovery options for cities in developing countries.Wastewater—based fish and prawn culture research, development, and demonstra—tion efforts were conducted in Lima, Peru, through the sponsorship of theÏJNDP/World Bank Integrated Resource Recovery Project and the CTZ, the agencythrough which the Federal Republic of Cermany provides technical assistance todeveloping countries.
Fish and prawns were cultured in wastewater stabilization lagoonsoperating as polishing lagoons in series with primary and secondary ponds.Some of the fish ponds were operated as batch—type (receiving make—up wateronly) rather than flow—through ponds. The fish fed on the natural food chainfertilized by the nutrients in the treated wastewater; no supplemental feedwas added.
The hypothesis being tested was that fish and praw-ns would grow inwastewater—based ponds and be acceptable for human consumption either directlyor indirectly (for example, fish may be used as a protein source for livestockor a second generation of fish ponds). It was found that the environmentalconditions in the ponds were satisfactory for the survival and growth oftilapia and carps, particularly in the cycle—end polishing ponds. Althoughthe prawns grew satisfactorily, they did not survive unanticipated largefluctuations in water quality due to shock loadings, which may be common underuncontrolled conditions. The experience in Lima (and at other sites discussedin the literature) indicates that ammonia is a key water quality constraintfor fish growth and production, and that total ammonia should not exceed 2.0mg—N/l.
Raw fish examined in this study had no parasites on the gilis orskin, or in the muscle. Furthermore, the bacteria bad of the muscle portionof raw fish was acceptable for human consumption. However, higher bacterialevels within the digestive tract and peritoneal fluid could lead to conta—mination of food preparation areas during fish cleaning. Experiments inprocessing the fish through salting and smoking showed promise as a means ofminimizing public health risks to consumers. Indirect consumption throughcrushing the fish and disbursing them to other fish ponds or for use as live—stock feed has not been tested.
A demonstration project, where missing parameters will be verified,that is expected to verify aquaculture yield results and elaborate on thehealth and economic aspects of this study will soon follow.
PREFACE
More and more peopbe in developing and industrial countries alike arerecognizing the need for technical and economic efficiency in the allocationand utilization of resources. Resource recovery and recyling provide develop—ing countries with a means of optimizing the use of indigenous naturalresources, reducing the need for imports and thus conserving foreign exchange,increasing local employment opportunities, and developing industrializationskills.
In 1981, a global research, development, and demonstration project onintegrated resource recovery (GLO/84/007, formerly CLO/801004) was undertakenby the World Bank as executing agericy for the Unjted Nations DevelopmentProgramme (Divisiori of Clobal and Interregional Projects). The goals of theproject are to achieve economic and environmental benefits through sustainableand replicable resource recovery and recyling of liquid and solid wastes frommunicipal and commercial sources.
A major goal of the project is to develop and encourage resourcerecovery as a means of offsetting some of the costs of community sanitation,which may account for more than 50% of total expenditures. Aquacubture inhigher—level wastewater treatment (polishing) bagoons offers one method ofpartially or totally offsetting these costs. This would not only make itpossible to achieve high quabity standards for effluent discharge for environ—mental improvement but would also enhance the opportunities for effbuentreuse. This note documents research, devebopment, and demonstration studieson fish and prawn culture conducted at the San Juan Lagoons in Lima, Peru.Potential public health risks of fish consumption were examined through micro—biological analyses of both raw and processed fish. Financial support wasprovided by the United Nations Development Programme, Clobal and InterregionalProjects Division. Additional financial support came from the Cerman Agencyfor Technical Cooperation (CTZ).
An international group of experts as well as a group of Peruvianscientists have participated in the research, advising, monitoririg, oranalysis. Most of their names appear on the title page of this document,however, the list does not inciude many others who took part in the project.We are grateful to them all.
Your comments on this note would be welcome, and we would be gratefulto receive any case study information from which future editions of theresource recovery series could benefit. Please send your comments to AppliedResearch and Technology Unit, Water Supply and Urban Devebopment Department,World Bank, 1818 H Street, N.W., Washington, D.C. 20433, USA.
S. Arlosoroff
Chief (WUDAT) andUNDP Projects Manager (WUD)
The World Bank
— vii —
CONTRIBIJTORS
This note was compiled and edjted by Sandra Johnson Cointreau, aconsultant to the World Bank, who was responsible for coordinating thestudies in Lima. The text is bargely gleaned from the reports of the Limaresearchers:
CarI Bartone, Maria Lusia de Esparza, and Carmen Vargas deMayo, Centro Panamericano de Ingenieria Sanitaria y Cienciasdel Axnbiente (CEPIS), who provided water quality monitoring andsanitary engineering technical assistance to secure retativelysteady—state conditions within the ponds for aquaculture;
Julio C. Moscoso, Hugo Nava Cueto, Elena Cii Merino, andRaul Porturas, Universidad Nacional Agraria (UNA), who studiedfish culture and fish processing, as well as the microbiologyof processed fish;
Norma Noe Moccetti, Manuel Tantalean Vidaurre, Sonja CalleEspinoza, and Maria Teresa Amaya Arroyo, Universidad NacionalMayor de San Marcos, Centro de Investigacion Instituto Vete—rinario de Investigaciones Tropicales y de Altura (USM/IVITA),who examined bacteria and parasites in raw fish and prawns, aswell as parasites in pond sediment; and
Tula Luna and Mercedes Carrasco, Instituto de Investi—gacion Tecnobogica Industrial y de Normas Tecnicas (ITINTEC),who investigated mesophilic batch digestion of animal manureand collaboration with UNA for special fish culture of tilapiain concrete tanks.
To assist the local research scientists, the IJNDP/World BankIntegrated Resource Recovery Project arranged for expert consubtants BalfourHepher and Netty Buras to provide regularly scheduled technical assistance onfish culture and epidemiology, respectively.
Alejandro Vinces, Luis C. Carrillo Macedo, and Javier R.Seminario, Program de Proteccion Ambiental y Ecologia Urbana,Ministerio de Vivienda y Construccion, coordinated the dailyactivities of the various research groups participating in theproject. They were also responsible for operating andmaintaining the San Juan lagoons in accordance with waterquabity information obtained and technical assistance providedby CEPIS.
- viii —
S. Arlosoroff, Project Manager, and Charles G. Cunnerson,then Senior Project Officer, of the UNDP/World Bank GlobalProject on Integrated Resource Recovery (GLO/80/004) conceivedand directed the overall Lima waste—fed aquaculture program.Mr. Klaus Kresse, Chief of Special Studies, Water Supply andSanitation of the Cerman Technical Cooperation Agency (GTZ),participated in directing the second phase of the studies.
Eric Perrin, Resident Representative of the IJNDP in Lima,helped to obtain the initial government approval for researchand thereafter assisted with the administration of researchcontracts.
In March 1985, the GTZ sponsored an Expert Panel Meeting of special—ists to examine Phases 1 and II of the Lima fish culture studies and recommenda plan for a possible Phase III: Balfour Hepher (Israel, fish culture usingwastewater), Netty Buras (United States, epidemiology of waste—fed fishculture), Roger Pullin (the Philippines, fish genetics and fish culture),Peter Edwards (Thailand, fish culture using human wastes), Dhrubajyoti Ghosh(India, traditional fish culture using wastewater), and Hans Schlotfeldt(Cermany, epidemiology of fisheries).
— ix —
~ONTENTS
Page No.
List of Tables ix
List of Figures . ........ .......x
1 . BAC~CROLJNDOM WASTE—BASED AQUACULTURE. . . . . . . . . . . . 1
2. THE CITY OF LIMA .3
Setting 3
History of Developments 4
3. THEWASTEWATERSTABILIZATIONSYSTEMSINLIMA ..... ..8
Structure . . . . . . . . . .......... .8
Study Methods and Measurements 8
Pond Management . 8SelectionofSpecies 11S tocking 12Fiows 13EnvironmentalObservations 13Water Quality Measurements 13SedimentQualityMeasurements 14Primary Productivity Measurements 17Aquaculture Evaluation Techniques 17Harvesting 17Food Processing 18Bacteria Measurements 18Parasite Measurements 19Fish Toxicology Measurements 19
4. FINDINGS •.. •......... .21
Hydraulic and Loadings .•.... 21
Physical—Chemical Water Quality 21
Microbiological Water Quality 28
(Continued)
—x—
Page No.
S ediment Quality . . .29
Aquaculture Resuits. . . . . . . . . . •....... . . . . . . . . •... .39
Fish Microbiological Assessment... . . . . . . . . 45
Toxicological Assessment . . . .47
5 • ~ONCLUSIONS . . • • • • . . . . . • . . . . • • • . . . . . . . . . . . . .49
6 • RECONMENDATIONS.. . . . . . . . . . . • . . . . . . . . . 5 1
REFER.ENCES . . . . . . . . . . .54
— xi —
LIST OF TABLES
Page No.
Table 1. Components of the Experimental Programand Analytical Techniques . . •.••.•.. . . . 15
Table 2. Preservation of Samples and Sample Holding...... .......16
Table3. HydraulicandørganicLoadsonPonds. •.•.• .......22
Table 4. Envirorunental Conditions in Aquaculture Ponds:Averages of Daily Samples • . . . • • . . •... • . • .24
Table 5. Range and Averages for Physical and ChemicalParameters of Aquaculture Ponds Recorded in Phase 1 ..25
Table 6. Range and Averages for Physical and ChemicalParameters of Aquaculture Ponds Recorded in Phase II.......26
Table 7. Environmental Conditions in Ponds: Averageof Weekly Samples . . . . • . . • . . . . . . • 27
Table 8. Frequency of Positive Identification of EntericProtozoa and Helminths 31
Table 9. Frequency of Positive Ideritification of SalmonellaSerotype • . . . . , . . . . 37
Table 10. Summary of Measurements and Calculated Parametersper Controls and Final in the Monoculture ofTilapia in Phase I........ .........•.................40
Table 11. Summary of Growth Data in Prawn Assays, Phase 1
Table 12. Summary of Measurements and Calculated Parametersper Controls and Final in the Monoculture ofTilapia, Phase II........ 43
Table 13. Summary of Measurements and Calculated Parametersper Controls in the Polyculture of Carps andTilapiainC—lLagoon,Phasell ..44
Table 14. Resuits of Analyses on Fish Muscie Sample ...48
— xiii —
LIST OF FICURES
Map of the San Juan Efftuent Reuse ProjectShowing Cultivated Household Plots 5
Map of the San Juan Lagoons Showing Levels ofTreatment Prior to the Aquaculture Studies . 9
Pond Arrangement During Aquaculture Studies.. .....10
Concentration Indicator Bacteria in Effluents,Series 1 ......... . . .30
Concentration of Indicator Bacteria in Effluents,Series 2.................... 30
Total Coliforms in Pond Efftuents and Sediments,Series l............................. 32
Total Coliforms in Pond Effluents and Sediments,Series 2. . 33
Fecal Coliforms in Pond Effluents and Sediments,Series 1 34
Fecal Coliforms in Pond Effluents and Sediments,Series 2
Salmonella sp. Concentration in Pond Effluentsand Sediments. .. . 36
SPCinPondEffluentsandSediments . 38
Page No.
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
—1—
Chapter 1
BACKGROUND OM WASTE-BASED AQUACULTURE
Fish culture is one means of producirtg a large amount of proteinmaterial in a relatively small amount of space. Economic benefits from fishculture are usually higher than those from traditional agricultural crops.Fine—grained organic matter added to fish ponds provides a suspended attach—ment surface and food supply for bacteria and protozoa. These microorganismsalso take up nutrients from the water. After they build up their protein—richceil mass, they serve as food for fish. Other organisms, such as phyto—plankton and zooplankton, benefit from the growth of bacteria and protozoa,and in turn serve as fish food (9, Hepher).
One of the richest, yet cheapest, sources of organic matter is humanexcreta. Whether fish ponds receive human excreta directly or through sewageinfluent, traditional systems and special demonstration facilities indicatehigh fish yields. In India, for example, production rates from fish pondsutilizing wastewater have ranged from 3 to 9 tonnes/ha/year (9, Hepher).
Poor people in the cities of developing countries have traditionallyfound ways to conserve resources and recycle wastes as one means of carvingOut their livelihood. For example, poor urban dwellers on the fringe ofCalcutta have been using sewage to enhance fish culture sirice the turn of thecentury. The ratio of sewage to water there is about 5:1 (15). There arepresently about 4.5 thousand hectares of sewage—based fish ponds surroundingCalcutta —— stocked mainiy with carp and tilapia, which supply an annualharvest of about 6,000 tonnes (18).
Direct use of night soil to fertilize fish ponds has been more fullypracticed in China than anywhere else. In fact, in 1966, 90 percent of theexcreta generated in the country was applied to agricultural lands and fishponds. In Taiwan there are several thousand hectares of fish ponds receivirigexcreta. A significant portion of the fish ponds in Indonesia have over—hanging latrines that directly discharge excreta into the underlying waters(15).
The polyculture of carp, tilapia, and mullet fish in wastewatertreatment ponds has been practiced in Israeli kibbutzim. Fish are oftenallowed to rest in clean water for several weeks to help depurate them beforeconsumption. Because of the concern over public health risks, Israel nowallows only polishing ponds or freshwater ponds receiving secondary—Leveltreatment effluents to be used for fish culture (15). Studies in Israel haveshown that adding wastewater to fish ponds can markedly increase fish feedutilization and fish yield —— which rose as much as 75 percent in one set ofexperiments (22).
In Cermany, several hundred hectares of fish ponds (mostly stockedwith carp) receive sewage that has been partly Created in sedimentation tanks
—2—
and then diluted with relatively fresh water (15). Fish yields from thewastewater—fed ponds are reportedly much higher than those from regular pondsin the region (22).
Despite the efforts that have already gone into promoting waste—basedaquaculture, much more remains to be done, as indicated recently by a panel ofinternationally recognized experts who were asked to examine the global stateof knowledge on waste—based aquaculture. They pointed Out that
while there has been extensive experience in Asia (mainly inChina, Indonesia, Vietnam and others) on use of human excretain fish ponds and, to a much less widespread extent, on fishculture in sewage in India, most of the experience has beendevoid of data generation and scientific examination. Datagenerated have largely been from traditional systems withoutflexibility to experimentally adjust and examine variables,replicate studies, and thereby obtain reasonable confidence inthe resuits.
Significant studies have been done primarily in Israel,Thailand, and now Peru to examine individual growth rates, pondyields, and public health consequences of sewage—based fishculture under various comparable experimental configurations.In Thailand, comparable studies have been done to examineexcreta—fed fish culture systems. These studies are essentialto the eventual formulation of design standards and monitoringcriteria for waste reuse (21).
—3—
Chapter 2
THE CITY OF LIMA
SETTINC
Lima, the capital of Peru, is located on the Pacific Coast of SouthAmerica. It has a moderate climate, but receives little rai although thereis often a mist in the morning. Cloud cover prevails during most of thewinter months (July through September).
Aside from three small river basins that cut through Lima (Rio Rimac,Rio Lurin, and Rio Chillon), the city rests on desert land. Croundwater isdeep and fairly well contained by overlying sandy soils interspersed withlayers of impermeable day soils. The regional groundwater flow is from theAndes Mountains westerly to the Pacific Ocean.
The city has a popuiation of about 5 million, of which roughly 50percent are recent rural immigrants living in precarious housing with limitedaccess roads. About 65 percent of the houses have access to water suppiy andsewerage or other sanitation infrastructure (8, 16). And about 60 percent ofthe city’s refuse is collected (10).
Epidemiological data indicate that the most common infectiousdiseases, in order of prevalence, are acute diarrhea (primarily rotovirus,enterotoxigenic and enteropathogenic Escherichia coli, and Campylobacter),typhoid and paratyphoid fever, intestinal parasite afflictions (primarilyascariasis and giardiasis), and viral hepatitis (8, 35). Acute diarrhealdiseases among infants represent the leading cause of child mortality in Peru,and the typhoid and paratyphoid fever rate there is the highest in LatinAmerica (6).
The above—mentioned diseases are believed to be transmitted prin—cipally through the consumption of food and water that has been contaminatedby excreta (17). These diseases account for nearly 50 percent of the totalnumber of illness cases in Lima (35). Contamination occurs through numerouschannels, most notably via raw vegetables that have been irrigated withuntreated wastewater, inadequate sanitation, pigs raised at clandestine refusedumps, and flies that have been in contact with exposed refuse heaps (10).
It is estimated that some 80 percent of the wastewater from cities indeveloping countries is being used raw or partially treated for irrigation(33). With Lima’s high rate of population growth and the lack of rainfall inthe region, the city’s underlying groundwater supply has droppedconsiderably. Thus potable water is precious and reuse is the norm. Sincemuch of the reuse is uncontrolled and includes numerous taps on the city’s rawsewerage system (10), measures to provide wastewater treatment prior to reusecould go a long way toward reducing public health risks from excreta—relatedinfectious diseases.
—4—
HISTORY OF DEVELOPMENTS
The concept of fuil—scale reuse of treated wastewater has beensteadily developing in Lima for more than two decades —— beginning in 1959with a presentation of how to treat Lima’s wastewater in stabilization lagoonsby Alejandro Vinces, formerly President of the Parks Service (SERPAR), to theNational Congress of Sanitary Engineering.
Beginning in 1961, SERPAR supervised the development of 21stabilization lagoons in San Juan de Miraflores, a municipality in thesouthern zone of Lima’s metropolitan area (6). Supreme Decree No. 105—67—DCSof 1967 authorized SERPAR to create forestiand by irrigation with treatedeffluent from the San Juan lagoons (36).
More than 500 ha of land (most of which was desert, and part of whichwas closed sanitary landfill) are presently being irrigated with effluentsfrom the San Juan lagoons —— of which about 1,280 ha consist of woodiand and220 agricultural land, with another 1,300 ha being planned for greenbelts withlow irrigation requirements (6). Pilot plots of various fruits (e.g., pine—appies and papaya), vegetables (e.g., corn and platanos), and flowers (e.g.,roses and hibiscus) have been created on—site (10, 36). Part of the irrigatedland is farmed by 16 families who have set up irrigation systems to use thepartially treated wastewater to grow cow fodder and vegetables (6). Figure 1shows the location of plots cultivated by these families, as well as largerplots cultivated by agricultural cooperatives.
The movement toward wastewater reuse has been paralleled by a growingconcern about air pollution and the need to preserve greenbelts of forestlandto filter and oxygenate the air (36). Air pollution, coupled with cool dampclimatic conditions during many months of the year, lowers human resistance torespiratory infections. A review of Peru Ministry of Health statistics showsthat tuberculosis and other respiratory infections are among the 10 leadingcauses of morbidity in Lima and constitute about 20 percent of the totalnumber of cases of disease reported there (35). As a step toward improvingenvironmental quality, Legislative Decree No. 143 of 1981 created the Programof Environmental Protection and tJrban Ecology to authorize the cultivation andpreservation of greenbelts (36).
Research and development studies have been an integral part ofSERPAR’s efforts to promote wastewater reuse. With local fundjng as well asexternal support from the International Development Research Center —— Canada(IDRC) and the Panamerican Health Organization (PAHO), CEPIS has studied themechanisms of treatment occurring in the lagoons and the levels of waterquality achievable through various sequences of lagoons and periods ofretention (6, 37, 38, 39).
A special multisectoral commission formed in Lima in 1973 has beeninvestigating the possibility of using a 5,000—ha site (called San Bartolo)south of Lima for the fuil—scale demonstration of wastewater reuse (figure1). In 1980, a mission from Israel established the prefeasibility ofirrigation with treated wastewater at San Bartolo. In 1981, SERPAR engaged
—5—
4 4
“4 4 4
4 4
4 4
4 ~
1 4 D 01 *4 40 ~ 4 4+ ~g2 4• ~ —, •~ 4 4 4 4 4
4 4 4 4 4 4 4 4 4 4
S ~ 4 ~ 4 4 4 4~S.
4 4 4 ~ 4 ~ 4 4 4
N 4 4 4 4 4 4 4 4
•1
u
00
—6—
the National Agrarian IJniversity (UNA) to further evaluate costs and benefitsof the San Bartolo project (10). The concept was also studied from anengineering perspective by contractors to the Lima Water Supply and SewerageAgency (SEDAPAL) as part of a master plan for water supply and sewerage forLima (17).
In 1983, the Inter—American Development Bank (1DB) and SEDAPALapproved and allocated funds for an in—depth study of costs and benefits andfor the development of preliminary engineering designs. A group ofconsultants carried Out this study in late 1984 and early 1985, and theyrecommended the reuse of 2.5 m3/s of treated effluents to irrigate some 5,000hectares (34).
1f a reuse system is to be successful in the long term, it must limitthe accumulation of salts and metals in the soil column, especially in adesert climate such as Lima’s. To accomplish this, wastewater treatmentshould be capable of removing a high percentage of suspended solids and ofprecipitating dissolved solids. Also, longer retention times are recommendedto enhance the die—off or removal of potentially pathogenic micro—organisms,and thereby minimize public health risks (1, 39). Aquaculture could beincluded in the final stages of treatment with a view to generating revenuesfrom the sale of the fish or plant byproducts that could offset the costs ofobtaining a higher quality wastewater effluent (9, Hepher).
In a modest experiment conducted during the mid—l970s, an attempt wasmade to grow tilapia fish within secondary wastewater treatment ponds at SanJuan (6). However, the water quality was found to be unsuitable to supportfish growth (10).
Beginning in 1983, external support from the World Bank, IJNDP, andCTZ made it possible to incorporate tilapia fish and giant prawn culturestudies into the overall scheme and operation of the lagoons —— with lagoonsbeing resequenced to obtain higher levels of treatment. After initialharvests showed good growth and survival of fish, several varieties of commoncarp were added to examine the effects of polyculture.
These aquaculture studies were performed by local research teams atUNA, CEPIS, and the University of San Marcos Institute of VeterinaryInvestigations (USM—IVITA) under the umbrella of SERPAR initially, and thenunder the Program of Environmental Protection and Urban Ecology (6, 27, 28).As part of the aquaculture studies, bacteria and parasites were monitored inlagoon effluents and sludges, as well as in raw and processed fish.
In cooperation and in parallel with these studies, but with financialsupport from local industries, the Institute of Technical Investigations andStandards Setting for Industry (ITINTEC) has studied mesophilic anaerobicdigestion of animal manure and provided some of the slurry to UNA for use inaquaculture of tilapia in tanks supplied with potable groundwater (24).
—7—
Furthermore, a study sponsored by the U.S. Agency for InternationalDevelopment (USAID) was conducted in 1984—85 to evaluate the cost—effective—ness and public health risk of growing duckweed (Lemnaceae) as a poultry feed(10). Floating macrophyte populations have the potential to improve effluentwater quality from the ponds since they are capable of stripping nutrients andheavy metals from wastewaters (6).
—8—
Chapter 3
THE WASTEWATERSTABILIZATION SYSTEMS IN LIMA
STRUCTURE
The wastewater treatment facility in San Juan de Miraflores basoperated continuously since 1964. The facility consists of 21 wastestabiljzation ponds occupying 20 ha. The ponds are divided into twobatteries: the upper battery consists of ten ponds, and the lower batteryeleven ponds. Final effluents from each of the two batteries are used for theirrigation of farmiand and forestland (6).
Wastewater in the upper battery receives primary and secondarytreatment. Up until the start—up of aquaculture studies, the ponds in thelower battery were operated at the primary and secondary treatment level. SeeFigure 2 for a layout of the lagoons prior to the aquaculture studies (37).
The wastewater inftuent at the San Juan facility is residentialsewage from about 108,500 people living within three slum neighborhoods. Theaverage flow is 360 ips, and the average organic loading is 250 to 350kg/ha—day of 5—day biological oxygen demand (BOD5). At these averageloadings, the primary ponds were operated in the facultative mode, while thesubsequent ponds were eerobic (6).
STUDY METHODS AND MEASUREMENTS
Pond Management
For purposes of the aquaculture studies, the sequence of ponds withinthe lower battery was modified into three series:
o Series 1 consisted of four wastewater stabilizatjonponds (referred to as Pl, Si, T1, and Cl) of whichthe third— (“tercera”) and fourth— (“cuarta”) levelponds were used for aquacuiture;
o Series 2 consisted of five wastewater stabilizationponds (P2, S2, T2, C2, and Q2) of which the third—,fourth—, and fifth— (“quinta”) level ponds were usedfor aquacuiture; and
o Series 3 consisted of two levels of treatment ponds(P3 and S3) and was not used in the experiments (6).
Figure 3 illustrates this three—series pond arrangement within thelower battery. Pond S2 was initially a primary pond and ponds Ti, Cl, T2, C2,and Q2 were initially secondary ponds prior to the initiation of research atSan Juan.
—9—
Figure 2. Map of San Juan Lagoons Showirig Levels of Treatment Prior to theAguaculture Studies
Olviding Chamber P Prlmary LagoonsS Secondary Lagoons
~1) (9) Sampiing Stations
Source (37)
— 10 —
Figure 3. Pond Arrangement during Aquaculture Studies
pf = PARSHALL FLUMEpbf = PALMER-BOWLUS FLUMEdc = DIVIDING CHAMBERrr = IRRIGATION WATER
Source: (6)
— 11 —
During harvest activities at the end of Phase 1, it was realized thatthe existing means of draining the ponds were entirely inadequate for fishculture. Therefore, for Phase II, sluice gates were built to facilitate quickand adequate drainage for harvesting (27). Otherwise, the ponds were notaltered. Because of the time constraints under the UNDP/World Bank IntegratedResource Recovery Project, the sediment that had accumulated at the bottom ofthe ponds could not be removed. As a result, the fish may have been subjectedto more contamination than they would have been otherwise.
SERPAR, under the technical guidance of CEPIS, operated the Series 1and 2 ponds within the lower battery in accordance with CEPIS’s fiow measure—ments and water quality parameters and UNA’s monitoring of fish survival andgrowth. The primary, secondary, and third—level ponds (Pl, P2, Si, S2, Tl,and T3) were operated as continuous—flow ponds with an average depth of 1.3 m,while the fourth— and fifth—leve]. ponds (cl, C2, and Q2) were operated asbatch—flow ponds with an average depth of 1.0 m. Within the batch—flow ponds,only enough treated wastewater was added to compensate for evaporation andinfiltration losses (6).
Selection of Species
The choice of fish for stocking fish ponds depends on the temperatureand water quaiity of the given location in relation to the conditionsconsidered suitabie for the various species being considered. Fish that arereadily sold, bring a good price on the market, reproduce easily, and growfast are ideal. In order to maximize utilization within a pond, cuiture ofmore than one compatible species (i.e., polyculture) might be desirable.
In the Lima study, tilapia were selected for stocking because oftheir hardiness in oxygen—stressed aquatic environments and their recognizedgood taste. Tilapia is a native freshwater fish of Africa. Originallyexported to Southeast Asia as an ornamental fish, it is now the region’s mostimportant pond—cultured fish for food consumption (25). Experience inThailand, India, Taiwan, and Israel has cleariy shown tilapia to be a hardyspecies able to survive and grow well in waste—fed pond systems (15, 22). Thespecies of tilapia selected for these aquacuiture studies (Oreochromisniloticus) is recognized for performing well in fish cuiture and for beingeasily caught by seining (22).
Prawns were selected for stocking because of their popularity withconsumers and potential markec value. The market price of prawris in Lima, forexampie, typically runs 10 times higher per kilogram than the price offreshwater table fish (9). The variety selected (Macrobrachium rosenbergii)is a tropical species that is popular for culturing because it is more tameand less cannibalistic than other species and has a faster growth rate,shorter larval period, and wider range of temperature tolerance (27). Noreference in the ljterature was found to indicate whether prawns could becultured in wastewater—based systems; but experiments have shown that theybenefit when organic matter, inciuding organic manure, is added to their pondwater (9, Hepher).
— 12 —
Common carps (Cyprinus carpio) have a long history of being raised inponds heavily laden with human excreta, notably in China (15). The twovarieties selected for stocking in the Lima study are the “big belly” variety,which is scaied, and the “mirror carp” variety, which is only partly scaled(22). They are able to tolerate harsh aquatic conditions better than theother varieties.
The species of tilapia selected feeds principally on phytoplankton,whereas the common carp is an omnivore that feeds on protozoa, zooplankton,and bottom fauna such as insect larvae, worms, and molluscs (22). Sincetilapia and common carp ~o not compete for food and generally occupy differentzones of the pond, they are well suited for polyculture.
Stocking
Stocking activities occurred in two separate stages of aquaculture.
Phase 1. Tilapia, which had been previously imported to Peru fromIsrael, were spawned. Juveniles were nursed to the fry stage at UNA.
Prawn juveniles were also imported from Israel and arrived in April1983; however, only half survived the long journey and another importationwas required —— this time from Panama.
Just before the ponds were stocked, bioassays were conducted in whichfish and prawns were separately held in cages (about 10 individuals in each)within selected ponds for one week. The bioassays showed good survival underthe pond water conditions upward of 90 percent for tilapia and 75 percent forprawns).
Stocking (tilapia in Ti, Cl, and C2 and prawns in Q2) occurred inJune 1983. The stocking rate for tilapia was 12.2 kg/ha in T1, 5.2 in Cl, and44 in C2, while 450 prawns were placed in Q2. Aquaculture took place over thenext three (winter) months and the tilapia and prawns were harvested in lateSeptember 1983 (27).
Phase II. Some of the tilapia from the Phase 1 activities wereallowed to spaw-n. At the UNA laboratories, the fry were fed on Mesterolona, asynthetic androgen, for the first morith after hatching in order to induce sexreversai and obtain a male population.
Some of the first prawns to arrive for Phase 1 had been selected forbroodstock. After spaw-ning in the summer of 1984, their larvae were reared inspecially designed UNA facilities and the resulting juveniies nursed in UNAtanks for a month.
Common carp fry were imported from Panama. The fry were late and didnot arrive in Lima until February 1984.
Stocking for monoculture of tilapia in Q2 occurred in September 1983and in T2 in October 1983. The stocking rate of Q2 was appreciably higher
— 13 —
than that for T2 (205 kg/ha in Q2 versus 150 kg/ha in T2). Prawns werestocked in C2 in October 1983 at a stocking rate of 4.6 kg/ha —— C2 wasselected because irs water quality was expected to be better than that in Q2during Phase 1 operations. Aquaculture proceeded over the summer months, andtilapia and prawn were harvested from Q2, T2, and C2 in April 1984.
Stocking for polyculture in Cl began with tilapia in February 1984;common carp were stocked in March 1984 and prawn in April 1984 (27).
F Lows
The total sewage flow to the lower battery where aquaculture studieswere conducted was measured continuousiy from May 1983 to April 1984. Stevenstype—F water—level recorders were located over Parshall or Palmer—Bowlusflumes and monitored by CEPIS. The influents to ponds Pl and P2 werecontrolled by two dividing chambers calibrated to provide about 350 Kg/ha—dayof BOD5 to Pl, and 250 Kg/ha—day to P2 (6).
Water level in all the aquaculture ponds was measured once daily byCEPIS. Precalibrated triangular weirs gave instantaneous flow measurements ofeffluents from Pl, Sl, P2, and T2. To complete the information needed tocalculate flow balances, CEPIS also closed inlets and outlets of all ponds fora 24—hour period and measured losses attributable to infiltration orevaporation (6).
Environmental Observations
CEPIS staff recorded daily observations of meteorological conditions,pond appearance (e.g., color, odor, scum, floating matter), conditions ofdikes, and presence of birds, insects, fish, or prawns. A meteorologicalstation nearby also provided data on daily air temperature, wind speed anddirection, evaporation, solar radiation, hours of sunshine, precipitation, andcloud cover (6).
Water Quality Measurements
Every day at about 10 a.m. and 2 p.m., CEPIS measured temperature anddissolved oxygen (DO) in the aquaculture ponds. Polargraphic analysis (YellowSpring Instruments, Model 57) with electrodes positioned at 20, 40, and 60 cmwere used. At the same time, surface pH levels were measured using an OrionResearch, Model 301 pil meter (6).
On a rotational basis (at least twice for each aquaculture pond),CEPIS also recorded temperature and DO profiles every 2 hours for periods of3—5 days. Sets of temperature thermistors and DO electrodes positioned at 20,40, and 60 cm were used with a galvanic cell (Precision Scientific DOAnalyzer) and recorder (Esterline Angus, Model MS 4OIBB). Cycles of pH werealso recorded for each aquaculture pond (6).
From May 1983 to April 1984 CEPIS collected water samples daily atabout 10 a.m. in all of the aquaculture ponds. The samples, which were in
— 14 —
plastic 1—liter botties, were acidified immediately with 1 ml of concentratedsulfuric acid and taken directly to the CEPIS laboratory for analysis of totalammonia nitrogen (NH3 and HN~) by distillation. Un—ionized ammonia levelswere computed using the ~errara—Avci equations with concurrent dailymeasurements of total ammonia, pil, and temperature (6).
During the same period raw sewage was sampled weekly and all pondeffluents biweekly. Composite samples were obtained in two plastic 2—literbottles using a 24—hour automatic sampler. One sample, fixed with 2 ml ofconcentrated sulfuric acid, was analyzed for total ammonia (it was alsoanalyzed for total organic nitrogen and soluble chemical oxygen demand (COD]during Phase 1 of the studies). The second sample was packed in ice duringthe 24—hour sampling period and transferred immediately thereafter to thelaboratory, where it was analyzed for soluble (filtered) BOD5 in pondeffluents and total BOD5 in raw sewage (6).
During Phase 1, CEPIS also measured detergents (MBAS), totalorthophosphate phosphorus, and occasionally total nitrate nitrogen in rawsewage. In Phase II, total alkalinity and phenolphtalein alkalinity weremeasured (6).
Between June 1983 and June 1984, CEPIS took water samples forbacteriologic analysis from all ponds and raw sewage. Samples were collectedmonthly in sterilized 125—mi glass botties. CEPIS analyzed samples for totalcoliforms and fecal coliforms (E. Coli) using multiple tube methods. FromMarch to June 1984, Standard Plate Count (sPC) and Salmonella Most ProbableNumber (MPN) were determined. Salmonella isolates were sent to the NationalReference Laboratory for Enterobacteria in Peru for serotype identificationand antibiotic sensitivity tests (6).
Water sampies for parasitological analysis (protozoa and helminths)were taken quarterly in clean plastic bottles of 1— to 4—liter capacity (6).
All measurements discussed above were performed according to thestandard methods outijned in Table 1. Methods of preservation and holdingtimes are described in Table 2. Data were processed on CEPIS’s microcomputer,with consistency tests and verification routines applied to all dataobservations, and statistical summaries provided regularly to ~JNA forcorrelation with fish growth resuits (6).
Sediment Quality Measurements
Between March and April 1984, monthly samples of sediment sludge weretaken from T2, C2, and Q2, and between May and July 1984, monthly samples ofsediment sludge were taken from Pl, Si, Tl, and Cl. A 2” diameter PVCsharp—edge corer was used by CEPIS to collect the saniples (6).
Subsequently, 50 g of sediment from each sample were mechanicallymixed with 450 rel of buff er solution and were tested immediately for SPC andfor total coliforms and fecal coliforms MPN. Initially the sludge was alsoanalyzed for qualitative isolation of Salmonella. Since resuits were
— 15 —
Table 1. Components of the Experimental Program and Analytical Techniques
Psrams~er. Unit. Frequertcl Anaiytical Method
t. NONBtOI.OGICAj,
A. ~teorolo~ica1
8. Rydraulic
1. Dissoived oxy8ena) Profile (20, 40, 60 cm)b) Diurnal
2. Chemical axvgem demand
3. Alkalinity4. ‘iutrients
a) Organic nitrogenb) Ammonia nicrogenc) ~4itrate nitrogend) Orthophosphats Phoaphorue
5. Detergenta (MBAS)
Twice daily pH meterHouriy during
3—5 daye
Twtce dailyEvery hour duting
3—5 day!Pi—weekly ti~ the
first phase~Jee k 1 y
4e ekl y~Jeek1yOccastonally~Je~k 1 yWeeki v
Ga lvanometrtc/Winklar
‘Joiumetric (potassitas dIchromate)
Volumetrjc (KjeLdahl.)Phocometrtc (Nessier)Cd reduction and diazotatton)Photometrtc (Ascorbic acid)Spectrophotom.trtc methods
F. Biochemical factors
Ii. BIOLOCECAL
A. ‘Licrobiological.
‘g/lmg/L
ng—02/m
2—hr
Electormatrtc methodE1ectrometric inethod
Ga1~anometrlc ccli
Multipie tubes (Lauryl criptose)Multiple cubru (E.C.)14u1tiple tubes (seientce/’4ovobloctne)Concentration; flotation wlth Zn sutfate
and sedimentation wtth formalin—ethet
1. Wind VuloCity Km/h Daily Items 1—5 obtained from anearby meceorological station
2. Wind diruccion3. Air temperature
Degree.°C
DailyDatLy
4. Evaporacion5. Solar radi~Cion
mmgm.cal/cm2—day
DailyDaily
6. Infiltracion mm/day Once Change in level
1. Avarag. flow L/s Daiiy Flow recorder2. Maxtmt~hourly flow 1/~ Daily Flow recorder3. Maximum daily flow 1/s Daily Flow recorder4. W.t.r balance ii, Monthly By calculation5. T..ev.l fiuctuation mm Daily Field meaSurement6. Depth ei Ortce Field meaCuremant
C. Phystcal factors
1. Water cemp.rature °C Electromecric (in eitu)a) Profil. (20v 40, 60 cm) Twice dailyb) Diurnal lourly during
3—5 days2. Pond appearance Qualicative Daily Field obuervation3. ~or Qtialicac ive Daily Field observatton4. Sc~ .nd floacing maccer Quaiitative Detly Ft.ld ob.ervation5. Vegetation om dike Quallcattve Daily Field obeervatton
0. Phystcal factors
t. p44 Unitsa) surface (20 cm)b) Diurnal
E. Chamical faccors
mg/l
eig / 1.
mgf 1.mg/ 1r\g/img/ tng/ 1
1. BOD 20° C, S days2. BOD 200 C, 1,2,3,5,7 days
3. Primary productivicy
1. Total Coliform.2. F.cal coliform3. Salmonella4. Procozos/helmincha
Weeki yJeekly in Phase t
aquaculture pondsOccasionally
‘lon th lyMon th 1 y‘lom th LyQuartet Ly
‘~ ‘JMP~4‘IP Nidentif icac ton
Source: (6)
— 16 —
Table 2. Preservation of Samples and Sample Holding
VolumeParameter required Containera Preservative Holding time
(ml)
a. P = plastic, C = glass
Source: (6)
Alkalinity 100 P, C Cool, 4° C 24 hours
BOD 1,000 P, G Cool, 4~ C 6 hours
COD 50 P, C H~SO4to pH 2 7 days
Dissolved oxygen
Probe 300 G onLy Determinedon site
No holding
Winkler 300 C only Fix on site 4—8 hours
MBAS 250 P, G Cool, 40 C 24 hours
Nitrogen
Ammonia 400 P, G Cool, 4° CH2S04 to pH 2
24 hours
Organic 500 P, C Cool, 4~ CH2S04 to pil 2
7 days
Nitrate 100 P, C Cool, 4° CH2S04 to pH 2
24 hours
pH
Orthophosphate
25
50
P,
P,
G
C
Cool, 4 ° CDetermined
0fl siteFilter on siteCool, 4° C
6 hoursNo holding
35 hours
— 17 —
inconciusive, later samples were assayed for Salmonella spp. and enumerated bythe multiple—tube method. In addition, diluted samples of sludge (200 gsediment mixed with 1,800 ml buffet solution) were analyzed for parasites (6).
Primary Productivity Measurements
CEPIS conducted primary productivity measurements four times inaquaculture ponds Ti, Cl, C2, and Q2 on a rotational basis during hours ofgreatest sunlight. Pairs of light and dark bottles filled with pond waterfrom depths of 10, 20, 30, and 40 cm were suspended at those depths for onehour. Initial and final DO concentrations were measured in the field using aspecific electrode (Yellow Spring Instruments 5720A probe) or in thelaboratory, as needed when DO ievels were especially high, using the Winklermethod. Net photo~ynthesis was estimated as mg/l of net oxygen production andconverted to mg/m~—hrof oxygen by integrating through the water column (6).
Aquaculture Evaluation Techniques
LJNA performed all of the stocking, sampling, harvesting, andevaluation associated with the aquaculture project. Throughout theaquaculturing periods, fish and prawns were sampled monthly by seining, tomeasure weight and length of individuals. A minimum of 3—5 percent of thestocked number from each pond was removed per sample (27).
Harvesting
At the end of each growing period, each pond was drained andindividuals harvested by seining to determine survival and growth. Thefollowing parameters were subsequently calculated from the data on weight,length, growth period, stocking number, and harvest number:
— condition factor (as a function of weight and length),— daily growth rate (as a function of weight and time),— daily growth rate (as a function of length and time),— stocking rate (as a function of weight and pond surface area),— density (number of individuals per hectare of pond area),— yield (final minus initial stocking rate),— productivity (as a function of weight gained per hectare per
day),— firial survival (final number of individuals versus initial
number per pond),— intraspecific competence (as a function of productivity for a
low—density population versus productivity for a high—densitypopulation),
— interspecific competence (as a function of productivity for amonoculture pond versus a polyculture pond),
— carrying capacity (maximum total weight of cultured speciesthat the pond can sustain), and
— critical standing crop (maximum total weight of culturedspecies that the pond can sustain without showing a reductionin growth rate) (27).
— 18 —
Food Processing
Following the Phase II harvest, fish were studied at the IJNA
laboratories to determine the yield of traditionally edible sections. First,some of the fish were segmented into head, gilis, gut, skin, bones, andtail. Each part was weighed and the percentage of the total weight occupiedby each was calculated. Edible yield for several. kinds of cuts (e.g., fillet,dressed, and semidressed) was determineci as a percentage of total weight (27).
Two samples of fish were transported as quickly as possible afterharvest to the UNA laboratories for processing:
1. Fish from Q2 were washed, cut along the back (butterfly cut),washed again, dipped into a brine solution (36.3 percent salt for 30 minutes),drained, layered within salt in a salt:fish ratio of 1—1/2:1, washed anddrained after 3 days, then packed in polyethylene and refrigerated.
2. Fish from TI were washed, cut along the back, washed again,dipped into a brine solution, drained, smoked at 30°C for 12 hours, thensmoked at 600 C for 2 hours, cooled, packed, and refrigerated (27).
Bacteria Measuremeots
Bacteriology studies on raw fish from all the aquaculture ponds wereperformed by USM—IVITA during Phase II. A random sample was taken from themonthly seinings performed by UNA. Samples destined for microbiologicalexamination were placed in plastic 45—liter containers and transported live.At USM—IVITA they were removed from the water and placed live in arefrigerator, where they remained living (although subdued) until analysis.Meticulous sterile laboratory procedures were followed in skinning andcleaning the fish, so that no contamination on the skin, fins, gills, orwithin the digestive system would enter the muscle samples (28).
The first examinations were carried Out on juveniles before they wereplaced in ponds, and monthly examinations were performed thereafter. Muscleand digestive tract content (DTC) were examined monthly for the presence ofbacteria in fish, and at harvest time peritoneal fluid was also examined (28).
The MPN was determined monthly on individuals. Muscie sample size inthe final stages was increased to 65 g to see if large samples would yieldpositive results.
At the time of harvest, SPC (on nutrient, McConkey, and mFC agar) wasalso determined —— again, 65—g muscle samples were used. At the same time,enrichments (in selenite broth and tetrationate broth) were prepared forisolation (on Salmonella—Shigella agar and mFC agar) of Salmonella.Serological tests were performed for plate colonies that showed biochemicalreactions comparable to those of Salmonella. Those that had a positiveserological reaction were taken to the National Reference Laboratory forEnterobacteria for identification.
— 19 —
At harvest, enrichments were also prepared for the isolation ofM—Enterococcus from muscle and DTC, and colonies were confirmed by microscopicexamination (28).
Because the full array of analyses was not performed every month, themicrobiology data are not complete and at this time provide only an indicationof the public health aspects of the aquaculture undertaken (9, Buras).
For purposes of reference, USM—IVITA also examined MPN and SPC ofmuscie, peritoneal fluid, and DTC samples of tilapia harvested from smallaquaculture tanks supplied with clean well water and fertilized byanaerobically digested animal manure (24, 28).
Bacteriology studies on raw and processed fish harvested from T1 andQ2 were performed by UNA. During processing, the tilapia were washed andfilleted by standard commercial—home procedures. As a result, the knife usedto cut open the fish and clean it was also used to do the filleting, and noantiseptics were used for disinfection. Any contamination on the skin andwithin the digestive tract of the fish could therefore be transferred to themuscle of the fish (10). Homogenized samples of fillets with skin, filletswithout skin, and processed fish were evaluated for MPN, SPC, Salmonella, andStreptococcus fecalis (9, Buras; 27).
Parasite Measurements
Parasite examinations were performed by USM—IVITA on fish sampledmonthly and at harvest during Phase II. Muscle, gilis, and DTC were examined.
Gills were placed in a glass jar with physiological serum and thenstirred vigorously. The resulting liquid was observed for monogenea. Thenthe liquid was centrifuged in test tubes to obtain sediment. Each sample ofsediment thus derived and of DTC separately obtained was further centrifugedand processed so that any flotable solid matter (namely, parasites) could beconcentrated and then collected on a slide for examination under themicroscope (the overall process followed is known as the Faust FlotationMethod) (28).
Portions of muscie were pressed between two glass plates and examinedunder a stereomicroscope for metacercaries and plearocercoids. In the eventof a positive result, the parasites would have been separated from the muscieby digestion with pepsin (29).
Fish Toxicology Measurements
CEPIS undertook a one—time sampling of six tilapia fish from Cl inApril 1984. A homogenized sample of all muscle tissue was prepared, of which100 g were analyzed for water content, lipid content, and fixed solids. Three10—g samples were prepared by acid digestion and extraction for mercuryanalysis by wet vapor atomic adsorption spectrophotometry. Three 5—g sampleswere analyzed for lead, chromium, and cadmium using atomic absorption spec—trophotometry (6).
— 20 —
Subsequently, 2g of lipids were extracted from 500g of the homo—genized sample for qualitative analysis of organochiorinated and organo—phosphorus pesticide using methods prescribed by the U.S. Food and DrugAdministration (FDA). A portion was also prepared for analysis by gaschromatography using AOAC methods for identification and measurement oforganochlorinated pesticides (6).
— 21 —
Chapter 4
FINDINGS
HYDRAULICS AND LOADINGS
CEPIS determined 8 daily water balance for each lagoon and computedhydraulic loadings. Table 3 summarizes the fiows entering each pond, pondarea, depth and volume, estimated infiltration rates, and nominal hydaulicdetention time (6).
The hydraulic detention times shown in Table 3 are somewhat over—estimated with respect to real detention times, since considerable short—circuiting occurs in the ponds. According to earlier tracer studies conductedby CEPIS at San Juan, real detention time is probably about two—thirds thenumber of days shown (6).
Table 3 also shows the daily estimate of average BODs and theresulting average surface loading rate per pond. To calculate the averageBOD5 loadings in the ponds, the average flow for each pond was multiplied bythe corresponding BOD5 concentration interpolated from weekly sampling results(6).
PHYSICAL—CHEMICALWATERQUALITY
As part of the water supply and sewerage master planning effort, thewater quality of the main interceptors was analyzed for a number of para—meters, including heavy metals (16). The results indicate that the overallquality of wastewater in the main interceptor of the south is markedly betterthan that of interceptors in the north. This difference reflects the limitedindustrial development in the southern region of Lima, where the San Juanlagoons are located (16).
Earlier studies uridertaken by CEPIS at San Juan (lagoons located inthe southern portion of Metropolitan Lima) to develop stabilization ponddesign relationships showed a high correlation of removed 5—day biologicaloxygen demand (BOD5) bad versus applied BOD5 bad for the primary andsecondary ponds of San Juan, a strong correlation between total BOD5 andsoluble BOD5, and a relationship between COD and BOD5 (37, 38).
During the aquaculture studies, raw sewage loadings were bower thananticipated (kg—BOD~/ha—daywas 333 in Pl and 201 in P2, versus expected loadsof 350 for Pl and 250 for P2). CEPIS found the average boads removed in theprimary facultative ponds were 307 kg—BOD5/ha—day in Pl (92.2 percent removal)and 188 kg—80D5/ha—day in P2 (93.5 percent removal). The loads removed indowngradient ponds were: 70 percent in Si, 45.8 percent in Ti, 66.4 percentin S2, 47.5 percent in T2. These were lower removals than CEPIS hadexperienced in earlier studies and were attributed to the reduced bacterialbiomass in advanced polishing ponds. In any case, multiceil pond systems
— 22 —
a.b.c.d.
Source: (6)
Table 3. Hydraulic and Organic Loads on Ponds. Average Values
,
May 1983 to April 1984
Pond[nflow
(ips)
Area
(Ha)
Averagedepth
(m)
Volume
(m3)
Infiltra—tion rate
(mm/day)
Hydraulicdetention
(days)
InfluentBODÇ(mg7l)
SurfaceBOD~loada(KG7Ha—day)
Pl 29.7 1.20 1.3 15,6007~6b 6.1 155•7c 333•2c
Si 28.8 1.44 1.6 34,040 3.7 9.3 12.6 21.6
TI 28.1 1.49 1.3 19,370 6~1b 8.0 11.7 18.0
Cl 2.0 1.30 1.0 13,000 13~1b 20.9 2.5
P2 15.3 1.10 1.3 14,300 19~2b 10.8 155•7c 201.0c
S2 12.8 0.88 1.3 11,440 14.1 10.3 10.6 15.5
TI 11.4 1.30 1.3 16,900 18.0 17.2 10.4 6.7
C2 1.2 0.49 1.3 6,370 10•0b 18.7 3.9
Q2 0.6 0.53 1.0 5,300 10•0b ...d 7.8 0.9
Average of computed daily loads.Estimated (37).Total BOD5, other vaLues are solubLe BOD5.Operated as batch—flow ponds.
— 23 —
should be designed so that primary ponds serve mainly for BOD removal, whilepolishing ponds are used principally for pathogen control (6).
Table 4 summarizes the average daily DO, temperature, pH, and totalammonia nitrogen levels for the entire study period, May 1983 to April 1984.Tables 5 and 6 show the averages and ranges of these same parameters forPhases 1 and II, respectively. The CEPIS report provides graphic presenta—tions of daily measurements, as well as raw data, monthly statisticalsummaries, plots of monthly averages, and diurnal patterns for DO andtemperature (6).
Table 7 provides average weekly data on BOD5, total ammonia nitrogen,organic nitrogen, orthophosphate phosphorus, total alkalinity, and detergents(MBAS). More detailed information (e.g., detailed statistical information,raw data tables for each pond effluent, and probability distribution curvesfor each parameter) is available in the CEPIS report (6).
In February 1984 water quality chariged dramatically as a result of anaccidental upset in the operation. Adjacent farmers tampered with pond inietsluice gates, without authorization, in order to let large quantities ofwastewater through to their irrigation channels. A shock bad of secondaryeffluent entered the T2 pond and thereafter was feit (but to a lesser extent)downgradient in C2 and Q2. Weekly data revealed that soluble BOD5 levels inT2 shot up to 44.9 mg/l compared with the average 18.7 mg/l. Surface loadingafter the incident reached 20 kg—80D5/ha—day in T2 compared with the averagebad of 6.7 kg—BOD5/ha—day (6).
Dissolved oxygen is a key parameter in aquaculture. As expected forwaste stabilization ponds, phytoplankton photosynthesis caused supersaturatedDO conditions during most afternoons; and nighttime biomass respiration ledto a reduction in DO so that bevels were near zero by the early morning.Nighttime DO levels were bower and remained low for more probonged periods inthe tertiary ponds. As a result, the fish probably experienced oxygen stressfor short periods each day, a factor that could have limited their growthpotential. As Table 4 indicates, however, the overall average DO levels inthe San Juan aquaculture ponds were sufficiently high (well above 2 ppm andoften reaching 10—15 ppm in the afternoon) for the survival and growth of fishand prawns (6).
Earlier CEPIS studies had shown primary and secondary ponds to haveonly limited nitrification potential (37,38). Batch operation of the aqua—cubture ponds showed 1.5—2.1 mg—N/l total ammonia nitrogen (NH3 + HN4~), whilecontinuous—fbow tertiary ponds averaged effluents of 8.3—11.6 mg—N/l. Duringaquacuiture studies (see Tables 4 and 7), total ammonia decreased progress—ively through both series of ponds. This was due to biological uptakefollowed by sedimentation of organic nitrogen, control of surface loadingrates through batch operation, and possibly to leaching into pond subsoil (6).
— 24 —
0’—4
~-11.4
0
0’
0).-1
-4‘-4
~4-10
1.40)
0
00.
0)8..
4.)-4
t)
‘-4
0‘-44.)
“-4•000
‘-4
4.)
0)E
014
‘-4
.4.
0),-1
Ei
0) ~‘-.4
...4 ~‘.,
l~ QZOEI
“-4 E ~01 ~E~ S—..
~ -.4,-.1 .‘.I ~
IJO I08~0
~ S-,
0.
E0
.-‘ 00 “00
E0) 01~.~ 04.) .4’
41) E0. 0E41) 0Ei e.i
E0
0~‘ “0.-1-S-
bO EE 0
S.—
0o •~
E0
0CN
00.
00000
..o-im~’r~ ~o~r~ir~
.-i c”a ~ -i .-i .-i e’~~ — ‘.-i.-4
‘.-4~0ifs CNr-u~.-40
0Da30:7 Q~0~0’~
‘-4 ~ ~.4. IS- 0’. -.4 11’. 0
e.sr~ ~0s1Lr~4c”~C’.IC’~’d
C’4u~C’I’C 0C’.4QOø
~CflSdC43C’.5 e’1iflF’--~U”.e.i~c’j C”JC’4~
(‘,1 ir, c-’J .~ U~ CN .4’ — ~ 0
~c~r Cirru~~Cc’~r~C”~C’4 C”lC’.JC_’l
~.o.~cOr’-c’~, 4If~~
-4r’.8-4mc’.~ ~_uI,,-I1”.
a’.~or~-m0 C’~C”)C’.’.-4~0
‘.~~)CS.J.4.C~ ~‘.).~4Q’.‘-4-4
5o~omcnc•.i~U”.s~ r’-.-i’,0Cfl~
.-4 -4 -.4 .-in0
b~ 0c
‘-4n8..
n 0)8.. 4-)0Z
.-4’4C’~’1C”iE40H00’
~#4‘~
IC”1C’~~E’oEiUO’
—S
‘.0S-.
0)01..
0t,,
— 25 —
4-40
1..0)4-)0)
to14to0.
-4to0
“.lE0)
0
to
-4tot)
‘-4
0.
8..0
L4
0)
toIi0)
to
0)
to
0)-4.0toEi
0)
to
0.
‘-4
‘00)‘01.4000)
00.
41,14
4-’-4
0to
0’.‘-4
Ii0).0Ê41,1.)0.0)
t,,
01.)
-4‘-4
140.cl:
‘00.0) 0.P~
--4
0 «-4
10
to
to‘-4
0—S
0.
to.4-’0Ei
00
1-.0)
00
‘-4
110x
00
1..41)4-)
4.4
~b0‘-4
140x
000
01 ~‘~ Ii
0)
1.4 ‘4-4
4-’to1.40)00
6 ‘-4
Eil-.0x
‘0
00.
.4.0’ 0 0 ~ ~ — 000F” Is C’.’. .40’ 0 sd~ 0
Cr40 000 000
Is C’10’.OI/’. ‘.0 C~ ~ ‘.0 ‘-4 I1~~~ t’.)
0’. “0 0 Cd’) 0 0 ‘t’. 0—--4
~I0’i~ ‘,O’,Oir, OC”IO
~ ‘.0 ~ 0 ‘0 0’. 0’. r-.-4
0’.’f%00 rne’,o 1-99
r.-00%0 ~0’.0 000’.r--4
m0u~ 0.00
‘.0-40 .—40.-I -400cS.J -4CN
0’. 00 C•’l ‘t’. 0 It’. .4’ 00 -i
C’,1.-I0 I4~0’.0 r’-LflO—
u~’.ii~4 -490 C’,iIr)0
.-4.40’. c’.ir-o’. c-ir-0C’~4-4 C4C”1~-4 CJC’,IC’$
-40000 C4’sOC’l
0 (‘100 -I .4’ IS- -.4 ‘.00’.~ ~C’~l-4 CslC’4-.4
41)66 0)86 0)00~i ø0~~ 00toEE toEE ~881.i”.4’r4 14..-4.,-4 14’.-i.,-lo)Mn ~ W~4~~~‘.-4 ~to~.-4 ~to’.-4•cl:zx <xx <xx
‘-S
‘.0
1-
0)08..
0t,,
— -41 1
Ei 0 0
— 26 —
4-40
I..i0)4-,0)8to1-.to
0.
-4to~~1
‘-4
80)’.00
‘0
to
to0
“-4ul
.00.
1..0
4-4
41)
to140)
‘0
to
41)
~0
41)‘-4
.0toEi
‘—4
‘—4
0)
to.00.
‘-4
‘00)‘011000)
‘0
00.
41)14
4-)‘-4
t)to
-1~000’.-4
‘-41..0.
04-’
en000’
‘-4101 ~S— 14
41)0)~)
1,Ito1-.0)00
8
E-41-i0x
‘0
00.
.—4C’.J
‘t’. (“.00N.0’4.-4
000’. 0en 00-4
0~t’. (‘4‘000
0 ‘.0 —-~ ‘.0 0
0.—’ 0 ‘-4 (fl0 0 (“1 0 0 c4 0
.4’ 0 41’~00 “400
Is 000.40’. Is
~‘ en 0IS- .~ (‘4
(‘4 00000 (‘4
(‘400 N”.OO-4
.-4~~Q .-41f)0
0000
0’. Is
1-00
0001-
— ‘.0.4’
0’. 01-
-I in”0
0’ 01--4
(1’. ‘-441’. - C”I 0 t”. ~-J (‘1 IS- .0’ Ir’.
000’ t-’ 000% t- 0’. 01--4
0001--4
11’. ‘0’ ‘.0 in 04fl ~.l 41’. 00 0-400
00’-’ ‘.0en c’-iIs Cfl 0c”i en c’4
Is -40(54 en ~4
Is -10’.~4 en —
(54000
‘.0 IS- Ir)C.4C’.1C54
0000
.4.000C”4C’4CN
00I1’.0’.
.4’ 000%(‘4C”I.-I
.0’0041”.
4.0000C’4C’l.—
41)88øOiitoEE14.,4.,4~~to’.-4<xx
4)8800i~toEE14.,.4.,.~
to~n)to’-i<xx
0)88~toEE14.-4,-~WMn~to’-I
<xx
0)00toEE14’.—i..-40)~4~~to’-4<xx
‘.000 I1’.00
irioen-.4(54
‘4000
.0’--4(54
en’.o~1fl ‘4’ 0
-4
‘40(54
‘4-40(.4
00 ‘.0 en
-4 -4
‘-S
‘.O
Is(.4S-’
0)014
0t,,
-4 (‘41 10 Ei
(54
&
— 27 —
4110)
‘-40.Eto
t,,
-4
0)0)
4-40
41)00tol~-40)
‘0
00.
‘-4
0‘-4
4-,-4‘0
00
-4to1~I
0)8
01-.
‘-4
r~i
15
0)-4‘0to
Ei
.0’000’.-4
-4‘-4
140.
en~00
-4
toxi
>5
1,)-l
‘-4—4to
‘-4
t,,
.0’00.
—S
-4
006
5—
z
Ii
0
‘t
z
11’.
000
‘0
00.
in in 0’. 00 0 -0’ ‘.0 0’. ‘.0 (54
0 41’. ‘0 0% — — in ii’. ‘.0 —Is — 0’. 00 .0’ ‘.0’ 00 en — C~(54 (‘4 — -4 -4 (‘4 -4 _4 -4 -4
00 (“1 ‘.0 (‘4 ‘0’ 11’. 00 en in 00
-4 -4 -4 ‘-4 0 —4 -1 .-‘l 0 0
0 en in — ‘.0 en in 00— 0 Ir’. — -4 in -0’ Is
. 1 1 . . . . . . .en -4 0 0 0 0 0 0
-4 — 0 00 Is ‘0’ 00 0 in 00S S S S ~ S ~ S ~
00 (‘4 (‘4 0’. 0 .0’ 0’. 0’ 0 0-4 .-I ~4 -4 _l -4 -4
— en ‘0 0 (‘1 0’. ‘.0 00 (‘4 —en c-~ -i — -‘ -i
Is ‘.0 Is 0’. 4fl ‘.0 .0’ IS- 00 00
,in c’4 -.i 0’.0~~ 00 t-~ ‘.0in —4 ‘-4 (‘4 -.4 .-l .-4 .4-4
1,J
0)~ .-1 ,—4 ,—1 ,-4 (.4 (54 (54 (54 (‘4
-I 0. Cfl Ei 0 0. c#~ Ei 0 0’4-4
‘-4
-.5
‘.0
0)t.)1-’
0t,,
— 28 —
An’.monia (specifically, un—ionized ammonia, NH~) can be toxic tofish. Toxicity is most severe when pH is high (particularly in the lateafternoon when pH rises as a result of photosynthesis activities), becausemore of the total ammonia is in the un—ionized form. Furthermore, thetoxicity of un—ionized ammonia is proportional to temperature (fish are 50—100percent more sensitive to NH3 at (30°C than at 20°C) (6). Therefore, it wasrecommended that aquaculture not take place in ponds exceeding a maximumallowable un—ionized ammonia concentration of 1—1.5 mg—N/l (9, Hepher).
As indicated in Table 4, the average levels of un—ionized ammonia inthe ponds studied were generally acceptable. But, after the accidental shockloading into the Series 2 ponds, un—ionized ammonia levels went up ——
significantly in T2, but to a much lesser extent in downstream ponds C2 andQ2. Immediately after the incident, the daily values of un—ionized ammonia inT2 exceeded 2 mg—N/l, while in C2 and Q2 daily NH3 concentrations rose to 1mg—N/1 (6).
Heavy mortalities of tilapia occured in T2, whereas tilapia in Q2appeared unaffected; in addition, all of the prawns in C2 died. Thus itappears that tilapia will grow and survive if total ammonia is maintained atle5s than 2 mg—NI1, average un—ionized ammonia is less than 0.5 mg—N/l, andshort—duration levels of un—ionized ammonia do not exceed 2 mg—N/1 (6).Prawns are obviously a much more sensitive species, but not enough informationis available from the studies to indicate how stringent their un—ioriizedammonia criteria should be.
Detergents can be toxic to fish, the lethal level depending on thefish species. Experiments carried Out in Israel have suggested that thecombined concentration of alkyl—benzene—sulfonates (ABS) and soft long—chainbenzene sulfonate (LAS) should not exceed 1—1.25 ppm in aquaculture ponds (9,Hepher).
Detergent removal rates at the San Juan lagooris were found to belimited (largely because of foaming at pond outlets). But fortunately thedetergent levels in the raw sewerage were low (1.0—1.5 mg/l MBAS) (9,Hepher). As Table 7 indicates, detergent levels in Cl, C2, and Q2 were not atdetrimental levels, whjle those in Ti and T2 were on the borderline of being~tressful to fish.
MICROBIOLOGICAL WATERQUALITY
Earlier studies by CEPIS have clearly shown that the removal of fecalcoliforms increases with the time that wastewater is retained in the lagoons.In the c:ntinuous_flow tertiary ponds, fecal coliforms died off to levelsbelow 10 /100 ml. For primary ponds, the constant die—off rate for fecalcoliforms averaged 0.740 1/days, and for secondary ponds it averaged 0.9341/days. Salmonella exhibited similar die—off rates of fecal coliforms (39).
Measurements of total coliforms and fecal coliforms during theaquaculture studies showed comparable resuits. Figures 4 and 5 demonstrate asteady decline in both total coliforins and fecal coliforms in successive
— 29 —
ponds. Overall fecal coliform removals averaged 99.99 percent in Series 1ponds and 99.999 percent for Series 2 ponds. Raw data, statistical summaries,and plots of individual observations for the entire study period are availablein the CEPIS report (6).
Geometric averages for fecal co1iform~ in the fish pot1ds, expressedin MPN/100 ml, were: 2.9 x 1O
4 in Ti; 2.3 x 10 in Cl; 1.7 x 10”- in T2; 5.1 xio2 in C2; and 1.6 x io2 in Q2. During the period of excessive loading inFebruary 1984, a peak value close to io6 MPN/100 ml occurred in pond T2 (6).
In earlier CEPIS studies, fecal coliforms proved a reliable indicatorof the removal of Salmonella from the San Juan ponds (39). A few samplingsduring the aquaculture studies confirmed expected reductions in Salmonella onthe order of 99.99 percent. Serotyping showed survival of S. paratyphi B ineffluents of Ti and Cl (6).
In previous studies, all serotypes of Salmonella encountered withinthe ponds were resistant to the majority of antibïotics tested (39). Theseresults are of some concern with respect to wastewater treatment and reuse,because resistant bacteria of one type can transfer their resistance tobacteria of other types through conjugation. Moreover, bacteria that areresistant to antibiotics also tend to be resistant to other physical andchemical factors, such as chlorination (9, Buras).
Table 8 shows the frequency of positive identification of parasitesin each pond effluent (6). The results support earlier studies performed byCEPIS showing that parasites are largely removed from the water column duringprimary treatment.
SEDIMENT QUALITY
Total coliforms and fecal coliforms in pond effluent and sedimentswere assessed during May—June 1984. Figures 6, 7, 8, and 9 show thecomparative resuits, which indicate consistently higher coliform levels in thesediments than in the pond effluents. Concentrations in sediments were two ormore orders of magnitude greater on the average than in effluents (6).
Figure 10 shows Salmonella concentrations in pond effluents versusSeries 1 sedimento. The serotypes identified are shown in Table 9 (6). Notethat some of the Salmonella in the higher—level ponds could have been added bywater fowi attracted to the ponds by the fish (21).
Standard Plate Count results for raw sewage, pond effluents, andsediments are shown on Figure 11 (6).
USM—IVITA examined the pond sediments for parasites. They foundsignificant numbers within the primary pond sediments, as was expected, sinceparasites are known to settie within 3—6 days (23, 33). In addition, theyfound amoeba cysts within the sediment of Q2 —— probably because thesepersisted in sediments remaining within the pond from earlier times when Q2was a highly loaded secondary pond and there had been a known breakthrough ofparasites from the preceding primary pond (6, 10).
— 30 —
8
7
6
5
4
3
2
0
Figure 4. Concentration of Indicator Bacteria in Pond Effluents, Series 1
:
Geometric Average of Monthly Measurements, March 1983 — June 1984
Source: (6)
8
7
6
5
4
3
2
0INFLUENT POND P2 POND S2 POND T2 POND C2 POND Q2
Figure 5. Concentration of Indicator Bacteria in Pond Effluents, Series 2
:
Ceometric Average of Monthly Measurements, March 1983 — April 1984
E00
2
0
00
0-J
INFLUENT POND Pl POND SI POND TI POND Cl
E00zt,-
000
ci,
0-J
Source: (6)
— 31 —
.04-’
‘-48
-441)
‘0
to
to0
04-’0“4
0.
0“—4“40)4-’
‘4-40
0‘-4
to0
‘.-l4-4‘-4
4-4
0)‘0‘-4
41)
‘-44-’
“—4
00.
4-’0
t)
0)
0)‘.4
00
0)-4.0toEi
-0’000’.-4
-4‘-4
0.
0
en
-4
tOxi
(‘-40’
1.) (‘4no0)
-44-’‘4-4(544)E-4
(“1
0)‘-4 (‘4
0)t,,
(‘40.
-40
0,4-)
0)~ —
4-’4-’41)
-4-4
411 CJ~0)
‘~1‘.-I
0)t,,
-40.
0)00
~to
0,
801
-4 .-4 -4 -4 -4 -4 -4 -4S— S-~ --‘ -S~ -S~ — S- ~
00 00 0 0 0 0 0
(‘.1 (“1 (“4 (‘1 (‘4 (‘.1 (“’1 (54 (‘4‘S— ‘S -~ — •S-S ~S5~ , ~00 00 0 0 0 0 0
en en en en en en en en en--S --S --S --S —S -S’S ‘S- S-
00 00 0 0 0 0 0
en en en en en en en en en‘, ~ S- ‘S-S ‘S.- — -S- S-~ S-,,
00 00 0 0 0 0 0
enen enen en en en en en-S- S-- S-S--S ‘S-S 5~ 5 — —
00 00 0 0 0 0 0
en in in in ,,-‘. in in in in~‘S5’-S~ 5 55 S-S —
00 00 0 0 0 0 0
lfl.t .0_t -0’ -t .0- ‘0’ ‘0’‘S’- S-. ~5 “S ‘S- S-,00 00 0 0 0 0 0
‘0-_t ‘0-_t ‘0’ ‘0- -? .0’ -t‘S-S ‘S-S ‘S-S ‘S-S ‘S.,, ‘S- ~S- ~ ‘S
00 00 0 0 0 0 0
‘.O’,O ‘.O’.O ‘.0 ‘.0 ‘.0 ‘.0 ‘.0‘S S- S-,’., ‘S- ‘S’. S- ‘S- S-,
—— 00 0 0 0 0 0
0000 0000 00 00 00 00 00-S’S—S ‘.SSS S-, ~ S-, ~
0000 -4’,O 00 — in en Is
to to--‘‘-II to
‘00..-4 to to to lol toalE0.ntoln ‘-4~4’.i ÈW 1..-’to 01 —4’.-I--i 411 01
~1 to to”-41X to’-4 4~I.-4 ~
to .0’0IJItO’0.00114 .0 014.00)0 to0)0)>’.lEO)oltoO 4-1 ol0~0—4to‘.-40Q.--1’.-IOIJE0, 0o ‘0E6O~—’6~0w “-4 1414.01404-4 14totoi-’Oto’0E 8 to.00i-J ~0 to 1-4 1,) ‘0’0 ‘.-I .-4 0 ‘-414 ‘-400 00 .0 0) ~ 14
0. t.D~z) ~z~-i 0 < Ei ~
41)0
‘-44-441141)4~10-4
0
.0
0).04-)
000
-~11~I--4
‘0to
>5 ~‘S’
-4 ‘.0,-, 5—
to
0 0)z t-’
11
• 0to t,,
— 32 —
11
10
9z0.
E
0000~4—
3
2
0
Figure 6. Total Coliforms in Pond Effluents and Sediments, Series 1: May—June1984
Pl SI TI Cl
Source: (6)
— 33 —
11
10
9zt,-
T2 C2 Q2
Figure 7. Total Coliforms in Pond Effluents and Sediments, Series 2: May—June1984
Source: (6)
— 34 —
11
10
9zt,-
ci,
E
86
0050
0
Figure 8. Fecal Coliforms in Pond Effluents and Sediments, Series 1~ May—June1984
Source: (6)
Pl SI TI Cl
— 35 —
11
10
9
z
c’~
E
0ID
2
0T2 C2 Q2
Figure 9. Fecal Coliforms in Pond Effluents and Sedimenta, Series 2: May—June1984
Source: (6)
— 36 —
501
04E003zt,-~ 20IDc0E
0ID00
Figure 10. Salmonella sp. Concentration in Pond Effluents and Sediments~ May
—
June 1984
(6)
RAWSEWAGE Pl Sl TI Cl
Source:
— 37 —
— (‘4(54(54 (“1(51 (‘40 S-~ S-, S- ‘S- ‘S- ~
000 00 001 to
‘-40 1~0) — (.4(54 (‘-4 (‘.4 (“1 (‘.1 41)E Ei ~ ‘SS-, “~ 4-1
41) ‘-4 — 0 0 01 0 0 0‘0 to0) .0
1,4 0, 00 4 (54 (‘.4 (54 (‘4 (54 (‘4 1414 ‘0 (0 S-
5 ‘S- S-5 ~ S-, S-, 4)4) 0 (“100 00 — 1.1
0 00.
to—4 (‘.1 (54 (54 (“1 (‘4 (‘-‘1 14
—4 0. ‘S’.,S-,S-, S-.S-. S-’ 00) ‘—400 00 —
g >58 1.-’
0to 1-4
t,, to— ininin LflC’1 ifi 14
4-4 0 S-S-S-S ‘S-S- S-. 0o ‘-‘00 00 0 .0
to0 010 4.1
‘~4‘0’ 0 — (‘-1 (“1 (‘-4 CNin (‘-4 0)00 0) Ei s- S-, ‘S’,, S S-, S-, t)
to 0% — 0 0 0 0 — 00— .—i 0)
‘-4 ‘-4-1 ‘.44-10) 4—i 4)‘-4 0 0) —4 (‘.1 (‘.1 (54 (54 (‘4 (‘4 4-4
(0 ~ -S,, ,~,,, ~,,, t,
0 ‘0 (‘40 01 0 0 00) 0‘00 0~44~1 0. to
— enenen enen en 00. S-, S-- S- S- S-5 S-.. 0
» 0 en 0 — 0 0 (“1‘-414 1,4
to0, 0)o 00 0)0. .0
to 1fl 1fl in in in 1fl 4-14-4 ~ 41) — ‘.. S-, S-, S-, S-,0 01 en’4~ —‘—4 — 8
0140 ‘+4
0 0.0) 01
0 4,4
$4 -4— (“1 ~-l0) 00 000000 00 014 0 01
14 4)0) Ii0,
>50’ 14
to4) 0
014to ‘.4.4.. 4)~ .,.4 .S,
Ei 41) .0141 ‘0.0 —4 ‘.~0. ~.. ‘.40 ~..11 41) ._‘
>5 Ec’.i ~W 141 144,4 ~1.,4 0).-4 01 0.0 tO.0 IJO 0.114 14 in Oto 0)0) to 014 0) .. 0
Cfl 4,1_t EO 0 wS S • • S ~ 0 0
cflCncl, cl)cl~ t,~ Z ~
— 38 —
9
8
7
6
5
4
3
2
0RAWSEWAGE
8
7
6
5
4
3
2
1
00~0)
000
0-J
Figure 11. SPC in Pond Effluents and Sediments May—June 1984
Pl SI TI Cl
T2 02 Q2
(May June 1984)
Source: (6)
— 39 —
AQUACULTURE RESULTS
The main objective in Phase 1 of the aquaculture studies was toassess whether survival and growth of fish and prawns appeared likely. InPhase II, the objectives were to further assess growth and to begin assessingoptimum carrying capacity and stocking density of the ponds. Phase 1consisted only of monoculture studies, whereas polyculture studies werestarted during Phase II.
Phase 1 took place during the winter season (June through October1983). Survival and growth of tilapia during Phase 1 were good (see Table10), despite the relatively cool temperature of the water (it averaged about22°C). About 83 percent of the fish survived in the most contaminated pond,Ti. Survival was 97 percent in Cl and 84 percent in C2. Final growth rateswere 0.85 g/day for Ti, 1.17 g/day for Cl, and 0.79 g/day for C2 (27).
The fish densities in Ti and Cl were similar; however, tilapia in T1,which started at 7.7 g, reached an average weight of 106 g, whereas tilapia inCl reached an average weight of 147 g even though it started from a smallersize (2.4 g). The difference is clearly attributable to the poor quality ofwater in T1; in particular, oxygen 1ev-els in T1 were often sufficientlydepressed to stress the fish and cause them to eat less (27).
Although the quality of water in Cl and C2 was similar, C2 was muchmore densely stocked (4569 fish/ha in C2 versus 2,006 fish/ha in Cl). C2showed the highest stocking rate (746 kg/ha) and highest growth rate (3.8g/day) about midway into the aquaculture period. However, fish experienced anegative growth rate in the final stages, probably because the pond reachedits “critical standing crop” —— that is, the maximum weight of fish that couldbe supported by the natural food in the pond. At harvest time, fish in C2weighed an average of 89 g, whereas those in Cl reached 147, even though thosein Cl were initially smaller (27).
Prawns at San Juan exhibited good growth rates (0.4 g/day), whichwere comparable to those of prawns raised in clean water ponds just a few
miles away at La Molina (see Table 11). Apparently water temperature was amore significant factor in prawn growth than differences mn the quality ofwater in the freshwater and wastewater ponds tested. Prawns raised in cleanwater ponds of much warmer teinperatures (at Satipo) experienced a much highergrowth rate (1.2 g/day) (27).
Harvesting conditioris led to a significant mortality among theprawns. The pond had previously been used for secondary treatment and beensubjected to very high loadings, which had left a thick layer of sludge.There were unanticipated difficulties in draining the pond; and, afterpartial drainage, the embankment had to be cut down to allow completedrainage. The prawns were subjected to shaltow pond conditions and asignificant deterioration in water quality just prior to the harvest. As aresult, all of the prawns died and only 10 percent of the dead animals couldbe recovered from the thick sludge (27).
— 40 —
c-.lCs iI~ �54
1~ ‘~q,a~1cc
~
i~(i~ �‘4~
,~ I’S
C’1~N .~-‘.D‘4-,
~l’~ V’~
r~o 1 lcI’~~l III$4 ‘4—,4J08‘4 ~l ~
~‘4 ~ ‘.0
0) 1’+1 1
-4 is, (“4 4’- (“4
~I(4OC54 ~~lI’4 ~
-4 is’1,4 1
~ ,,-(‘,~II-’l~t—
to. 1 i ~ III
-~
0 I~ (54
cr4 — cr4
qq1~, ,-:~“;
01 cc
oq’4’4~ ~ cl-,1 -, -. ,~ 4,, — II, (S.~
-‘. (“4 U’ (‘4- 0 -~X -‘—4 IS,ïL,~
-,
Ii.0
Ie
1 .51
~‘~H 1 •~: ~~ .t~.1 ~
.~ ~ • (1-~4J
~.8 ~
— 41 —
Table 11. Summary of CrowthPhase 1
Data in Prawn Assays
Place San Juan La Molina Satipo
Average size (cm) 5.86 6.53 8.90
Average weight (g) 3.91 6.22 7.60
Crowing period (days) 88 94 60
Daily growth rate (g/day) 0.405 0.533 1.23
Daily growth rate (mm/day) 0.315 0.274 1.12
Date of control Sept. 6 Sept. 15 July 21
Average water temperature (°c) 21 21 29
Source: (27)
— 42 —
Phase II took place during the summer season (October 1983 throughApril 1984), during which time pond temperatures averaged about 27°C. Duringthe first 3 months after stocking, the growth rate of tilapia in T2 wassimilar to that of tilapia in Q2 (27). (Note that water quality in all theponds during Phase II was better than during Phase 1.)
With the accidental shock bad to T2 in February 1984 and theresulting changes in dissolved oxygen and ammonia levels, significantmortalities occurred. Only about 40 percent of the tilapia in T2 survived(27). On the other hand, about 88 percent of the tilapia in Q2 survived ——
this rate is comparable to the survival measured in Q2 during Phase 1 (27).This high survival is due to the batch operation of Q2, which signîficantlyreduced toxic ammonia boads (6). When the fish were harvested, they bookedhealthy and vigorous (9, Buras). (See Table 12 for harvest results for PhaseII.)
Polyculture within pond Cl was unaffected by the accident in theSeries 2 porids. Monthly control samples indicated good growth for tilapia(2.70 g/day), big belly carp (3.55 g/day), and mirror carp (7.24 g/day). Infact, tilapia grew much faster in the polyculture ponds —— probably becausewater quality remained constant in Cl in contrast to that of T2 and Q2. Theresuits clearly indicate that tilapia were not competing with carp for food(see Table 13).
None of the prawns in C2 survived (27). Die—off could have beenbrought about by a combination of factors, since water quality in C2 was verypoor even before the accidental shock loading occurred. In fact, NH3 and pHwere at their worst levels one month prior to the accident, possibly becauseof the increased algal activity of the early summer. Therefore, the possiblecauses of the die—off of the prawns during Phase II inciude:
o excessive total ammonia concentrations because of accidentalshock loadings of raw sewage to pond series;
0 excessive NH3 concentrations because of increased phytoplanktonphotosynthesis and, hence, higher pH in the summer months
0 low nocturnal DO because of shock Loading of raw sewage; and
o bow nocturnal DO because of high benthal (sludge) oxygen demandand high summer temperatures.
Tilapia had been sexed prior to being placed in Q2. Nevertheless,there were some females and they spawned. The pond thus yielded a largeproduction of fingerlings at the time of harvest, almost equivalent in totalweight to the weight of large fish. The fingerlings that were caught wereplaced in another pond for stocking subsequent fish culture operations. Thestocking rate for this pond had been higher during the fourth month ofaquaculture than at the time of harvest. Apparently the fish experienced anegative growth rate in the final month because of the unexpectedly highdensity caused by the small fish (27).
— 43 —
0 ~ m -~1 1
c’-l~
-~(‘1 (“1~ -~i~N,0104~,4 0
~ (‘~i~-~ -~ ~0— -i’ — — —~1 (‘4 1 -~‘f4
-~ ~
414 ~ -~ — 0 —‘ ‘0 ~‘-4 4_4 r’1
S— ~
~ ~14 ,~ -E ~m m ~m
0’-(“4
o ~c—~ ‘o~
0’
8 “-54t~0-,c.~0 “4 0”14 o’~~-id--c~o, ~
0’‘V — —
~4-4 - ,‘~0_~I I~0~
WO) .4‘-4 ~(‘4
-4 —4rm
.T—o’i1 00 1 1 (‘1 ~4
01’C01’~ 1’—
,~ ~—dc~- ‘0’’r- t
—5-11
~W —1 ~ 1 -~‘44 1 ~0 1
0 -~ 4’-to 1 ~ -~1”’4 1
(‘40’ 0001
1 -o luit(“4
4.1 —m 01 ‘14
~ 1 (‘“‘4 0t~ (‘~ 01
o 1 (“4 (‘1 -~1 ~CV~ 0
~ N-’f400 (‘-1
CS1~ 1 t 01
~~—00— —~~0 ‘QOc,1 01
(‘,r~ (‘4 01
~ —dN~ ~4’— 0 0’ 4’- —~ 0 (‘-1 —~ (‘4 r-141 -~ OsII) 4’.-~~t’4 010’ (‘.1wI -40~0s4~Osr~ 01
~ t4~ 1. -14’0 rsl 0 c’i — -.,j — m-~ - - ‘ - 1
.51”’ “‘~ 0’
0’N
—r(’lc44’r-14 ‘~u ~‘0’
~— r—.(‘1 (‘4 0’
~, R~,,,~ i~ liii
4’-’ 2t-0
~t-~14 ‘-4,0.4d
4-4ilu11uIP~~14
~ :‘c5~144-’
— 44 —
i ‘-‘~0’ 01 c’4— ‘0
~4’2(-~0’ 01— 50
IN (‘1 -~
c~~(’~~(?(‘-5 4’- IN c”4 c’-~— -7
r~ -141~
(-101
0’1
r—(-
‘t’
IN01
0’ —t’4 —
~1~5
014N
,.~ (~‘~
01 0 (‘4 -7 ~— 4-,
t-’14(4
‘-4
-40)
.0
01
t,1414(4
140t-’14
0)01
1414t’-’
(~4>
‘0t(‘4
14-4
(0‘-4
‘-4t-4
0101
1414t’-’
5-, 1401.01
~0t
“4
(0
10
t
14“4 001414
5, 014’-)
-t
-7
‘04’(‘4
(0
10
t
0)‘-40$44400 4-40~
144)0)01
to
I-10)
4,4—
0)1EOto1-itoO
‘0WO4,4 -i-4to
�0
0‘—4 to
E-4‘00�00
to01
0)0
E0)~.1
0)0toWO)Xli
I1-4 44
0
01-1toEO
C~Q).04,4
0)-4.0
‘0‘7
‘0-14
4’-‘-4
010-5
‘-4 -- ‘0
t 1 01‘0
t 01‘0
t 4—
4 1 ‘001
t 1 ‘001
t r—
(‘1
0 0’ —
(‘4 0 (‘4(‘4 -14
t’l 0 (N — (‘1(‘1 -7
‘-~‘“2 ~t- t~- t-t — (‘4—
(‘20 (‘~ 01
— ‘14
0 ~,01 ‘0 (( 0 0’- ‘ ‘ 1 1 0’ —
(‘4 0 “4 - -
05400-44,,0)20,-.)O~0
~Xl-’0n~4-40rSc_)
‘00~ 4’,
E ~ >~ —So 00 - ‘v (014 ‘-— -o ~
- 0 E ‘— ,t‘-4 0) 01 - 14
44 .4’ (4 ,0 ~00 00 (0 - - 04 t~( 14t 5-( ‘.-~ 0) 14 --4 14 -o01 01 1-. 44 ‘4-4 I~— ) t ‘0 14
0 t-’ ‘4 - 01 t0( ‘-1 )S t 0
00 00 ~4 , 44 ,~4 -4‘0 14 ,-c .4 ~, ,~ -414 ‘4 0 ) ) 14 (~1 (00) 01 t 0 0 t 0 144’ ~‘ 0 4- t~ 14-~ -c c,, C,~ 0 0 (/4
‘0011-~
(0(0
0t
1~0
01
.014‘4
t,-t-
14
0t
‘4)
t0‘/4
— 45 —
Primary productivity is a measure of the natural food available forfish within a pond. The larger the fish, the more absolute amounts of food itrequires to maintain body weight and the potential for growth. When availablefood is just sufficient to maintain the fish but not allow growth, the pondhas reached its “carrying capacity” for the type, number, and size ofindividuals living within it (22). The primary productivity of the aqua—culture ponds was measured during June to October 1983 (Phase 1) by CEPIS.The overall average in the ponds was 1,645 mg”02/m
2—hr, but rather largefbuctuations occurred now and then —— at one point, for example, productivityrose from 220 to 3,345 mg—0
2/m2—hr in Q2 within just 2 days. Even go, the
average daily value of 12.6 g—02/m
2—d indicated high productivity even underbess favorable winter conditions (6).
After the harvests of Phase II, researchers at IJNA processed tilapiaby both the wet salting and smoking methods. Color, texture, and taste ofboth salted and smoked tilapia were considered good and competitive with otherlocally available products (27).
FISH MICROBIOLOCICAL ASSESSNENT
When fish are growri in wastewater, bacteria present in the watercolumn enter their digestive tract. From there it can pass into thebloodstream and end up in the various organs of the fish. However, thenumbers of bacteria in the water column must be high before the bacteria willend up in the fish muscle (which is the typically edible portion). Thenumbers and kinds of bacteria reaching the muscle depend on the immune systemof the fish, the degree to which the fish is exposed to high concentrations,and the general health of the fish at the time of excessive exposure (9,Suras).
The primary purpose of the microbiology studies in Lima was to assesswhether the fish under consideration contained microorganisms that could bepathogenic to humans. These bacteria would not typically be pathogenic tofish but they could stress the fish. Any type of bacteria can cause theimmune system of the fish to become bbocked and therefore increase the fish’svulnerability to infection by its own pathogens (9, Buras).
Aquaculture experiments jn Israel and the United States suggest thatthe numbers of bacteria in the digestive tract may often be equal to, orhigher than, the numbers in the surrounding water (10, 20). Peritoneal fluidwould typically be the next most contaminated part o~ the fish (9, Buras). InIsrael, only when fish received inoculations of 10 E. coli per fish was E.coli subsequently detected in fis~i muscle. In pond water, concentrations ofE. coli had to be higher ~han 10 /100 ml to cause muscle contamination. Onthe other hand, only 10 /mb of Salmonella or Streptococcus fecalis wasnecessary to cause muscle contamination (7). In the San Juan aquacultureponds, E. coli were present on the order of io2 — l0~/l00 ml and Salmonella onthe order of lO/ml.
In MPN tests during the early months of aquaculture, relatively highlevels of total coliforms were present in the DTC of raw tilapia from the T2
— 46 —
pond (1.8 times io~iioo ml). Fecal coli~form levels in the digestive tract ofT2 tilapia were also high (1.4 x io6/ioo ml. Total coliform and fecalcoliform levels found in the DTC of tilapia were markedly lower in ponds ofhigher water
4quality; for examp1~e, the levels in tilapia harvested from Q2were 1.1 x 10 /100 ml and 2 x 10 /100 ml, respectively. Coliform counts weresomewhathigher in the DTC than in water samples (28).
After the accidental excessive boading occurred in the Series 2ponds, total coliform and fecal coliform levels in T2 fish rose (2.2 x 10
8/iOOml in both cases). By harvest ~ime, several months later, these levels haddecreased significantly (2.5 x 10 /100 ml and 1.4 x io~iiüø ml, respectively).Similarly, total coliform and fecal coliform levels in Q2 f~sh rose after theaccidental excessive loading (1.8 x 1o8/ioo ml and 7x10~/l00 ml, respec—tively), and were reduced at harvest time (8x104/100 ml in both cases) (28).
Fecal coliforms were not recovered from most MPN tests on muscie, andtotal coliforms were present only in low concentrations—less than 50/100 ml(28). These results are compatible with those from studies conducted in theUnited States, South Africa, and Israel, all of which found levels of fecalcoliforms to be either zero or extremely bow (less than 25 per 100 g, evenwhen levels in the DTC were 10~per 100 g) (9, Buras; 20; 29).
Studies conducted in Israel showed that when fecal coliformconcentrations in muscle are very low or nonexistent, contamination by otherbacteria may be found. MPN tests for coliforms were therefore deemedinadequate as a means of indicating pathogenic contarnination in aquaculturestudies (9, Buras). For this reason, SPC tests (as well as MPN tests) wereperformed in the latter stages of the Lima aquaculture studies.
SPC procedures revealed a significant population of bacteria,inciuding enteric bacteria, in the peritoneal fluid and muscle of raw tilapiasamples from both T2 and Q2. An average of 3.1 x io2 bacteria per gram ofmuscie were found in tilapia grown in T2, and 4.5 x 102 bacteria per gram ofmuscle were recovered in those grown in Q2. In Cl, 2.3 x 1O2 bacteria pergram of muscl-e were recovered in the carp, whereas no bacteria were recovere~from muscie of the tilapia grown there (28). Pond water samples averaged 10SPC/ml (6).
Among the bacteria recovered by SPC procedures from the DTC oftilapia in T2 and Q2 were E. coli, Citrobacter freundii, Klebsiella sp.
,
Proteus vulgaris, and Enterobacter cboacae. Salmonella bacteria were isolatedfrom the DTC in some of the T2 and Q2 tilapia samples, and Streptococcusfecalis was found in the DTC of some of the T2 and Cl big belly carp samples(28).
All samplings of gilI, muscie, and the DTC of raw tilapia, carp, andprawns were negative for protozoa cysts and helminths (28).
On the basis of the numbers of bacteria found in muscie, the qualityof fish grown in the San Juan lagoons was determined to be acceptable forhuman consumption (9, Buras and Hepher). According to the international
— 47 —
standards for freshwater fish allowable for human consumptiojl, the SPC forthree of the five fish sampled should not exceed 1 times 10~/10O g and thefecal coliform count should not exceed 4/100 g (10).
The main public health concern is that in the cleaning and preparingof fish in home kitchens or restaurants, people may spread the contaminationfrom the digestive tract or peritoneal flujd to foods that can be eaten raw(inciuding fish muscle, which is often consumed raw in Peru in a marinatedsalad known as “ceviche”). For this reason, controlled fish processing andpackaging was recommended as a means of rninimizing public health risk. SPCbacteriobogy tests on tilapia from T2 indicated that smoking reduced totalbacteria levels. Surprisingly, salting did not reduce total bacteria,presumably because the salt used was contaminated (27).
In a few trials of depuration, fish were placed in clean water for 3to 7 days. However, the data from the subsequent microbiobogical studies areinconclusive. Oddly, coliform bacteria were recovered from the muscie of T2fish after depuration, but not before. No significant decrease in bacterialcontent within the DTC of the fish occurred after depuration (28). Assumingthat the depuration water was free of pathogens, the unexpected contaminationin the fish could have resulted from handling stress (9, Hepher). Accordingto another theory, the relatively high pil levels of the aquaculture pondscould have suppressed the growth of most types of bacteria (except thoseresistant to pH, such as Streptococcus fecalis) until the fish were placed infresh water (10).
(INA and ITINTEC grew tilapia in clean water tanks in which digestedanimal manure was used to fertilize the production of natural fish food(24). USM—IVITA conducted microbiobogical studies on a sampling of thepartially grown fish. Total coliform counts and overall bacterial presencewere somewhat higher in these tilapia than in those from the wastewatertreatment ponds: tot~l coliforms measured by MPN reached 2.5 x 10~/lO0 ml inthe DTC and 1.3 x lo~/ioo ml in muscie; SPC showed levels up to 4.2 x 102bacteria/ml in muscle; fecal coliforms were found in the DTC but less than20/100 ml were found in the muscle (28). As in the fish raised at San Juan,bacteria counts in the DTC were somewhat higher than those found in the waterc 01 umn.
TOXICOLOGICAL ASSESSMENT
A few samples were analyzed for trace metals and pesticides, but theresults do not indicate any accumulation of toxic substances in tilapia grownin San Juan ponds. A combined sample of six fish collected for toxicologymeasurements yielded 1,057 g of homogenized muscle tissue for analysis. Theresults of this analysis are shown in Table 14. Gas chromatographic analysisfor organochlorinated pesticides showed only one minor peak of bowconcentration (0.001 micro g/g), which was not identifiable but appearedsimilar to Aldrin and could be an isomer (6).
— 48 —
Table 14. Results of Analysis on Fish Muscie Sample (l,057g)
,
May 1984
Pesticide analysis (gualitative)
OrganophosphorusOrganochborinated
negative (<0.2 ug/g)negative (<0.2 ug/g)
Analysis Result
Bromatological analysis
Water content 80.3%Lipid content 0.4%Fixed solids 1.2%
Trace metal analysis
MercuryLeadCadi umChromium
0.3 ug/g0.26 ug/g
not detected (<0.01 ug/g)not detected (<0.1 ug/g)
Source: (6)
— 49 —
Chapter 5
~ONCLUSIONS
The principal findirig of the aquaculture studies is that fish grew inall of the ponds. However, the growth rate appeared favorable only in thefourth— and fif th—level ponds.
During the low temperature months (Phase 1), the critical standingcrop —— the weight of fish at uhich the pond can no longer support an increasein daily growth rate —— of the fourth—level ponds (Cl and C2) was 250 kg/ha.The carrying capacity —— the maximum weight of fish that the pond can sustain—— was 550 kg/ha (27).
During warmer months (Phase II), the critical standing value of thefifth—level pond (Q2) was 600 kg/ha and the carrying capacity was 1,350kg/ha. The improved values were largely due to the higher level of naturalfood produced at warmer temperatures. Also, the water quality was better(27).
Polyculture began at the end of the Phase II summer months. As watertemperatures declined from 26°C to 21°C, the daily growth rate for tilapia didnot rise as high as the rate for carp (27).
Pravns raised duririg Phase 1 exhibited a good growth rate for the lowwater temperatures, but poor harvesting conditions led to mortalities. DuringPhase II, poor water quality led to mortalities. Despite the problemsencountered, the researchers believe that the potential for prawn cultureunder more controlled conditions appears good (27).
The bacteria loads of fish harvested from aquaculture ponds wereacceptable for human consumption (in terms of number of bacteria and fecal
coliform count within the muscle portion). Improved processing would ensurethat home kitchens did not become contaminated by bacteria from the fishdigestive tract (9, 27).
The key water quality parameter for fish growth and productionappears to be ammonia. The following maximum ammonia concentrations arerecoomiended (6):
Total ammonia (NH.~ + NH4~) 2.0 mg—N/lAverage un—ionizea ammonia (NH-t) 0.5 mg—N/lShort duration NH3 diurnal peaks 2.0 mg—N/1
Dissolved oxygen did not present problems under typical operatingconditions, even with normal diurnal variations and heavy benthal deposits(6).
— 50 —
Detergent levels at San Juan did not present problems for fishculture, as the aquaculture ponds were generally maintained below 1 mg—MBAS/lof ABS detergents (6).
Fecal coliforms were effectively maintained below ~ MPN/100 ml, andtherefore no fecal coliforms were recovered from the muscie of fish (6, 9,28).
Complete protozoa and helminth removal was achieved in the primaryand secondary treatment ponds; therefore parasites were not a problem in theaquaculture ponds (6).
Good treatment pond design and operation are vital for pathogenremoval. Among the factors that should be considered are: the use of baffiedoutlet structures to prevent pathogen breakthrough on floating solids; properposition of inlet and outlet structures; and proper pond shape to reduceshort—circujting due to thermal stratification (6).
Ponds in which aquaculture is to be conducted need to be speciallydesigned to facilitate regular sludge removal and fast and effectiveharvesting by seining (27).
Pond management must consider the human element. Fish ponds need tobe adequately protected from external interference, such as people stealingfish or sabotaging the pond structure so that water quality is disturbed (6).
The fish grown in San Juan’s treated domestic wastewater did notcontain significant levels of heavy metals or pesticides. However, furtherstudy would be needed to determine the levels of toxic substances inwastewater containing industrial loads (6).
— 51 —
Chapter 6
RE~OMMENDATIONS
In March 1985, a panel of experts on fish culture and epidemiologywas convened in Lima, Peru, for 5 days to closely examine the Lima aquaculturestudies vis—â—vis the global state—of—knowledge. At the conciusion of themeeting, the panel put forth a number of recommendations, and plans are nowunder way to implement them under the UNDP Integrated Resource RecoveryProject, with financial support from the GTZ. Following are the principalpoints emphasized in the panel’s review of the Lima studies:
The Phase T and II studies at San Juan providedindicative data on water quality requirements, choice offish species, potential growth rates and yields, and publichealth aspects of sewage—based fish culture. However, toderive design standards and monitoring criteria forextension of the technique, more investigative studies arenecessary. New fish ponds are needed to enable replicableand statistically significant results, as well as todemonstrate appropriate design configurations.
Economjcg received little attention in Phases 1 and II,but studies will be crucial in setting future priorities.Culture of high value products, such as large tilapia (ca.500 g) and prawns, requires careful management and moreexpensive inputs than culture of carp and smallertilapias. Options for choice of products range from highvalue foods for direct human consumption to fish seed (forgrow—out elsewhere) and fish biomass (irrespective ofindividual size) as an animal feed ingredient.
The following economic studies should be undertaken toenable a fuller assessment of the potential of wastewater—fed aquaculture: (1) Macroeconomics — fish and fishproducts supply, demand and markets (local, national,regional, and global); (2) Microeconomics of the proposedwastewater—fed culture systems with various end products;(3) Socioeconomics of the same systems and possiblebeneficiaries, wïth consideration of possible income and/ornutritional improvement for the urban and rural poor.Socioeconomic studies are particularly important and shouldinciude product preference, markets, food preparationhabits, health status, health risks from aquaculture andpresently available alternative food items, nutritionalstatus, cost—benefit analyses, and comparisons with otherre—use options such as ~rrigated vegetable production.
— 52 —
Phases T and II provided a valuable insight into fishgrowth in wastewater lagoons, but because of the limitednurober of ponds used in the study and their design for onlywastewater treatment, further studies are needed to providebio—engineering design criteria for wastewater reuse throughaquacult ure.
A series of experimental porids designed specificallyfor aquaculture is required to permit scientific assessmentof the varjous parameters involved in the use of wastewaterin aquaculture. A scientific experiment with statisticallymeaningful data would involve a minimum of 4 treatments intriplicate — a total of 12 experimental ponds. These pondsmust be large enough to obtain meaningful data for testingin larger pilot scale/demonstration ponds but small enoughto permit an adequate number to be used for a sci~ntificallyvalid study. An experimerital pond size of 400 m is recom—mended.
A smaller number of larger pilot—scale/demonstrationponds is required to test the resuits of the experimentalstudies on a more realistic commercial scale. Data obtainedfrom these ponds would be used for an economic assessmentofthe various options of wastewater reuse in aquaculture. Theponds would also be used as a demonstration of economicallyviable wastewater reuse options. It is recommendedthat atleast 2 ponds of 2,500 m2 be constructed for this purpose.
Ponds would also be needed at the facility forservicing the experimental work.
Construction of a service reservoir is recommended toensure adequate water quality control. Also, a well shouldbe constructed on the site to provide a supply of cleanwater to g~ve flexibility j~ the quatity of water suppliedto the facility (21).
The panel of experts also provided detailed suggestions on the typesof experimental programs to be conducted using the recommended aquaculturefacility. The following are some of their recommendations: test severalstocking densities (from 0.1 to 2/m2) of monosex file tilapia and then bluetilapia; inciude several different portions (from 0 to 20 percent) of commoncarp with the optimum monosex tilapia stocking density; iricrease the size ofthe harvested fish through use of suppiemental rice bran at several portions(from 0 percent to 6 percent body weight/day); repeat the above tests fordifferent water quality levels (in ponds receiving influent equivalent tothird—level to fifth—level. treated wastewater). They further advised thatmore attention be given to measuring natural food within the ponds: thephytoplankton, zooplankton, and benthos (21).
— 53 —
They also noted that tests for Standard Plate Count and Most ProbableNumber should continue to be performed on the digestive tract, peritonealfluid, and muscie of the cultured specimens. Because only a few pathogenswere recovered from fish muscie, it was recommended that sample sizes besubstantially increased and that additional bacteria (e.g., Campylobacterj~ejuni and various vibrios) be investigated. Initially, serobogicalexaminations of fish sera would be performed (versus direct virus isolation)to investigate the presence of viruses. In addition, the panel recommendedthat fillets of processed fish be tested for the presence of Clostridiumbotuliniuxn and Staphylococci toxins (21).
- 54 —
REFERENCES
1. Arionymous. Health Aspects of Wastewater and Excreta Use inAgriculture and Aquaculture: The Report of a Review Meeting ofExperts held at Engelberg, Switzerland. Meeting Sponsored bythe World Bank and World Health Organization. Dubendorf,Switzerland: International Reference Center for Wastes Disposal,July 1985.
2. Anonymous. Impressive Yield from Sewage—Fertilised Paddy Plots.Research Highlights, Newsietter of the Central Inland FisheriesResearch Institute (CIFRI). Barrackpore, India, 1983.
3. Anonymous. Lima, Peru: Ley General de Aguas, Ministerio de Salud,1970.
4. Arthur, J. P. Notes on the Design and Operation of Waste Stabi—lization Ponds in Warm Climates of Developing Countries, UrbanDevelopment Technical Paper no. 6. Washington, D. C.: TheWorld Bank, 1983.
5. Balarin, J. D. Towards an Integrated Approach to Tilapia Farming inAfrica. Mombasa, Kenya: Baobab Farm Limited.
6. Bartone, C. R., and others. Monitoring and Maintenance of TreatedWater Quality in the San Juan Lagoons Supporting Aquaculture:Final Report of Phases 1—11. Pan Ainerican Center for SanitaryEngineering and Environmerital Sciences (CEPIS), UNDP/WorldBank/GTZ Integrated Resource Recovery Project. Lima, Peru,April 1985.
7. Buras, N., L. Duek, and S. Niv. Reactions of Fish to Microorganismsin Wastewater. Applied and Environmental Microbiology,50(4)989—95, October 1985.
8. Campos, M. Correspondence to C. Bartone Regarding Disease Incidencein Lima. Lima, Peru: Instituto de Medicina Tropical “Alexandervon Humboldt,” January 1984. Processed.
9. Cointreau, S. J., B. Hepher, and N. Buras. Unpublished Memoranda inUNDP/World Bank Integrated Resource Recovery Project FilesRegarding F’ishculture Studies at the San Juan Lagoons.Washington, D.C.: The World Bank, May 1982 to March 1985.
10. Cointreau, S. J. Unpublished Field Notes from World Bank Project—Sponsored Visits to Lima, Peru, 1982 to 1985.
11. Edwards, P., and others. A Feasibility Study of Fish/Duck IntegratedFarming at the Family Level in Central & Northeast Thailand.Asian Institute of Technology Report no. 163. Bangkok,Thailand: September 1983.
— 55 —
12. Edwards, P., and others. Compost as Fish Feed, a PracticalApplication of Detritivory for the Cultivation of Tilapia.Aguaculture. Amsterdam, Netherlands: 1983.
13. Edwards, P., and others. Re—Use of Cesspool Slurry and CelluloseAgricultural Residues for Fish Culture. Asian Institute ofTechnology Report no. 166. Bangkok, Thailand: March 1984.
14. Edwards, P. Pond Fish Can Thrive on Treated Human Waste. FishFarming International, April 1985.
15. Edwards, P. Aquaculture: A Component of Low Cost SanitationTechnology. World Bank Technical Paper no. 36, Washington,D.C., 1985.
16. Engineering—Science. Desague Plan Maestro y Primera Etapa delPrograma de Ampliaciones. Empresa de Saneamiento de Lima, Peru,November 1981.
17. Feachem, F. G., and-others. Sanitation and Disease: Health Aspectsof Excreta and Wastewater Management. World Bank Studies inWater Supply and Sanitation——3. New York: John Wiley & Sons,1983.
18. Furedy, C., and D. Ghosh. Resource—Conserving Traditions and WasteDisposal: The Carbage Farms and Sewage—Fed Fisheries ofCalcutta. Calcutta, India: Department of Fisheries, Governmentof West Bengal, 1984.
19. Goidstein, S. M. Rwanda: Aquaculture. AID Resources Report.Washington, D.C.: U.S. Agency for International Development,1984.
20. Hejkal, T. W., and others. Bacteriological, Virological and ChemicalEvaluation of a Wastewater—Aquaculture System. Water Resources,vol. 17, Great Britain, 1983.
21. Hepher, B., N. Buras, R. Pullin, P. Edwards, D. Ghosh, and H.Schlotfeldt. Review of Treated Wastewater—Baged Fish CultureStudies at the San Juan Lagoons in Lima, Peru. Expert PanelMeeting Sponsored by the German Agency for Technical Cooperation(CTZ) and the World Bank, Lima, Peru, March 1983.
22. Hepher, B., and Y. Pruginin. Commercial Fish Farming: With SpecialReference to Fish Culture in Israel. New York: John Wiley &Sons, 1981.
23. Lloyd, B., Lagoon Treatment of Sewage and the Health Risks Associatedwith the Survival of Enteric Pathogens, with ParticularReference to Coastal Peru. Department of Microbiology,University of Surrey, Great Britain, December 1982.
— 56 —
24. Luna, T., and M. Carrasco. Evaluacion del Bioabono en la Fertili—zacion de Estanques para La Crianza de Peces. Lima, Peru:Universidad Nacional Agraria ((INA) and Instituto deInvestigaciones Tecnologicas Industriales y de Normas Tecnicas(ITINTEC), July 1984.
25. Mann, R. Exotic Species in Aquaculture: An Overview of When, Whyand How. Woods Hole, Mass.: Woods Hole OceanographicInstitution, n.d.
26. Mock, C.R. Some Sources of Information on Shrimp Farming Operationsand Research Organizations. Galveston, Tex.: U.S. Department ofCommerce, National Oceanic and Atmospheric Administration,Galveston, n.d.
27. Moscoso, J., H. Nava, and others. Research, Development and Demon—stration Efforts on Aquaculture in Lima. Universidad NacionalAgraria ((INA), (INDP/World Bank Integrated Resource RecoveryProject, FinaL Report on Phase II Fish and Shrimp Culture andFood Processing Studies, August 1984.
28. Noe, N., and others. Research, Development and DemonstrationEfforts on Aquaculture in Lima. Centro de InvestigaticionInstituto Veterinario de Tnvestigaciones Tropicales y de Altura(IVITA), UNDP/World Bank Integrated Resource Recovery Project,Final Report on Phase II Bacteria and Parasite Studies, June1984.
29. Nupen, E. M. Possible Health Hazards in Fish Farming Using Sewage.Paper Presented at IWSA/CSIR Seminar, CSIR, Pretoria, South
Africa, September 1983.
30. Nupen, E. M., and E. Sandbank. Health Aspects of Fish Aquaculture inSewage—Polluted Waters. Source unknown.
31. Reed, S. C., and R. K. Bastian. Aquaculture Systems for WastewaterTreatment: An Engineering Assessment, U.S. EnvirorunentalProtection Agency Publication 430/9—80—007. Washington, D. C.:June 1980.
32. Reed, S. C., and others. Engineers Assess Aquaculture Systems forWastewater Treatment. Civil Engineering Journal —— ASCE, NewYork, July 1981.
33. Shuval, H. T., and others. Health Effects of Wastewater Irrigationand Their Control in Developing Countries. Draft Report,IJNDP/World Bank Integrated Resource Recovery Project (WasteRecycling —— GLO/80/004, GLO/84/007). Washington, D.C.: April1985.
— 57 —
34. TARAL. Estudio de Factibilidad del Proyecto de Reuso de AguasServidas para Irrigacion de Zonas Aridas al Sur de Lima:Informe Final. TAHAL Consulting Engineers, Ltd., PublicacionNo. 04/85/21, June, 1985.
35. (lnpublished Health Statistics from 1970 to 1980. Miriisterio deSalud, Lima, Peru, May 1982.
36. Vinces, A. Informe Que Presenta Al Directorio de Senapa Sobre ElPrograma de Investigaciones de San Juan. Lima, Peru: 1983.Processed.
37. Yanez, F., and others. Evaluation of the San Juan StabilizationPonds. Lima Peru: Pan American Center for Sanitary Engineeringand Environmental Sciences (CEPIS), April 1980.
38. Yanez, F., and others. Manual de Metodos Experimentales, Evaluationde Lagunas de Estabilizacion. Lima, Peru: Centro Panamericande Ingenieria Sanitaria y Ciencias del Ambiente (CEPIS), April1982.
39. Yanez, F. Indicator and Pathogen Organism Die—Off in Ponds andDesign under Tropical Conditions. Paper presented at 56thAnnual Conference of the Water Pollution Control Federation,Atlanta, Georgia, 2—6 October 1983.
40. Zandstra, 1., ed. Reclamation of Nutrients, Water and Energy fromWastes: A Review of Selected IRDC—Supported Research. DraftReport of the International Research and Development Center(IDRC), Canada, n.d. Processed.
