utilizing biosolids on agricultural land - michigan …warncke/e2781 utilizing biosolids on...u.s....

Utilizing Biosolidson

Agricultural Land

E x t e n s i o n B u l l e t i n E - 2 7 8 1 • N e w

D e c e m b e r 2 0 0 1

ByLee W. Jacobs and Deliana S. McCrearyDepartment of Crop and Soil Sciences

Michigan State University

MICHIGAN STATEU N I V E R S I T Y

EXTENSION

2

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Biosolids Management Options in Michigan . . . . 4

Landfilled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Surface disposal . . . . . . . . . . . . . . . . . . . . . . . . . 5

Incineration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Land application . . . . . . . . . . . . . . . . . . . . . . . . . 5

Other beneficial uses. . . . . . . . . . . . . . . . . . . . . . 6

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Process of Biosolids Production . . . . . . . . . . . . . . 7

Potential Concerns with Land Application . . . . . 8

Parasites and pathogens . . . . . . . . . . . . . . . . . . . 8

Heavy metals and trace elements. . . . . . . . . . . . . 8

Organic contaminants. . . . . . . . . . . . . . . . . . . . 10

Salts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Radioactive materials . . . . . . . . . . . . . . . . . . . . 11

Public acceptability . . . . . . . . . . . . . . . . . . . . . . 11

Regulations on Utilizing Biosolids . . . . . . . . . . . 12

Part 503 risk assessment . . . . . . . . . . . . . . . . . . 12

Pollutant limits . . . . . . . . . . . . . . . . . . . . . . . . . 14

Lifetime biosolids applications . . . . . . . . . . . . . 15

Pathogen reduction. . . . . . . . . . . . . . . . . . . . . . 15

Vector attraction reduction . . . . . . . . . . . . . . . . 17

Organic pollutants . . . . . . . . . . . . . . . . . . . . . . 17

Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Wildlife and endangered species . . . . . . . . . . . . 18

Monitoring frequency and state rule prohibition . . . . . . . . . . . . . . . . . . . . 18

Additional regulatory restrictions required by Part 24 Rules . . . . . . . . . . . . . . . . . 19

Biosolids Quality. . . . . . . . . . . . . . . . . . . . . . . . . 20

Nutrient Value of Biosolids. . . . . . . . . . . . . . . . . 24

Nitrogen in biosolids . . . . . . . . . . . . . . . . . . . . 24

Phosphorus, potassium and other

plant nutrients in biosolids . . . . . . . . . . . . . . . . 25

Establishing and Managing Successful Biosolids Land Application Programs . . . . . . . . 26

Site selection and land availability. . . . . . . . . . . 27

Determining agronomic rates for biosolids applications . . . . . . . . . . . . . . . . . 28

Biosolids application. . . . . . . . . . . . . . . . . . . . . 29

Monitoring program . . . . . . . . . . . . . . . . . . . . . 30

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table of Contents

3

Biosolids are solid, semisolid and liquid residuesgenerated during the treatment of sanitarysewage, or domestic sewage, in treatment

works treating domestic sewage (TWTDS). The termwas introduced by the wastewater treatment industryin 1991 to describe the residuals or solids createdduring the biological treatment of wastewater (hence“bio-solids”). The U.S. Environmental ProtectionAgency (USEPA) recently adopted the name“biosolids” to differentiate high quality treated sewagesludge from raw sewage sludge and from sewagesludge containing large amounts of pollutants.Therefore, sewage sludges must be processed to meetUSEPA standards for beneficial reuse before they canbe called biosolids. The Michigan Department ofEnvironmental Quality (MDEQ) has also adopted thisterm for rules made effective in November 1999.

Like animal manure, biosolids are part of the naturalcycle of life. They contain inorganic and organiccompounds removed during wastewater treatment.The beneficial use of biosolids for land applicationallows for the nutrient content and soil amendmentproperties of these residuals to be usedadvantageously for sustained crop production. Fordecades, sewage sludge has been used with greatsuccess on agricultural lands throughout the world.Land application has been increasingly regulated toprotect human health and the environment fromvarious constituents that can be found in biosolids,such as bacteria, viruses and other pathogens (i.e.,disease-causing organisms), metals (e.g., cadmiumand lead), toxic organic chemicals (e.g., PCBs) andnutrients (the most important being nitrogen and

phosphorus). Forty years of research anddemonstration projects on applying biosolids to landhave provided a good scientific basis for the safe useand return of biosolids in our environment.Collectively, this research leads to the conclusion thatagronomic use of high quality biosolids is sustainableand very safe (USEPA, 1994c). These scientific studieshave helped to shape the U.S. federal regulatorystance for biosolids (Rubin, 1997).

As shown in Figure 1, approximately 36 percent ofU.S. sewage sludge was beneficially applied to land,48 percent was landfilled or surface disposed, and 16percent was incinerated in 1988 (USEPA, 1992a). By1998, only 17 percent of sludge was being disposedof in landfills or sludge-only disposal sites, andbeneficial use increased from 36 to 60 percent(USEPA, 1999b). Because of reduced availability ofspace for landfilling and surface disposal, incinerationincreased slightly from 16 to 22 percent.

New uses of biosolids have been developed in recentyears, and the science behind established practiceshas greatly improved. Now more and morecommunities are turning to land application. Forexample, over 55 and 90 percent of all biosolidsproduced in Ohio and Maryland, respectively, areutilized on land (USEPA, 1992a). In Michigan,approximately 61,800 dry tons of biosolids wereapplied to land in 1990; 81,500 dry tons were landapplied in 1997, and 83,100 dry tons in 2000(personal communication with MDEQ).

Introduction

4

I n t ro d u c t i o n

Landfill/surfacedisposal (48%)

Incineration(16%)

Beneficial use(36%)

1988

Landfill/surfacedisposal (17%)

Incineration(22%)

Beneficial use(60%)

1998

17%

22%

60%16%

36%

48%

Figure 1. How management of biosolids/sewage sludge changed from 1988 to 1998 (adapted from USEPA, 1992a and 1999b).

Biosolids Management Optionsin Michigan

Whether biosolids can be used as afertilizer or soil amendment or simplydisposed of as sewage sludges depends

on their stability, degree of pathogen treatment,pollutant concentrations, extent and cost ofprocessing, local geography, climate and land use,public acceptance and regulatory constraint.Management options available for biosolids/sewagesludge fall into four categories:

• Landfilled.• Surface disposal.• Incineration.• Land application and other beneficial uses.

LandfilledLandfill disposal offers the simplest solution tobiosolids handling by concentrating the material in asingle location. When a landfill is properlyconstructed and maintained, the risk of release ofpollutants and pathogens into the environment frombiosolids is minimal. Economically, the cost comparesfavorably with other options. Landfill disposal is notwithout problems, however. Identifying landfill sitesand going through the permitting and approvalprocess are not easy, and some areas have landfillshortages. Buried organic wastes undergo anaerobicdecomposition that produces methane gas. In

5

B io so l i d s Manage men t O p t i on s i n M i c h i g a n

addition, chemicals and nutrients can move to localgroundwater when older landfills do not havesynthetic liners or a liner in a newer landfill developsa leak. Moreover, the potential benefits of organicmatter and plant nutrient recycling are lost.

Surface disposalIn surface disposal, biosolids are placed on an area ofland (site) for final disposal. These areas may bemonofills, lagoons, waste piles, surfaceimpoundments or dedicated disposal sites. Surfacedisposal sites do not exist in Michigan and are notlikely to be approved in the future, so this method isnot really a biosolids management option here.

IncinerationIncineration is the burning of biosolids at hightemperatures in an enclosed device. It reduces thebiosolids volume, kills pathogens and destroys mostorganic chemicals, but it requires energy and safedisposal of the resulting ash. The remaining ash is astable, inorganic material containing 10 to 20 percentof the original solids. A problem with this method isthat it does not destroy trace elements but ratherconcentrates them in the ash — levels in ash are fiveto 10 times the original levels. In addition, the ashstill requires disposal in landfills. Incineration alsoproduces carbon dioxide, a greenhouse gas, whoserelease to the atmosphere has been implicated inpossible global warming, and the potential benefits oforganic matter and plant nutrient recycling are lost.This option is one of the most expensive methods fordealing with biosolids because it requiressophisticated systems to remove fine particulatematter (fly ash) and volatile pollutants from stackgases. The 40 Code of Federal Regulations (CFR), Part503, titled “Standards for the Use and Disposal ofSewage Sludge” (or Part 503) risk assessment,

indicates that incineration clearly carries the greatesthealth risk because of the release of volatile traceelements into the atmosphere.

Land applicationLand application is the application of biosolids toland, either to condition the soil or to fertilize cropsor other vegetation, or both. This method includesapplication to agricultural land and forestland,disturbed land for reclamation, conservation land orrecreational land, and dedicated beneficial use sites.Land application is usually less expensive thanalternative methods of biosolids management.

Applying liquid biosolids from the West Bay County TWTDSto cropland by injection into the soil.

The application of organic matter from biosolids canimprove the physical, chemical and biologicalproperties of the soil. Organic matter can increasewater infiltration and reduce soil erosion, increasewater-holding capacity, reduce soil compaction andincrease soil granulation, increase the ability of soil orsurface material to retain nutrients, provide nutrientsfor plant growth, and provide food and energy forbeneficial soil microorganisms. All of these beneficial

6

B io so l i d s Manage men t O p t i on s i n M i c h i g a n

properties make biosolids a good choice forhomeowners, landscapers, farmers and foresters. Inaddition, farmers can benefit from biosolidsapplication by reducing their fertilizer cost.

Agricultural use is subject to great variability overtime, however, depending on weather conditions andcrop type. Scheduling biosolids transport andapplication that are compatible with agriculturalplanting, harvesting and possible adverse climaticconditions requires careful management. When landis not available because of crop growth or because thesoil is frozen or wet, some backup contingencies areneeded, such as storage or an alternative managementoption such as landfilling or incineration.

One type of biosolids that is becoming more commonrecently is dried and/or pelletized biosolids. Becauseproducing biosolids in this form is complex andexpensive, dried biosolids are often blended withother materials and marketed as an organic-basedfertilizer with balanced nutrient levels. Alkalinestabilization has been used to also produce a nearlyodorless and granular product for use as an organicsoil conditioner and fertilizer. It can also substitute foragricultural lime.

Other beneficial usesMethane gas is generated during the anaerobicdigestion process and has considerable value forheating and electricity. Thermal conversion of sludgesto liquid fuel has been proven at a pilot-scale level,where studies have shown that 50 percent of theenergy in sludges can be recovered as a liquid oil thatis storable and transportable. Sludge ash fromincineration has been utilized in construction materialand shown to have little environmental risk.

Brown and Chaney (2000) and Chaney et al. (2001)recently summarized how biosolids and other by-products can be combined to make “tailor-made”biosolid mixtures for reclaiming disturbed lands,metal-contaminated soils, and urban and brownfieldsites. These types of remediations involve analteration of soil chemistry, particularly the adsorptionof heavy metals by minerals present in biosolids andthe decreased availability of these metals to plants. Inaddition, the organic matter from biosolids provides asubstrate for soil microbial communities in thesesurface materials, which contributes to establishingnutrient cycling for plant growth.

SummaryMichigan communities have three options formanaging their biosolids — landfilling, incineration(with landfilling the ash) or beneficial use. Comparingthe advantages and disadvantages of eachmanagement option suggests that land application islikely to remain a major option in the future,particularly for small plants (< 1 mgd, or milliongallons per day), which are generally close toapplication sites. Land application returns nutrientsand organic matter to the soil where they cancontribute to sustaining crop production. The need toreturn biosolids safely back to the environment andthe cost and problems associated with other optionssuggest that land application has become animportant management option for biosolids.

7

Biosolids are produced during the treatment ofdomestic sewage, or wastewater. Variousbiological, chemical and physical treatment

processes are used primarily to remove suspendedsolids, reduce and remove organic matter from thewastewater (decomposable organic matter can causeoxygen deficiency in the surface waters that receivetreated effluent), reduce and disinfect the pathogens(disease-causing organisms) present in wastewater,and reduce the nutrient content of the wastewaterbefore discharge. The residuals (solids) that are leftbehind in the TWTDS make up what is calledbiosolids. This process is schematically shown inFigure 2.

These residuals, or biosolids, will be further treated inthe TWTDS by additional biological, chemical,physical and thermal processes to further reducepathogen levels, reduce and stabilize thebiodegradable solids, and reduce the amount of waterrelative to the amount of solids (i.e., dewatering ordrying). Table 1 lists several types of treatmentprocesses that may be used for biosolids, the effecteach treatment has on biosolids and how thattreatment may affect the application of biosolids toland.

Process of Biosolids Production

BiologicalTreatmentProcess

Organic,Inorganic

IncomingWastewater

Screening

Rock,Grit,

Plastic,Etc.

EffluentTo Stream

PrimaryClarifier

SecondaryClarifier

Digester

Sludge

Gas

Sludge

Recycled Water(Supernatant)

BiosolidsTo Land

Application

Secondary

Figure 2. Basic wastewater treatment processes typically used by TWTDS (provided by MDEQ).

8

Plant nutrients and organic matter are useful toplants and soils, but some of the metals andother constituents that may be present in

biosolids are potentially harmful if not managedcorrectly. Concerns include parasites and pathogens,heavy metals and non-essential trace elements,organic contaminants, salts and radioactive materials.Public acceptability is another important issue.

Parasites and pathogensEven though biosolids must undergo a pathogenreduction treatment before being applied to land,health hazards associated with pathogens are still avalid concern. Protozoa, bacteria, viruses and parasiticworms may be present in biosolids. They have thepotential for causing a health hazard if they are notmanaged correctly. Some of these pathogens will dieas soon as biosolids are applied to the soil (e.g.,Salmonella spp.), but some of them can persist longerin the soil (e.g., Mycobacterium spp.). Once in the soil,however, these pathogens eventually will die offbecause of competition by well established soilmicrobial populations and the absence of their hostorganism. Table 2 lists some pathogens that can befound in untreated sewage sludges and the humandiseases they cause.

Heavy metals and trace elementsDepending on the concentration in the soils, someheavy metals can be toxic to plant species, and somepotentially toxic elements may occur at increasedlevels in the food chain. Therefore, the two concernsregarding trace element additions to soils are that ametal/trace element might (1) become toxic to cropsand/or (2) become sufficiently concentrated in anedible crop to have harmful effects on an animal orhuman that consumes that crop.

The trace elements (also referred to as pollutants) inbiosolids that are of greatest concern are arsenic,cadmium, copper, mercury, molybdenum, nickel,selenium and zinc. Lead is of somewhat lesser concernbecause of insolubility and lower bioavailability, unlessit’s directly ingested. Other metals normally present inbiosolids are manganese, iron, aluminum andchromium, as well as a few others less frequentlyencountered. Except for cadmium, these elements arenot usually taken up by plants in amounts harmful tohuman consumers. In fact, many of these elements areessential nutrients for plant and animal health. Thesemetals pose relatively little hazard to crop productionor plant accumulation, because all of them either havelow solubility in well aerated soil where field crops aretypically grown (i.e, pH 6.0 to 7.5) or are present inbiosolids in such small quantities that their addition tosoils will be negligible. In addition, certaincomponents in biosolids (such as ferric hydrousoxides, organic matter and phosphate) can bindpollutants to the biosolids, making them lessbiologically available to plants, animals and humans(Chaney and Ryan, 1993).

Potential Concernswith Land Application

9

Po t en t i a l Conce r n s w i th L a nd App l i c a t i on

Treatment processes Effect of process Effect of process when utilizing and definition on biosolids biosolids for land application

Thickening: Low-force separation Increases solids content by Lowers transportation costs.of water and solids by gravity, removing water. flotation or centrifugation.

Digestion (aerobic /anaerobic): Reduces the biodegradable Reduces biosolids quantity and Biological stabilization through content (stabilization) by lowers transportation costs.conversion of organic matter to conversion to soluble materials Reduces potential odor and carbon dioxide, water and methane. and gas. Reduces pathogen vector attraction during

levels and odor. application.

Alkaline stabilization: Stabilization Raises pH. Temporarily Reduces the nitrogen value of through the addition of alkaline decreases biological activity. biosolids. Lime-stabilized materials, such as hydrated lime. Reduces pathogen levels and biosolids can have liming value

controls putrescibility and odor. and substitute for ag lime.

Conditioning: Processes that cause Improves sludges’ dewatering Treating biosolids with polymers biosolids to coagulate to aid in the characteristic. May increase may require special operational separation of water. dry solids mass and improve considerations at application sites.

stabilization.

Dewatering: High-force separation Increases solids concentration May reduce nutrient value of water and solids. Methods to 15 to 45 percent. Lowers and land requirements.include vacuum filters, centrifuges, nitrogen and potassium Lowers transportation costs.filter and belt presses, etc. concentrations. Improves ease

of handling.

Composting: Aerobic, thermophilic, Lowers biological activity, Material has excellent soil biological stabilization in a windrow, destroys pathogens and conditioning properties. Contains aerated static pile or vessel. converts sludge to humuslike less plant-available nitrogen

material. than other types of biosolids. Increases transportation costs.

Heat drying: Use of heat to kill Disinfects sludges, destroys Greatly reduces biosolids volume. pathogens and eliminate most of the most pathogens, and lowers May reduce the nitrogen value of water content. odor and biological activity. biosolids.

Table 1. Biosolids treatment processes, effect on biosolids and effect on land application practices (partially adapted from USEPA, 1995a).

10


Organism Disease/symptoms

ProtozoaEntamoeba histolytica Acute enteritisBalantidium coli Diarrhea and dysentery

BacteriaSalmonella spp. Salmonellosis (food poisoning), typhoidShigella spp. Bacillary dysenteryVibrio cholerae CholeraEscherichia coli Gastroenteritis

VirusesHepatitis A virus Infectious hepatitisRotaviruses Acute gastroenteritis with severe diarrhea

Helminth (parasites)Ascaris lumbricoides (roundworm) Digestive and nutritional disturbanceTrichuris trichiura (whipworm) Abdominal pain, anemia, diarrhea, etc.Taenia saginata (tapeworm) Insomnia, anorexia, nervousness, etc.

Table 2. Some principal pathogens of concern usually found in domestic sewage and sewage sludge (adapted fromUSEPA, 1999a).

Organic contaminantsAlong with beneficial organic matter, biosolids alsomay contain organic chemical contaminants. Thoughvarious types of organic contaminants may find theirway into the sewer system from consumer orindustrial use, many of these organics will be brokendown or decomposed during wastewater treatment.Those organics that do not decompose will likely bestrongly adsorbed onto the organic matter particlespresent in biosolids. When biosolids are applied toland, most of these organic chemicals will bedecomposed in soil by soil microorganisms.Nevertheless, a community or sanitary districtconsidering biosolids application to the land shouldbe aware of these potentially harmful organiccontaminants.

SaltsVarious kinds of salts that can be present in biosolidscan be deleterious to seed germination or to growth ofyoung plants if high concentrations of saltsaccumulate in the rooting zone of soils. Soluble saltsare not expected to be a problem with agronomicrates of biosolids, however, particularly in humidregions such as Michigan, where leaching by rainfallwill remove excess salts from the root zones.Nevertheless, with high application rates of biosolids(e.g., use for reclamation of disturbed lands) or whereindustries are contributing high-salt discharges to thesewer system, soluble salt additions by biosolidsapplication should not be overlooked.

11


Radioactive materialsRadionuclides can become a part of wastewatertreatment plant influent in various ways. They maycome from industrial and medical facilities thatdischarge allowable concentrations of radioactivematerials to the sanitary sewer system, or they maycome from natural sources such as groundwater andstorm water entering the TWTDS that came intocontact with geologic deposits containing naturallyoccurring radioisotopes. Of special concern is thatradionuclides can become concentrated in biosolidsduring the treatment process and further concentratedas biosolids are dried or burned. Table 3 lists naturallyoccurring radionuclides expected to be detectable inbiosolids or ash, the type of radiation they produceand their half-life (half-life is the time required for theradioactive material to lose one-half of its activity).

Over the years, there have been 13 reports of elevatedreadings of alpha, beta and gamma radiation inbiosolids at municipal TWTDS. In every instance,radiation exposures were so low that regulatoryauthorities considered them to pose no threat to thehealth and safety of the public or the plant workers.

Radionuclide Type of radiation Half-life

Potassium 40 gamma 1.4 billion yearsRubidium 87 beta 52 billion yearsStrontium 90 beta 28 billion yearsCesium 137 beta, gamma 30 yearsRadon 222 alpha 4 daysRadium 226 alpha 1,617 yearsRadium 228 beta 7 yearsThorium 222 alpha 14 billion yearsUranium 238 alpha 4.5 billion years

In most of the cases where elevated radiation wasdetected, the discharges were within establishedNuclear Regulatory Commission limits. Therefore, theEPA found that radioactive contaminants did notproduce a significant or harmful dose when biosolidsare used for land application (WEF/USEPA, 1997).

Public acceptabilityOdor and aesthetics are two concerns quite normallyexpressed by most citizens if a new biosolidsapplication site is to be located near where they live.Those living downwind of a storage lagoon orspreading areas are most likely to complain of odors,and some people find the appearance of surfaced-applied biosolids visually displeasing. These problemscan be managed but must be anticipated and plannedfor in conducting educational programs.

Citizens are also concerned with the health aspect ofland application programs. In addition, some concernhas been expressed about the possibility that land-applied biosolids might damage crops, livestock orthe land itself, resulting in possible financial loss tothe farmer or his mortgage lender. Concerns have also

Table 3. Radionuclides, the types of radiation they produce and their half-lives (WEF-USEPA, 1997).

12


been expressed about the possibility of a future lossthat might occur if new discoveries were to show anunanticipated hazard from previous biosolidsapplications. Though there can be no guarantees,experience with agronomic use of biosolids has beenvery reassuring regarding these concerns, and recent

federal and state regulations/rules provide direction toensure this practice is done safely. Where biosolidshave been applied in accordance with regulations,problems that have occurred are rare and aregenerally related to inadequate field management orpoor biosolids quality.

Regulations on Utilizing Biosolids

In 1993, the USEPA promulgated the federalregulation for the use and disposal of biosolids toprotect public health and the environment from

any reasonably anticipated adverse effects of certainpollutants that could be present in biosolids. Thisrule, referred to as the 40 CFR (Code of FederalRegulations), Part 503, is based on the results ofextensive research and experience and acomprehensive multipathway-multimedia riskassessment. Part 503 establishes numerical standards,management practices, operational standards andmonitoring, and record-keeping and reportingrequirements for all of the common practices in theuse and disposal of biosolids.

Federal regulations require that state regulations be atleast as stringent as Part 503. In this case, MichiganPart 24, “Land Application of Biosolids Rules” (Part24 Rules) addresses only that portion of Part 503dealing with land application, not incineration orsurface disposal (landfilling is regulated under solidwaste regulations). Part 503 does not replace anyexisting state regulations; rather, it establishes aminimum national standard for the use or disposal ofbiosolids. States have the option to be more restrictivethan the minimum standards or to administer themdifferently than the federal regulation, but states mustimplement their regulations to meet the minimum

federal standards. Biosolids applied to the land mustmeet risk-based pollutant limits specified in Part 503,which include pollutant concentration limits (PCL)plus pathogen and vector attraction reductionrequirements. Therefore, when biosolids are appliedto land according to Part 503, built-in safety factorsprotect against human exposure to pathogens andchemical pollutants and impacts on the environment.

Part 503 risk assessmentThe biosolids risk assessment process began in 1982and involved selecting representative pathways bywhich humans, animals and plants could becomeexposed to pollutants of concern that may be presentin biosolids. Data on exposures associated with eachpathway were combined with data on allowable dosesof a pollutant to develop a limit for each pollutantthat would be an acceptable risk. This risk assessmentprocess significantly improved the basis forcumulative metal (and other pollutants) loadings forbiosolids applications to agricultural soils.

Previously, researchers had suggested limits for fivemetals that were based on their potential for planttoxicity and uptake into the food chain. Themultipathway risk assessment evaluated these fivemetals plus additional pollutants for potential impacts

13

Regu l a t i on s on U t i l i z i ng B i o so l i d s

on other exposed individuals via many routes ofexposure. Thus, the scientific basis for establishingcumulative loadings for individual pollutants wasgreatly improved when the risk assessment processwas proposed, scientifically critiqued, and then used

to establish PCLs and ceiling concentration limits(CCL) for the Part 503 Regulations. Exposurepathways used in the Part 503 risk assessment forland application of biosolids are listed and shown inTable 4.

Pathway Description of the highly exposed individual

1. Biosolids ➔ Soil ➔ Plant ➔ Human Human (except home gardener) lifetime ingestion of plantsgrown in biosolids-amended soil

2. Biosolids ➔ Soil ➔ Plant ➔ Human Human (home gardener) lifetime ingestion of plants grownin biosolids-amended soil

3. Biosolids ➔ Human Human (child) ingesting biosolids

4. Biosolids ➔ Soil ➔ Plant ➔ Animal ➔ Human lifetime ingestion of animal products (animals raisedHuman on forages grown on biosolids-amended soil)

5. Biosolids ➔ Soil ➔ Animal ➔ Human Human lifetime ingestion of animal products (animals ingestbiosolids directly)

6. Biosolids ➔ Soil ➔ Plant ➔ Animal Animal lifetime ingestion of plants grown on biosolids-amended soil

7. Biosolids ➔ Soil ➔ Animal Animal lifetime ingestion of biosolids

8. Biosolids ➔ Soil ➔ Plant Plant toxicity due to taking up biosolids pollutants whengrown in biosolids-amended soil

9. Biosolids ➔ Soil ➔ Soil Biota Soil organism ingesting biosolids/soil mixture

10. Biosolids ➔ Soil ➔ Soil Biota ➔ Predator of soil organisms that have been exposed toSoil Biota Predator biosolids-amended soils

11. Biosolids ➔ Soil ➔ Airborne Dust ➔ Adult human lifetime inhalation of dust particles (e.g., Human tractor driver tilling a field)

12. Biosolids ➔ Soil ➔ Surface Water ➔ Human lifetime drinking surface water and ingesting fishHuman containing pollutants in biosolids

13. Biosolids ➔ Soil ➔ Air ➔ Human Human lifetime inhalation of pollutants in biosolids thatvolatilized into the air

14. Biosolids ➔ Soil ➔ Ground Water ➔ Human lifetime drinking well water containing pollutantsHuman from biosolids that leached from soil to groundwater

Table 4. Exposure pathways used in the risk assessment process for land application of biosolids (USEPA, 1995b).

14


Concentration limitsa Loading ratesa

(mg/kg or ppm) (kg/ha) Pollutant

CCL PCL CPLR APLR(for EQ and PC (for CPLR (for APLR

biosolids) biosolids) biosolids and a365-day period)

Arsenic (As) 75 41 41 2.0Cadmium (Cd) 85 39 39 1.9Chromium (Cr)b — — — —Copper (Cu) 4,300 1,500 1,500 75Lead (Pb) 840 300 300 15Mercury (Hg) 57 17 17 0.85Molybdenum (Mo)c 75 — — —Nickel (Ni) 420 420 420 21Selenium (Se)b 100 100 100 5.0Zinc (Zn) 7,500 2,800 2,800 140

Applies to: All biosolids Bulk biosolids Bulk biosolids Baggedthat are land and bagged biosolidsd

applied biosolidsd

From 40 CRF Part 503: Table 1, Table 3, Table 2, Table 4, Part 503.13 Part 503.13 Part 503.13 Part 503.13

Pollutant limitsThe first parameter in determining biosolids quality isthe concentration of pollutants in biosolids. Somebiosolids contain negligible levels of pollutants; otherscontain higher levels. To ensure that human healthand the environment are protected while still allowingthe land application of biosolids, Part 503 provides

four sets of pollutant limits: ceiling concentrationlimits, pollutant concentration limits, cumulativepollutant loading rates and annual pollutant loadingrates (see Table 5).

Ceiling Concentration Limits (CCL) are maximumconcentrations of each pollutant allowed in land-applied biosolids. Biosolids that have one or more

a Dry-weight basis; mg/kg = milligrams per kilogram; ppm = parts per million; kg/ha = kilograms per hectare.b CCL and PCL for chromium were deleted from Table 1 and 3 and PCL for selenium was increased from 36 ppm to 100 ppm by

amendments to Part 503 Rule, effective October 25, 1995. c The PCL, CPLR and APLR for molybdenum were deleted from Part 503 Rule, effective February 19, 1994. The EPA will consider

establishing these limits at a later date.d Bagged biosolids are sold or given away in a bag or other container.

Table 5. Pollutant limits and loading rates for land-applied biosolids (adapted from USEPA, 1994b, and MDEQ, 1999).

15


pollutant concentrations exceeding the CCLs cannotbe land applied and must be used or disposed of insome other way.

Pollutant Concentration Limits (PCL) are the highestconcentrations of pollutants that biosolids maycontain without cumulative pollutant additionsneeding to be tracked (i.e., calculation of CPLRs is notrequired). The PCLs are also used as quality standardsfor “exceptional quality” biosolids and “pollutantconcentration” biosolids, discussed later in thisbulletin. Pollutant concentration limits are monthlyaverage values in milligrams per kilogram on a dry-weight basis.

Cumulative Pollutant Loading Rate (CPLR) is themaximum amount of pollutant that can be applied toa site in its lifetime by all bulk biosolids applicationswhen one or more PCLs are exceeded but all pollutantconcentrations are less than the CCLs. No additionalbiosolids that contain a pollutant higher than its PCLcan be applied to a site after the maximum CPLR isreached at that site for any one of the regulatedpollutants. Only biosolids that meet the morestringent PCL may be applied to a site once any CPLRis reached at that site.

Annual Pollutant Loading Rate (APLR) is themaximum amount of a pollutant that can be appliedto a unit area of land during a 365-day period. Thisterm describes pollutant limits allowed for biosolidsthat are given away or sold in a bag or other containerfor application to the land.

Lifetime biosolids applicationsOver the long term (i.e., lifetime), total biosolidsadditions to a site can be limited by a CPLR. UnderPart 503 Regulations and state Part 24 Rules, if thePCLs found in Table 5 are not exceeded, nomaximum pollutant loading limits are used. If the

PCL is exceeded for any of the regulated elements andno CCLs are exceeded, then the CPLRs must befollowed and not exceeded. If the cumulative additionsfor any of the pollutants reaches its CPLR after years ofbiosolids applications, then biosolids applicationsmust be discontinued except for biosolids withpollutant concentrations less than the PCLs.

Pathogen reductionThe second parameter in determining biosolidsquality is the presence or absence of pathogens suchas bacteria, protozoa, viruses and parasitic worms.Pathogens can cause a public health hazard if theycome into contact with crops grown for direct humanconsumption, are transported away from the site byvectors such as rodents, birds, and insects, or arecontained in runoff to surface water from applicationsites. Therefore, Part 503 and state Part 24 Rulesspecify pathogen and vector attraction reductionrequirements that must be met when biosolids areapplied to land. Based on the degree or amount ofpathogen reduction, biosolids are categorized as ClassA or Class B.

Some Michigan communities are planning to produce Class Abiosolids, typically a dry material applied to the soil surface.

16


when applied according to specified conditions.Processes to significantly reduce pathogens (PSRP) —such as aerobic/anaerobic digestion, air drying,composting, lime stabilization or their equivalent —are most commonly used to meet Class Brequirements. Class B biosolids contain somepathogens, so certain site restrictions are required tominimize the potential for human and animal contactfollowing their application to land. All biosolids thatare land applied must, at a minimum, meet Class Bpathogen reduction standards. Site restrictions forClass B biosolids address public access to a landapplication site and crop harvest and grazing ofanimals at the site. Restrictions are summarized inTable 6.

Land use Period after biosolids application

Public access to the land:• High potential for public exposure (parks, playground, golf courses) Restricted for 1 year• Low potential for public exposure (farmlands, remote lands, securely Restricted for 30 days

fenced land)

Crops to be harvested or grazed:• Food crops, feed crops or fiber crops Can harvest after 30 days• Food crops with harvested parts that touch biosolids/soil mixture and Can harvest after 14 months

are totally above the ground surface (e.g., melon)• Food crops with harvested parts below the land surface, e.g., root crops

such as carrots– where biosolids remained on the land surface > 4 months prior to Can harvest after 20 months

soil incorporation– where biosolids remained on the land surface < 4 months prior to Can harvest after 38 months

soil incorporation

• Turf grown on land where biosolids are applied that will be placed on Can harvest after 1 yearland with high potential for public exposure or on a lawn

• Grazing land No grazing for 30 days

Table 6. Site restrictions associated with Class B biosolids application (adapted from USEPA, 1994a).

The goal of Class A biosolids requirements is toreduce the pathogens to below detectable levels.Processes to further reduce pathogens (PFRP) — suchas heat treatment, composting, heat drying, beta rayand gamma ray irradiation, pasteurization andthermophilic aerobic digestion — are most commonlyused to meet Class A requirements. Class A biosolidsare essentially pathogen-free with no restrictionsrelative to pathogens for land application and usuallyare sold or distributed in urban areas for gardening,landscaping or turf fertilization.

The goal of Class B biosolids is to ensure thatpathogens have been reduced to levels that do notpose a threat to public health and the environment

17


Vector attraction reductionThe attractiveness of biosolids to vectors is the thirdparameter of biosolids quality. Vectors are animalssuch as birds, rodents and insects that might beattracted to biosolids and therefore have the potentialto transmit pathogenic organisms (if present) tohumans. Ten options to meet vector attractionreduction requirements when land applying biosolidsare described in Part 503 and state Part 24 Rules.These options can be grouped into two generalapproaches:

• Preventing vectors from coming into contact withthe biosolids by use of physical techniques such asbiosolids incorporation and biosolids injectionbelow the soil surface within specified time periods.

• Reducing the attractiveness of the biosolids tovectors with specified organic matter stabilizationprocesses such as composting, digestion or addingalkaline/lime material.

Options to accomplish vector attraction reduction donot apply when bulk or non-bulk biosolids orbiosolids derivatives meet criteria for ExceptionalQuality (EQ).

Organic pollutantsOrganic pollutants in biosolids are not regulated inPart 503 because organic pollutants meet at least oneof the following criteria (USEPA, 1995b):

• The organic pollutants of potential concern havebeen banned or restricted for use in the UnitedStates and are no longer manufactured here.

• The pollutants are not present in biosolids atsignificant frequencies of detection (i.e., 5 percent)according to data gathered in the National SewageSludge Survey (NSSS).

• The limit for the pollutant identified in the biosolidsrisk assessment is not expected to be exceeded inbiosolids that are used or disposed, according todata from the NSSS.

NutrientsPart 503 requires that biosolids should be applied toagricultural land at the agronomic rate, the rate that isequal to or less than the amount of nitrogen (N)needed by the crops. The agronomic rate (calculatedon a dry-weight basis) is intended to:

• Provide the amount of plant-available N needed bythe crop or vegetation.

• Minimize the amount of N that passes below theroot zone to groundwater.

In addition, the Part 24 Rules include the followingcondition to the Part 503 definition of agronomic rate:

• Consider the amounts of phosphate (P2O5) andpotash (K2O) added by the biosolids as part of thetotal nutrient management plan for the crop to begrown.

Limiting the biosolids N loading to the fertilizer Nrecommendation should result in the impact ongroundwater being no greater than that of normalagricultural operations using fertilizer or manure.Though biosolids application rates that exceed theagronomic rate may increase the risk of nitrateleaching losses to groundwater, in some cases thismay be acceptable. For example, biosolids applicationto a reclamation site that exceeds the agronomic ratemay achieve a more stable and desirableenvironmental condition. Such cases may include butare not limited to reclamation sites where there is littleor no potential for nitrate to leach down togroundwater or where the groundwater cannot beused as a potable water supply. Typically, biosolidswill be applied at a high rate only once to improve the

18


soil physical properties and supply N and othernutrients for establishing a vegetative cover. Once avegetative cover has been established, future biosolidsapplications would be limited to the agronomic rateonly.

Wildlife and endangered speciesThe EPA also evaluates ecological risks — i.e.,potential adverse effect on plants and animals — forland application of biosolids. Of concern are wildlife,plants and endangered species that spend their entirelives on land receiving biosolids. Under Part 503,biosolids may not be applied to land if they are likelyto adversely affect a threatened or endangered speciesor its designated critical habitat. One recommendedstep for making the threatened and endangeredspecies determination is to contact the Fish andWildlife Service (FWS) Endangered Species ProtectionProgram in Washington, D.C., or one of the FWS fieldoffices.

Monitoring frequency and staterule prohibitionPart 24 Rules require the following, in addition to thefrequencies specified in Table 7:

• If the monitoring of biosolids or a biosolidsderivative indicates a pollutant concentration inexcess of its PCL, then the monitoring frequencyshall be increased to not less than twice that shownin Table 7.

• A person who applies biosolids shall perform a soilfertility test on soils sampled from each applicationsite before initial biosolids application. The personshall resample and test these soils on a regular basis,so that the last soil fertility test is not more than twoyears old at the time of the next biosolidsapplication.

• A person shall not knowingly apply biosolids frommore than one source or septage to the same landapplication site within the same crop year.

Amounts of biosolidsa Amount of biosolidsa Frequency(metric dry tons per (English dry tons per365-day period) 365-day period)

Greater than zero but less than 290 Greater than zero but less than 320 Once per year

Equal to or greater than 290 but less Equal to or greater than 320 but less Once per quarterthan 1,500 than 1,650 (4 times per year)

Equal to or greater than 1,500 but less Equal to or greater than 1,650 but less Once per 60 daysthan 15,000 than 16,500 (6 times per year)

Equal to or greater than 15,000 Equal to or greater than 16,500 Once per month(12 times per year)

Table 7. Frequency of monitoring for pollutants, pathogen densities and vector attraction reduction (adapted from MDEQ, 1999).

a Either the amount of bulk biosolids applied to the land or the amount of biosolids received by a person who prepares biosolidsfor sale or give-away in a bag or other container for application to the land (dry-weight basis).

Isolation from existing: Distance (feet)

Injection or surface application Surface applicationwith incorporationa without incorporation

Municipal wellb 2,000 2,000

Non-community public water supply 800 800

Domestic well 100 150

Homes 100 150

Commercial buildings 100 150

Surface watersc 50 150

19


Additional regulatory restrictionsrequired by Part 24 RulesMichigan Part 24 Rules include additionalrequirements beyond those specified in the federalPart 503 Regulations. The additional requirementsdiscussed thus far include: an expansion of the Part503 definition of agronomic rate to include takingcredits for the amounts of P2O5 and K2O added bybiosolids toward the fertilizer recommendations;increased frequency of monitoring if any pollutantconcentration exceeds its PCL; sampling and fertilitytesting of soils where biosolids are to be applied atleast every two years; and a restriction against septageor biosolids from another TWTDS being applied to asite that previously received biosolids in the samecrop year.

Part 24 Rules also address phosphorus (P)management, in addition to N management, for soilsreceiving biosolids applications. Biosolids cannot be

applied to agricultural land if the Bray P1 soil testlevel exceeds 300 lb P/acre (150 ppm) or if theMehlich 3 soil test is greater than 340 lb P/acre (170ppm). For forestland and tree farms, biosolids cannotbe applied if the Bray P1 soil test level exceeds 200 lbP/acre (100 ppm) or the Mehlich 3 soil test levelexceeds 220 lb P/acre (110 ppm).

Part 503 includes a general restriction againstapplying bulk non-EQ biosolids any closer than 10meters (approximately 33 feet) from waters of theUnited States; Part 24 Rules specify isolation distancesfrom wells, surface waters, homes and commercialbuildings. These isolation distances for bulk biosolidsthat are applied to land are listed in Table 8. Finally,Part 24 Rules also specify that biosolids must beapplied in a manner that will maintain a minimum30-inch separation distance between the soil surfaceand groundwater at the time of a biosolidsapplication.

a Incorporation must be within 48 hours unless a shorter time period is specified in these rules.b The term includes water supplies for facilities such as schools, restaurants, industries, campgrounds, parks and hotels.c Surface waters do not include grassed drainage ways or drainage ways that are tilled or planted.

Table 8. Required isolation distances from wells, surface waters, residences and commercial buildings for land-applied bulk biosolids (MDEQ, 1999).

20

The factor of greatest concern in the past washigh concentrations of heavy metals inbiosolids and the potential for accumulation

of metals in agricultural soils and crops. Metalconcentrations, however, have been significantlyreduced by industrial pretreatment programsmandated for industries discharging into sewagecollection systems. To illustrate this decrease, Table 9shows the quality of biosolids produced in Michiganin 1980 and recent data on pollutant concentrationsin biosolids sampled nationally in 1988 and 1996.These data, which are also compared with the Part503 PCLs and CCLs, reflect the decline in pollutantconcentrations during the past 15 to 20 years.

This improved quality is also shown graphically forMichigan biosolids in Figure 3, where averagepollutant concentrations present in biosolids in 1980are charted against the average concentrations foundin biosolids in 1995 and 1997. Again, these pollutantconcentrations are compared with PCLs and CCLsand clearly show two conclusions. First, except forarsenic, all pollutant concentrations in Michiganbiosolids have decreased, and in most cases, by morethan half of the 1980 concentrations. Second, currentaverage pollutant concentrations in Michiganbiosolids are well below the Part 503 PCLs used as astandard for “exceptional quality” biosolids.

The USEPA classes biosolids into four categories onthe basis of pollutant concentrations, pathogen levelsand vector attraction reduction controls (see Table 10):

1) Exceptional Quality (EQ) biosolids — Biosolids thatcontain all pollutant concentrations at levels belowthe PCLs and meet Class A pathogen reductionlimits and a vector attraction reduction thatreduces the level of degradable compounds. To

accomplish the pathogen and vector requirements,these biosolids are typically treated by alkalinestabilization, composting or heat drying.Generally, EQ biosolids can be applied as freely asany other fertilizer or soil amendment to any typeof land, whether used in bulk or sold or givenaway in bags or other containers.

2) Pollutant Concentration (PC) biosolids — Biosolidsthat meet the same PCLs as EQ biosolids butusually meet only Class B rather than Class Apathogen reduction requirements. Though someClass B biosolids meet the 38 percent volatilesolids reduction for vector attraction reduction,site management practices used for pathogencontrol will also accomplish vector attractionreduction. Class B biosolids that are PC must beapplied using injection or incorporation to preventexposure of biosolids pathogens to humans andanimals. Biosolids that meet PC criteria can beapplied to many types of land but not to lawns,home gardens and other lands with a highpotential for public exposure unless they are ClassA. Unlike EQ biosolids, PC biosolids may beapplied only in bulk and are subject to generalrequirements and management practices.

3) Cumulative Pollutant Loading Rate (CPLR) biosolids— CPLR biosolids typically exceed at least one ofthe PCLs but have no pollutants that exceed theCCLs. Such biosolids must be applied to land inbulk form. The cumulative levels of biosolidspollutants applied to each site must be trackedand cannot exceed any CPLR. Biosolids can beeither Class B (most typical) or Class A, and vectorattraction reduction must be implemented.

Biosolids Quality

Trace Michigan NSSS AMSAelement medianb meanb medianb PCLb CCLb

(pollutant) (1980) (1988) (1996)

Arsenic 8 6 5.4 41 75Cadmium 11 7 4.4 39 85Chromium 130 40 62.0 — —Copper 580 460 416 1,500 4,300Lead 270 110 75.7 300 840Mercury 2 4 1.8 17 57Molybdenum 32 11 12.0 — 75Nickel 49 29 35.0 420 420Selenium 32 5 4.1 100 100Zinc 1,200 720 744 2,800 7,500

21

B i o s o l i d s Q u a l i t y

4) Annual Pollutant Loading Rate (APLR) biosolids —These biosolids are Class A biosolids sold or givenaway in a bag or other container for application tothe land and have pollutant concentrations thatexceed one or more of the PCLs but do not exceed

any of the CCLs. These biosolids must be used atrates that do not exceed APLR requirements andmust be accompanied by information on a label orinformation sheet that includes instructions ontheir proper use.

Table 9. Biosolids trace element concentrations from the NSSS (USEPA, 1990), AMSA (Pietz et al., 1998) andMichigan biosolids (Jacobs et al., 1981) compared with Part 503 concentration limits of pollutants (USEPA, 1994b)a.

a Michigan biosolids sampled from > 200 TWTDS in 1980; NSSS = National Sewage Sludge Survey samples taken in 1988; AMSA = Association of Metropolitan Sewerage Agencies samples taken in 1996.

b Concentrations in mg/kg (dry-weight basis).

22


Type of Meets all Meets all Vector Site General Trackbiosolids and CCL PCL attraction restrictions requirements addedclass of pathogens reduction and management pollutant

practices

EQ Class Yes Yes Treatment No No Nobag or A optionsbulk

PC Class Yes Yes Any No Yes Nobulk Aa optiononly

Class Yes Yes Any Yes Yes NoB option

CPLR Class Yes No Any No Yes Yesbulk A optiononly

Class Yes No Any Yes Yes YesB option

APLR Class Yes No Treatment No Yesb Yesc

bag A optionsonly

Table 10. Summary of regulatory requirements for the four categories of biosolids (USEPA, 1994b and 1995a).

a If biosolids meeting Class A pathogen reduction requirement follow options 9 or 10 (incorporation or injection) for vectorattraction reduction, the biosolids must also meet Part 503 general requirements and management practices and would not beconsidered EQ biosolids.

b The only general and management practice requirement that must be met is a labeling requirement.c The amount of biosolids that can be applied to a site during the year must be consistent with the annual whole sludge application

rate that does not cause any of the APLRs to be exceeded.

120

100

80

60

40

20

0

75

41

11 11 8

Arsenic Cadmium

85

39

30

5 4

Mercury SeleniumMolybdenum

57

17

4 2 2

60

2113

75

85

41

100 100Currently there is no PCL

for molybdenum

Arsenic, cadmium, mercury, molybdenum and selenium concentrations compared with CCL and PCL.

8000

7000

6000

5000

4000

3000

2000

1000

0Copper Zinc

4300

1500760

508 459

7500

2800

1800

919 831

900

800

700

600

500

400

300

200

100

0

840

300 320

7661

420 420

13059 46

Nickel

Copper and zinc concentrationscompared with CCL and PCL.

Lead and nickel concentrationscompared with CCL and PCL.

CCL PCL 1980 MSU Study 1995 1997

Lead

23


Figure. 3 Average pollutant concentrations in Michigan biosolids in 1980 vs. 1995 and 1997 compared with the CCLs and PCLs (recent biosolids concentrations by personal communication with MDEQ).

24

Nutrient Value of Biosolids

Plant nutrient Range Mean Median

%

Total N 0.03 – 29.0 4.38 4.09NH4-N <0.01 – 12.0 1.42 1.10Total P <0.01 – 22.3 3.22 3.05Total K <0.01 – 13.0 0.43 0.24

Table 11. Nutrient content of Michigan biosolids produced by 157 TWTDS in 2000 (personal communication with MDEQ).

Research and experience have shown thatbiosolids can be beneficial both as a soilconditioner and as a source of nutrients.

Biosolids contain appreciable amounts of essentialnutrients for plant growth, especially N and P. Allbiosolids are typically low in potassium (K) becausemost of the K remains with the treated TWTDSeffluent that is discharged. Biosolids also containother essential plant nutrients — calcium,magnesium, sulfur, boron, copper, iron, manganese,molybdenum and zinc. When biosolids are stabilizedby high lime treatment, they can also have some valueas a liming material for acid soils and can substitutefor agricultural lime.

For agricultural soils, biosolids are generally appliedto meet the N needs of a crop. The exact ratio of thesenutrients will not be that of a well balancedformulated fertilizer, but nutrients in biosolids can becombined with nutrients from commercial fertilizersto provide the proper amounts of nutrients needed forcrop production.

Variations in the wastewater treatment processes usedby TWTDS throughout Michigan generate biosolidsthat vary in chemical, biological and physicalproperties. Data in Table 11 illustrate the typicalmacronutrient content of biosolids produced by 157Michigan TWTDS in 2000. If one uses the medianvalues for N-P-K, on average biosolids in Michigancould be expected to contain about 34 pounds ofplant-available N (PAN), 140 pounds P2O5 and 6pounds K2O per dry ton.

Nitrogen in biosolids Nitrogen may be present in biosolids and soils in twobasic forms: inorganic nitrogen (ammonium N andnitrate N) and organic nitrogen — i.e., carbon-basedcompounds such as proteins and amino acids. Themajority of the N in most biosolids is present asorganic forms with smaller amounts present asammonium N (NH4-N) and only trace amountspresent as nitrate N (NO3-N). The proportion ofNH4-N and organic N in biosolids will vary with the

25

Nu t r i e n t Va lue o f B i o so l i d s

treatment or stabilization process(es) used at theTWTDS (see Table 1 for treatment processes).Anaerobically digested biosolids can contain moreNH4-N than organic N, while lime-stabilized biosolidswill contain mostly organic N (because of NH4-Nbeing volatilized by high pH conditions). Also, freshlydigested biosolids usually contain more mineralizableN than do biosolids produced with more intensivestabilization processes such as composting.

The form in which N is present in biosolids is a keyfactor in determining how much PAN is available tofertilize the plant. Inorganic N (NH4-N and NO3-N) isavailable immediately after application. In contrast,organic N compounds are slowly converted viamicrobial activity (called “mineralization”) toinorganic or plant-available forms, so only a part ofthe organic N will be available for plant use. Theamount of organic N is typically estimated bysubtracting the concentrations of NH4-N and NO3-Nfrom the total N [i.e., total N – (NH4-N + NO3-N) =organic N].

When biosolids are applied on the surface rather thaninjected into the soil, NH4-N can be lost as ammoniagas (NH3) into the atmosphere. Estimates of NH4-Nloss by volatilization after surface application range

from 30 to nearly 100 percent of the NH4-N applied,depending on weather conditions (i.e., temperature,wind, etc.) and the length of time biosolids are left onthe soil surface. Table 12 lists values used in Michiganfor NH3 volatilization losses from soils after manureapplication, and these values should be applicable forbiosolids as well. Therefore, the amount of PANprovided by a biosolids application will depend onthe retention of NH4-N and the extent of organic Nmineralization.

Phosphorus, potassium andother plant nutrients in biosolids Biosolids contain varying concentrations of macro-and micronutrients required for plant growth. Like N,P in biosolids is present in both organic and inorganicforms, but the majority (70 to 90 percent) of this P isinorganic (Wolf and Baker, 1985). This inorganic P ispresent as aluminum (Al), calcium (Ca) and iron (Fe)phosphates and adsorbed to Al, Fe and manganese(Mn) hydrous oxides; also, some organic P isconverted to inorganic P by mineralization. Unlike N,P is not mobile and leaching of P to groundwater isinsignificant. Repeated applications of biosolids at N-based rates, however, can cause P to accumulate in

Days to incorporation NH4-N retained NH4-N lost

Injection 100% 0%

0 – 1 day 70% 30%2 – 3 days 40% 60%4 – 7 days 20% 80%> 7 days 10% 90%

Table 12. Estimated losses of NH4-N by volatilization of ammonia gas when manure is surface applied and thenincorporated (Jacobs, 1995).

26

Nu t r i e n t Va lue o f B i o so l i d s

surface soils over time and increase the risk of non-point source pollution losses to surface waters.Therefore, biosolids application strategies will need toconsider P loadings for sustainable land applicationprograms. As discussed earlier, Part 24 Rules restrictbiosolids application when the Bray P1 soil fertilitytest level for cropland exceeds 300 lb P/acre or forforestland exceeds 200 lb P/acre.

As shown in Table 11, the concentration of the othermajor plant nutrient, K, in biosolids is typically low.Because of the water solubility of K, most of the K inthe sewage received by the TWTDS remains in thewater and is discharged with the treated effluent.Therefore, biosolids are a poor source of K for plant

growth, but the amount of K2O added by a biosolidsapplication should still be credited toward the K2Ofertilizer recommendation.

Because biosolids are produced by treatment ofhuman sewage (see Figure 2), one can expect to findbackground concentrations of all the other essentialplant and animal nutrients in biosolids, in addition toN, P and K. These essential nutrients include most ofthe Part 503 pollutants listed in Table 5 except Cd, Pband Hg. Therefore, returning biosolids to croplandprovides the opportunity to recycle these nutrientsback to soils so they can be reused to grow moreplants and produce more animal products.

Establishing and ManagingSuccessful Biosolids Land

Application Programs

Many aspects of developing successfulprograms for applying biosolids toagricultural land have been addressed by

the federal Part 503 Regulations. Some additionalrequirements for biosolids application programs arespecified in the state Part 24 Rules, intended tofurther ensure that these programs would protecthuman welfare and the environment while providingbenefits to users of biosolids and the society thatproduces these residuals.

Many technical aspects for successful programs havealready been discussed, but some others will bediscussed in this section and recommended, even

though they are not required by Part 503 Regulationsor Part 24 Rules. Though paying close attention tothese technical issues is extremely critical to have asuccessful program, it is just as critically importantnot to forget about the non-technical aspects ofimplementing and maintaining successful landapplication programs.

Chief among the non-technical aspects is acceptabilityof this practice by the local community, farmers andrural residents near fields where biosolids are applied.Management and oversight of a land applicationprogram must be done well to earn the public’sconfidence and trust in the TWTDS and accomplish asuccessful program. Issues of importance in public

27

Es t ab l i sh ing and Manag ing Suc c e s s f u l B i o so l i d s L and App l i c a t i on P rog r ams

acceptability include public health, food safety,neighborhood nuisances, community land values,marketability of crops, sustainability of farmland andthe reliability of safe farming practices (NationalResearch Council, 1996).

Despite the existence of extensive regulations, publicperceptions of significant risks associated withbeneficial reuse land application programs still persistin some areas. Extensive evidence has shown theimportance of public education and the public’s earlyinvolvement in helping decide whether a biosolidsland application program is the right option for theircommunity. Sectors of society that are hesitant or maybecome hesitant to endorse the concept of beneficialreuse of biosolids will need to have evidence thatadequate surveillance and enforcement of federal andstate regulations will be accomplished (NationalResearch Council, 1996).

Site selection and landavailabilitySite selection procedures can begin once thesuitability of the biosolids for application toagricultural soil has been established, the public hasdecided to try land application for managing theirbiosolids, and a rough estimate is made to ascertainthat sufficient land area is available for a landapplication program. A number of factors such as thenature of the soil and its trafficability, natural andartificial drainage, permeability and water-holdingcapacity should be considered in determining sitesuitability. These factors will influence whenapplication equipment can enter fields withoutdamaging soil structure and the times of the yearwhen soil conditions may be too wet for makingbiosolids applications. Also, land slope, as well aspotential for erosion to a wetland or surface waters,may also affect site suitability. Part 24 Rules prohibit

surface application of biosolids to land having a slopeof more than 6 percent or subsurface injection ofbiosolids to land with more than a 12 percent slope.Climate — as it relates to the length of the growingseason, the type of cropping pattern and accessibilityto the site — is an important consideration in systemdesign. For instance, there will be some times of theyear when soils are too wet or frozen for biosolidsapplications.

Another consideration is that biosolids arecontinuously produced but farmers have landavailable only during certain times of the year. Someflexibility is possible, depending on the crops to begrown. For example, row crops (soybeans, corn, etc.)are planted in the spring and harvested in fall, so landis available before planting and after harvesting.Cereal crops such as wheat, oats and barley areharvested in July, opening land for biosolidsapplication in late summer and early fall. Corn cut forsilage will make land available about a month earlierin the fall than corn grown for grain. Hay ground isalso available after each cutting is harvested andremoved from the field.

Liquid biosolids can be applied to grass or forage crops withminimal soil disturbance using special sod injectors, such asthis injection unit in use at Port Huron, Mich.

28


Determining agronomic rates for biosolids applications The quantity of biosolids applied to farmland is basedon the agronomic rate, which is determined primarilyby the N and P concentrations in biosolids and thefertilizer recommendations for the crop to be grown.Designing the agronomic rate for individual fieldsrequires knowledge of expected yield of the crop to begrown, soil fertility test data and fertilizer recommendat-ions for N-P-K, and the nutrient content of biosolids,especially the amount and forms of N (organic N, NH4-N and NO3-N), so the PAN can be determined. Theexpected yield level of the crop will influence theamount of nutrient uptake and removal and is used todetermine the N-P-K fertilizer recommendations for thecrop to be grown. Information about biosolidsapplications in previous years will also be needed tocorrect the fertilizer N recommendation for carryover ofmineralized N (residual N) added by these previousbiosolids additions.

Soil fertility testing before application of biosolids isrequired by Part 24 to determine the soil fertilityconditions, fertilizer recommendations and the

suitability of soil pH for crop production. Maintainingappropriate soil pH for good field crop production isimportant to ensure that essential plant nutrients willbe available for optimum plant growth. Maintaining apH level at 6.0 to 7.0 is not required by Part 503 orthe Part 24 Rules, but maintaining the soil pH near aneutral reaction (pH 6.5 to 7.0) is a recommendedmanagement practice for optimum and maximumfield crop production. Unless biosolids are limestabilized, biosolids application will have little effecton soil pH. However, repeated applications of lime-stabilized biosolids may cause the soil pH to exceed7.0 and could result in plant growth problems.Therefore, monitoring and maintaining proper soil pHis critical for good crop production.

Basing the application rates of biosolids on crop Nneeds will maximize rates per acre and reduce thetotal number of acres needed each year. Because theamount of N required by crops is usually greater thanthe amounts of other plant nutrients, the croprequirements for most other nutrients except K willtypically be met when the agronomic N rate isapplied. However, biosolids application rates basedon N fertilizer recommendations will usually addmore P than the crop needs and/or more than theP2O5 fertilizer recommendations suggest. The reasonis that biosolids supply about the same amounts of Nand P2O5 to the soil, but most crops require only one-fifth to one-half as much P as N.

Soils have a great capacity to retain P, so some excessP2O5 can be applied to help build up P fertility levelsin a soil, but continued use of annual biosolidsapplications based on crop N requirements will likelycause the soil P level to become too high over time. Asexcess P accumulates in the soil, high soil P test levelsmay increase the risk of losing P in runoff and erosioninto surface waters. To avoid this, Part 24 Rulesrequire that biosolids applications be discontinued ifthe Bray P1 soil test reaches 300 lb P/acre (150 ppm)

Soil sampling and soil fertility testing are practices required byState Part 24 biosolids rules to ensure that biosolids nutrientsare properly managed.

29


or higher until nutrient harvest by crops reduces Ptest levels below 300 lb/acre. Periodic soil fertilitytesting can be used to monitor how fast the soil P testlevel is increasing so that biosolids applications can beproperly managed to avoid reaching this high Bray P1test level. Applying biosolids at rates based onexpected crop removal of P and suspending biosolidsapplications on certain fields for one or two years arealso management strategies that can help.

Once the agronomic rate or a lower rate of biosolidshas been decided on, the crop producer will need tocomplement (or supplement) the nutrients suppliedby the biosolids to provide the balance of nutrientscalled for by the fertilizer recommendations. As wasnoted earlier, biosolids are a poor source of K, soadditional K2O will need to be applied. Whenbiosolids are not applied at an N-based rate, then Nwill also need to be supplemented with commercialfertilizer. Finally, as with any crop productionprogram, good crop and soil management practices,including pest control, will be needed to ensuresuccessful agricultural production.

Biosolids applicationThe timing of biosolids application must be scheduledaround tillage, planting and harvesting operations.Timing will also depend on the crops to be grown, theclimate and weather, and soil physical properties.Application should not be made on wet soil during orimmediately after heavy rainfalls because traffic onwet soils may cause soil compaction, leave ruts in thesoil and reduce crop yields. In addition, muddy soilsalso make vehicle operation difficult and invite publicobjection by tracking mud out of the field ontoroadways.

Biosolids can be applied to the land using surfaceapplication (sprayed or spread on the soil surface andleft), incorporation (mixing surface-applied biosolids

into the soil) and injection (direct placement ofbiosolids below the land surface). Both liquid anddewatered biosolids may be applied with or withoutsubsequent soil incorporation. To be left on the soilsurface, biosolids would have to be EQ or Class Abiosolids with appropriate vector attraction reduction.Surface application with incorporation is limited tosoil with a slope no greater than 6 percent (Part 24Rules). Unless a minimum-tillage or no-till croppingsystem is being used, surface-applied biosolids mustbe incorporated by plowing or disking afterapplication. The sooner that biosolids are mixed intothe soil, the lower the ammonia volatilization and lossof N for crop growth (see Table 12).

Subsurface injection is the method of applicationmost commonly used in Michigan because mostbiosolids in Michigan are applied as Class B liquidslurries. Subsurface injection minimizes runoff fromall soils, can be used on slopes up to 12 percent, andwill minimize potential for odor problems andunpleasing aesthetics. Injection on sloping landshould be done perpendicular to the slopes to avoidhaving liquid biosolids flow downhill along theinjection slits and pond at the bottom of the slopes.

Liquid biosolids are transported to agricultural fields by largetankers and then transferred to applicators for injection intothe soil (Benton Harbor–St. Joseph land application program).

Good management is the key to a successfulland application program for biosolids.Following the federal Part 503 and the state

Part 24 Rules will help maximize potential benefitsand minimize potential hazards. The use of highquality biosolids, coupled with proper management,should safeguard the consumer from contaminatedcrops and minimize any potential adverse effect onthe environment. At the same time, good managementis critically important in achieving social acceptanceand earning the public trust by not creating anuisance when conducting a land applicationprogram. With both management objectives in mind,many communities will find that the application ofmunicipal biosolids to agricultural land is a goodchoice.

30


Monitoring programA final factor to consider is regular monitoring of thebiosolids application program. Periodic biosolidsanalyses are required to determine nutrient andpollutant concentrations so agronomic rates that willprovide crop nutrient needs can be calculated.Biannual (every two years) soil fertility testing,including soil pH, will help determine N-P-K fertilizerrecommendations and indicate whether any limemust be added to maintain soil pH at 6.0 to 7.0. Thistype of monitoring is required by Part 503 and/or Part24. Where high rates of biosolids are used (i.e., a non-agronomic or reclamation rate), additional monitoringof surface and tile drainage waters, groundwater, planttissue, soil, etc., may be needed and required by theMDEQ. However, more intensive monitoring will notbe necessary where high quality biosolids are appliedat agronomic rates to provide plant nutrients.

Injectors like these place liquid biosolids several inches belowthe soil surface to prevent odor nuisance problems, providesubsoil tillage, and accomplish an aesthetically-pleasingapplication.

Conclusion

31

References

Brown, S., and R.L. Chaney. 2000. Combining by-products toachieve specific soil amendment objectives. p. 343-360. In J.F.Power and W.A. Dick (eds.) Land Application of AgriculturalIndustrial, and Municipal By-Products. Soil Science Society ofAmerica, Inc., Madison, WI.

Chaney, R.L., S.L. Brown, J.A. Ryan, J.G. Hallfrisch, Q. Xue, T.I.Stuczynski, and H. Compton. 2001. Using biosolids, composts,and tailor-made biosolids mixtures in remediating urban andbrownfield sites and other metal-contaminated soils. 28 p. InProc. Innovative Uses of Biosolids – A Symposium, Sept. 17-19,2000, Chicago, IL. CD-ROM, Water Environmental Federation,Alexandria, VA.

Chaney, R.L., and J.A. Ryan. 1993. Heavy metals and toxic organicpollutants in MSW-composts: Research results onphytoavailability, bioavailability, fate, etc. p. 451-506. In H.A.J.Hoitink and H.M. Keener (eds.), Science and engineering ofcomposting: Design, environmental, microbiological andutilization aspects. Renaissance Publications, Worthington, OH.

Jacobs, L.W. 1995. Utilization of animal manure for crop production.Part II. Manure application to cropland. Bull. MM-2, MSUExtension, East Lansing, MI.

Jacobs, L.W., M.J. Zabik, and J.H. Phillips. 1981. Toxic organicchemicals and elements in Michigan sewage sludges –significance for application to crop land. p. 478-486. In Proc.Fourth Annual Conference of Applied Research and Practice onMunicipal and Industrial Waste, Sept. 28-30, University ofWisconsin—Extension, Madison, WI.

MDEQ. 1999. Administrative Rules, Part 24. Land application ofbiosolids (Promulgated pursuant to Part 31 of the NaturalResources and Environmental Protection Act, 1994 PA 451, asamended). Surface Water Quality Division, Michigan Departmentof Environmental Quality. 34 p.

National Research Council. 1996. Use of reclaimed water and sludgein food crop production. National Academy Press. Washington,DC. 177 p.

Pietz, R.I., R. Johnson, R. Sustich, T.C. Granato, P. Tata, and C. Lue-Hing. 1998. A 1996 sewage sludge survey of the Association ofMetropolitan Sewerage Agencies members. Report 98-4,Metropolitan Water Reclamation District of Greater Chicago,Chicago, IL. 49 p. plus 6 Appendices.

Rubin, A.B. 1997. USA: General. In P. Matthews (ed.) A global atlasof wastewater sludge and biosolids use and disposal. Scientificand Technical Report No. 4, International Association on WaterQuality, London, England. 197 p.

USEPA. 1990. National Sewage Sludge Survey; Availability ofinformation and data, and anticipated impacts on proposedregulations; Proposed rule. November 9, 1990, Federal Register55:47210-47293.

USEPA. 1992a. Sewage sludge use and disposal rule (40 CFR Part503) – Fact Sheet. EPA-882-F-92-002. Office of Water, Fact SheetWH-556. U.S. Environmental Protection Agency, Washington,DC.

USEPA. 1992b. Technical support document for reduction ofpathogens and vector attraction in sewage sludge. EPA R-93-004.U.S. Environmental Protection Agency, Washington, DC.

USEPA. 1994a. Land application of sewage sludge. A guide for landappliers on the requirements of the federal standards for the useor disposal of sewage sludge, 40 CFR Part 503. EPA/831-B-93-002b. Office of Enforcement and Compliance Assurance, U.S.Environmental Protection Agency, Washington, DC. 62 p.

USEPA. 1994b. A plain English guide to the EPA Part 503 biosolidsrule. EPA/832/R-93/003. Office of Research and Development,U.S. Environmental Protection Agency, Washington, DC. 176 p.

USEPA. 1994c. Biosolids recycling: Beneficial technology for a betterenvironment. EPA 832-R-94-009. Office of Water, U.S.Environmental Protection Agency, Washington, DC. 32 p.

USEPA. 1995a. Process design manual. Land application of sewagesludge and domestic septage. EPA/625/R-95/001. Office ofResearch and Development, U.S. Environmental ProtectionAgency, Washington, DC. 290 p.

USEPA. 1995b. A guide to the biosolids risk assessments for the EPAPart 503 Rule. EPA832-B-93-005. Office of WastewaterManagement, U.S. Environmental Protection Agency,Washington, DC. 144 p.

USEPA. 1999a. Environmental regulation and technology. Control ofpathogens and vector attraction in sewage sludge. EPA/652/R-92/013, Revised 1999. Office of Research and Development, U.S.Environmental Protection Agency, Washington, DC. 177 p.

USEPA. 1999b. Biosolids generation, use, and disposal in the UnitedStates. EPA 530-R-99-009. Solid Waste and Emergency Response,U.S. Environmental Protection Agency, Washington, DC. 74 p.

WEF-USEPA. 1997. Biosolids radionuclide information sheet.Biosolids Fact Sheet Project, Water Environment Federation,Alexandria, VA. 7 p.

Wolf, A.M., and D.E. Baker. 1985. Criteria for land spreading ofsludges in the Northeast: Phosphorus. p. 39-41. In D.E. Baker,D.R. Bouldin, H.A. Elliott, and J.R. Miller (eds) Criteria andrecommendations for land application of sludges in theNortheast. Penn. Agric. Exp. Stn. Res. Bull. No. 851, ThePennsylvania State University, University Park, PA.

MSU is an affirmative-action, equal-opportunity institution. Michigan State University Extension programs and

materials are open to all without regard to race, color, national origin, gender, religion, age, disability, political beliefs,

sexual orientation, marital status, or family status. • Issued in furtherance of Extension work in agriculture and home

economics, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Margaret A.

Bethel, Extension director, Michigan State University, E. Lansing, MI 48824. • This information is for educational

purposes only. References to commercial products or trade names do not imply endorsement by MSU Extension or

bias against those not mentioned. This bulletin becomes public property upon publication and may be printed

verbatim with credit to MSU. Reprinting cannot be used to endorse or advertise a commercial product or company.

New 12:01 - 1M - KMF/KP - Price $.50, single copy free fto Michigan residents

MICHIGAN STATEU N I V E R S I T Y

EXTENSION

utilizing biosolids on agricultural land - michigan …warncke/e2781 utilizing biosolids on...u.s....

Documents