treatment and disposal of potato wastesinfohouse.p2ric.org/ref/15/14204.pdf · treatment and...

'Aedia and Reagent for Micro- "CO Laboratories, Inc., Detroit. and OSBORNE, M. F. 1950.

ON, W. O., and HENDEL, C. S. Pat. 2,705,679. WRRI, "puffs" potatoes. Food

, R. M. 1951. Quick cooking

t3-1836.

.E, C. W. 1955. Maintenance isms. Appl. Microbial. 3, 361-

new snack item-French fried

the technology, production and ypt. Agr. Misc. Publ. 695. WILLIAMS, J. H. 1945. U. S.

'ON, W. 0. 1955. Process of 'Pat. 2,707,684. ato snack item. Bakers Weekly

3., and HEISLER, E. G. Potato 18-73-15. ilip confections. Can. Food Inds.

The chemicals we get from po-

I, C. F., HEISLER, E. G., and uation of potato chip bars. Food

p ~ . 190-194.

Treatment and Disposal of Potato Wastes

R . E . Pailthorp J. W. Filbert G . A. Richter

20 P 05765

Pollution control is a pressing problem for existing processing plants and is a major consideration when comparing locations for new processing plants. Reduction of processing losses must be considered during the manufacture of the product to obtain the greatest economic returns and to ensure the lowest amount of polluting emuents. Pro- cessing plants with low product losses will have a low amount of waste.

There is a demand for more and better finished products and also a demand for maintaining and improving the quality of U. S. public waters. The demand for increased water quality has been instrumen- tal in the formation of a U. S. national policy that demands substantial treatment of processing wastes before they can be discharged to U. S. public waters. The potato-processing industry has developed methods for providing effective removal of settleable and dissolved solids from potato-processing wastes.

The types, sizes, layouts, and details of treatment systems must be carefully considered and planned to obtain maximum benefits from the investment. In some cases this portion of a processing plant will be as important as the proper selection of the product process line. Reduc- tion of the total quantity of waste through selection and operation of efficient peeling systems and processing lines and reduction of water flow through conservation and water reuse systems should be the first step in a pollution control program.

747

748 R. E. Pailthorp, J. W. Filbert, and G. A. Richter

POLLUTION

Treatment of industrial wastes is necessary if effluent is discharged to public waters in the United States. Treatment may also be required prior to irrigation or other forms of land disposal. Pollution can be defined very broadly as anything that causes nuisance conditions in or adjacent to a receiving stream or anything that interferes with another beneficial use of a stream or groundwater. Pollution is not a quantitative term. However, many laymen consider a stream polluted only when apparent nuisance conditions exist.

The following are some things that can cause pollution: (1) organic wastes (domestic sewage, food-processing wastes, cattle feed-lot drainage, etc.); (2) bacteria; (3) toxic compounds (chlorine, lead, hex- avalent chrome, mercury, etc.); (4) nutrients (phosphates, nitrates); (5) floating material: (grease, oils, foam, etc.); (6) settleable materials: (ashes, soil, organic materials); (7) cloudiness (turbidity); (8) soluble ions in high concentrations (sodium, chloride, sulfate, nitrate); (9) acids and alkaline wastes; (10) heat; and (11) color.

The most common pollution problem is associated with organic wastes, which undergo decomposition in water. The decomposition occurs when bacterial and other biological forms use the compounds as a food source. Oxygen is required for biological decomposition to take place without causing nuisance conditions in a stream. The oxygen for this process is taken from the stream. Only 9-10 mg/liter of oxygen will dissolve in water. Many forms of aquatic life require 4-5 mg/liter of oxygen to survive.

When all of the oxygen is used from a stream it becomes unattrac- tive; fish die, odorous gasses evolve, and decomposing solids float on the surface. As a consequence of this type of pollution, recreation is destroyed, and many other beneficial uses are impaired or destroyed.

Treatment of industrial effluents to remove organic materials often alters many other objectionable waste characteristics.

Terminology The pollution control and effluent treatment field has its own termi-

nology. Some of the most common terms must be learned to under- stand literature on pollution control and to evaluate statements made by representatives of control agencies and other people in the field of pollution control. The following is a glossary of the most common terms. Many of these will be used in this chapter.

20. Treatment and Disposal of Potato Wastes 749

Domestic Sewage. Wastewater from residential dwellings, apart- ment houses, and other living accommodations.

Commercial Sewage. Wastewater from commercial establishments containing domestic sewage, along with possible other wastewaters such as those originating from laundries, bottling plants, ice plants, and restaurants.

Industrial Wastes. Wastewater from industries using large volumes of water for processing industrial products, such as food-processing plants, paper mill refineries, and textile mills.

BOD.-Biochemical oxygen demand is a measure of the oxygen necessary to satisfy the requirements for the aerobic decomposition of the waste. This provides an accurate measure or indication of the organic content or pollution strength of the waste.

BOD,.-Measurement of oxygen required in a 5-day laboratory test. BOD &.-Measure of ultimate BOD; usually measured using a 20-

day test. COD.-Chemical oxygen demand is a measure of the amount of

oxygen that will react chemically with a waste. This value varies with the type of oxidant used, with the testing method used, and with the type of waste. The result is not a direct measure of BOD, but can usually be correlated with BOD by a series of parallel tests.

Suspended Solids.-Solids which can be mechanically filtered from the wastewater.

Settleable Solids.-Suspended solids that will settle in sedimentation tanks in normal detention periods.

Total Sol ids.-Both suspended and dissolved solids. Parts Per Million.-The pounds of material in one million pounds of

Milligrams Per Liter.-The milligrams of material in one liter of

Primary Treatment.-The removal of suspended and settleable sol-

Secondary Treatment.-The removal of organic matter by biological

Advanced Waste Treatment.-Treatment beyond secondary treat-

Aerobic Treatment.-Biological activity in the presence of dissolved

Anaerobic Treatment.-Biological activity in the absence of dis-

Toxicity.-Usually measured by placing fish or other aquatic life

\

flow (abbreviated as ppm).

flow (abbreviated as mglliter).

ids by screening, flotation, or sedimentation.

decomposition (usually preceded by primary treatment).

ment.

oxygen (normally does not cause odors).

solved oxygen (normally does cause odors).

750 R. E. Pailthorp, J. W. Filbert, and C. A. Richter

C

SUSPENDED DISSOLVED SOLIDS SOLIDS

SUSPENDED DISSOLVED VOLAT I L E VOLATILE

I 1


forms in the waste or diluted waste for several hours and noting fatalities.

Testing The waste characteristics must be known to properly size effluent

treatment units and to evaluate the effectiveness of treatment units after they are installed. In some cases, these characteristics may be estimated from production records and losses, but sampling and testing of the effluent discharged from the plant is usually necessary. The most common measurements are those of various types of solids and of chemical or biological oxygen demand. The test procedures for solids determinations and for BOD can be found in “Standard Methods for the Examination of Water and Wastewater” (Amer. Public Health Assoc. 1985).

Figure 20.1 represents the relationship of the various classifications of solids in liquid waste. The settleable solids portion represents the amount of waste that can be removed by sedimentation.

The COD test is easier and quicker to run than the BOD test. A BOD test requires 5 days before the results are known; a COD test can be done in a few hours.

1 I TOTAL SOLIDS I

I / N0N.S E T T L E A B L E

/ SUSPENDED FIXED I

SETTLEABLE DISSOLVED FIXED

Fig. 20.1. Classification of solids in wastewater

Regulations Regulations contralling surface waters and groundwater pollution

are established by county, state, and federal agencies. The regulations usually establieh an upper limit on several pollutants in the final

effluent. In some cases receiving water standards have been established when discharge limits are not appropriate to protect the environmen t .

Common law rulings are another facet of pollution that should al- ways be considered by an industry that discharges wastes. Even though a discharge meets the requirements set forth by a regulatory agency, a judgment can be obtained by court action against the dis- charger. Many industrial plants conduct extensive stream surveys above and below their discharge points in an effort to protect against common law actions.

History The history of waste treatment for the potato-processingindustry

parallels that of many other industries. In the United States, there are three geographical areas of major potato-processing activity: (1) Idaho, eastern Oregon, and eastern Washington; (2) North Dakota and Min- nesota; and (3) Maine. Most plants are located in sparsely populated areas where the waste load from the plants is extremely large compared to the domestic sewage load. Because of this, the waste was traditionally disposed of in streams.

Potato chip and prepeeled potato plants in contrast, while expanding in number and size, are largely located near metropolitan areas, where the waste effluent is more easily handled by municipal facilities. In general, these plants are much smaller than French fry or dehydrated potato plants, and the processes do not contribute as great a unit waste load as the other types.

A typical example of the recognition of a problem and the approach to solution was found in Idaho along the Snake River. During the 1950s, the potato-processing industry in this area experienced great growth and the stream was subjected to increased demands for irrigation and recreation. Fish kills and other nuisance conditions resulted. Therefore, in early 1961, the State Department of Health required the potato processors to provide for removal of all settleable solids and up to 90% reduction of BOD in the future.

The processors of the region formed a joint committee (Potato Pro- cessors of Idaho) and undertook pilot-plant studies to determine the best way to provide the required treatment. By the processing season of 1964, most of the plants had installed primary treatment for removal of settleable solids. Stream conditions were materially improved by the primary treatment systems. This same committee fi-


nanced a pilot-plant study in 1964 and 19 to evaluate secondary treatment methods to meet the requirements for 90% BOD reduction. The results of the study were used to design a full-scale aerobic secondary treatment facility at the R. T. French Company in Shelley, Idaho, as a federal demonstration project.

Since the installation of primary treatment, the Potato Processors of Idaho have sponsored many research projects to explore various types of aerobic and anaerobic treatment, waste biological solids treatment, conditioning, disposal, and spray irrigation.

By the beginning of the 1971-1972 processing season, most Idaho potato-processing plants had initiated either secondary treatment or spray irrigation systems.

Most of the information on potato-processing waste treatment has been published since 1950. There were very few treatment systems for potato wastes in the United States until after 1960.

CHARACTERISTICS OF PROCESSING PLANT EFFLUENTS

Components of Potato-Processing Waste The composition of a waste stream from a potato-processing plant is

largely determined by the processes used. Most potato processing can be separated into the following general steps: washing the raw potatoes; peeling, which includes washing to remove softened tissue; trimming to remove defective portions; shaping, washing, and separation; heat treatment (optional); final processing or preservation; and packaging.

The analysis of waste stream from potato-processing operations re- lates closely to the composition of the potato. Components foreign to the potato that also may be present include dirt, caustic, fat, cleaning and preserving chemicals, and other food ingredients in small quantities. A typical proximate analysis of potato waste solids from a plant employing steam or abrasive peeling is shown in Table 20.1. Normally, most waste streams in the plant are combined before discharge from the plant.

Dirt. Dirt or silt adhering to the surface of the potato is removed either in an initial washing step or in the normal peeling waste stream. It contributes to the suspended, fixed solids and normally is treated separately from the other process water. For example, this water can be


Table 20.1. Percentage Composition of Potato Waste Solids

Component Amount (%)

Total organic nitrogen as N 1.002 Carbon a s C 42.200 Total phosphorus as P Total sulfur as S Volatile Solids

0.083 0.082

95.2

settled in a shallow pond or clarifier. The water from these systems contains soluble and suspended solids and must be treated for discharge.

In-plant treatment and recycle of wash water has been'practiced. Treatment units available include screens, clarifiers and high-pressure liquid cyclone units. Some wash water is usually bled from these recycle systems and must be treated prior to discharge.

Raw Pieces. Raw pieces that are not suitable for processing range in size from whole potatoes to small fragments. Since these materials are normally firm, they present little problem in removal by screening or settling. These are commonly used for cattle feed.

Raw Pulp. Raw potato that has been finely subdivided is usually designated as raw pulp. Sources of this include abrasion peeler discharge, cutting waste, and pulp from starch separation. Equipment handling raw potatoes will contribute finely divided raw potato solids when the equipment is cleaned. Because of the large amount of water normally in contact with the pulp, much of the soluble solids are leached out. The raw pulp may be removed from the waste stream by fine screening or settling. Raw starch settles from such streams so rapidly that it sometimes causes plugging of lines and cleaning problems. Pulp is commonly used for cattle feed.

Cooked Pulp. The softening action of heat during peeling or processing steps weakens the intercellular bonds of the potato tuber and results in separation of large quantities of potato cells and agglomerates of cells during washing and handling steps. These rapidly dis- perse in the wastewater. Many such agglomerates are removed in screening, but the greatest portion passes through the normal 20-mesh screen opening. These solids settle rapidly in a properly designed clarifier and represent a major portion of the settleable solids removed in


primary treatment of potato-processing waste streams. Separated solids are used for cattle feed.

Dissolved Solids. Constituents of the potato that are readily water ? soluble appear as dissolved solids in the final waste stream. These include solubilized starch, proteins, amino acids, and sugars. This organic portion of the waste stream can be removed only by secondary treatment, namely some form of biological oxidation or land disposal. Starch plant waste characteristics are given in Table 20.2.

Effect of Process Variations in process methods make it virtually impossible to make

generalizations concerning the quantities of waste produced by specif- ic operations. Many references can be found for studies made in the major types of processing plants. These studies show wide variations in water usage, peeling losses, and methods of reporting the waste flow.

In many cases, the data do not define whether the waste was screened before analysis. Several studies on the composition of wastes resulting from various types of potato processes are summarized in Table 20.6.

Processes involving several heat treatment steps, such as blanching, cooking, caustic and steam peeling, will obviously produce an effluent containing gelatinized starch and coagulated proteins. In contrast, starch processing and potato chip processing produce emuents in which the components have not been heated. The disposal of starch protein water has been the subject of much research.

Design of Effluent Treatment Facilities For an existing plant, it is necessary to measure the flow of all waste

streams and determine the quantity and character of the solids found in these flows. Procedures for accomplishing this are well known. Of major importance is the reduction of waste discharge into the final plant emuent and the reduction of water flow throughout the plant.

For a proposed new plant for which the waste facilities must be designed, informption may possibly be found in the literature for a similar installation. In most cases, however, a reasonable estimate of the waste flow may be determined from the estimated capacity of the plant, the recovery of product expected, and the type of screening and clarification equipment to be installed. Accurate estimates of water

u? OOONO omu3wcn NN4 4

I I I I I

I I I I I

I I I I I

I I I I I

T??ZZ -+"mm

I I I I I

I I I I I

a - 2

OOONO u? O"CD2 "4

I I I I I

I I I I I

I I I I I

I I I I I

-'u??u?cq O N A W Q , l- lnlnroln

I I I I I

I I I I I

756 R. E. Pailthorp, J. W. Filbert, and G . A. Richter

msmrvatlon L rwao of ..tar

Procam. r*wlalonn

Procam control

MW product8

usage and methods of re-use to be employed are, of course, necessary. For preliminary estimates, it can be assumed that 1 lb of dry potato solids exerts a BOD of 0.65 lb and a COD of 1.1 lb. %r..nlnp

WASTE TREATMENT PROCESSES

The conventional waste treatment process is usually considered to occur in three phases: primary treatment, secondary treatment, and advanced waste treatment (AWT). Primary treatment involves the removal of suspended and settleable solids by screening, flotation, and sedimentation. Secondary treatment involves the biological decomposition of the organic matter, largely dissolved, that remains in the flow stream after treatment by primary treatment processes. Biolog- ical treatment can be accomplished by mechanical processes or by land disposal. The primary treatment process is frequently sufficient to safeguard public health and to prevent development of nuisance conditions in instances where large volumes of dilution water are available in receiving streams. Where the flow in the receiving stream is low or where pollution loads are high, secondary treatment must generally be provided. In 1974, the Environmental Protection Agency proposed na- tionwide minimum discharge limits for the potato-processing industry, which resulted in land disposal or secondary treatment (EPA 1973).

Advanced waste treatment involves removal of pollutants that are not removed by conventional secondary treatment. Advanced treatment can include removal of nutrients, suspended solids, and organic and inorganic materials.

In mechanical secondary treatment processes, the organic material remaining in the effluent from primary treatment processes receives further treatment by passing the flow through units in which biological oxidation of this organic matter takes place. Biological oxidation is a result of biological organisms using the organic matter as a food source. The flow from the biological units is then passed through sedimentation units so that the biological solids formed in the oxidation unit may be removed prior to the final discharge of the treated effluent to a stream. When irrigation is used as the secondary treatment system, bacteria in the topsoil stabilize the organic compounds. In addition, the soil may accomplish removal of some ions by adsorp- tion or ion exchange. Ion exchange in some soils may cause system failure. In all cases, careful consideration must be given first to the steps that might be taken within the plant to reduce the waste load.

Treatment Category

U n i t Processes

U n i t Sequence


Primary Treatment Sadlnantbtlon

S r t t l l n p pond1

Secondary Treetment Tr lck l lnp

I l l t a r 8 & t I watmd

S t m b l l l i a t l o n ponds

Anmwoblc fILtmr8

An..I-ObtC contact

Anaerobic pond8

&?.rad pond.

ILUdpD

Advanced Treatment C h r l c a L t r s a W O t

Cnrbon t r n m w n t

F1Ltrat lon

Ion mchanpa

hr.,.. 0..0.l.

A l r i t r lpp lnp

I

I r r l p a t t o n

Fig. 20.2. Generalized unit process sequence for waste disposal.

%BOD Removal - 6 t o 10X 4 0 t o 60s 86 t o 8 5 1

I

I Stream

Treatment -4-1 L l q u l d - C o n o e n t r n t l o n

1 I C a t s l a F a a d

L n n d f l L L I n o l n a r . t l o n I S o l i d s C m t t l . C . t t l .

D isposa l I F m m d I F g * d I Fig. 20.3. Typical treatment sequence for potato-processing effluent.

758 R. E. Pailthorp, J. W. Filbert, and G. A. Richter 20. Treatment and Disposal of Potato Wastes 759

S I L t S e p n r a t f o n

S n t t l l n g P o n d S e c o n d a r y T r n n t m e n t r l t h P a e l l n g ond

C L o r l f f e r Procasslng W e s t e s W a t e r S t r e n m

I I -Yrf lor I S o l l d s

I L l q u l d I L V O C U U D F I L t e r

O r n v y T h t o k e n e r

S o L l d o D l o p o r n L

Fig. 20.4. Procedure for silt water treatment.

The sequence of steps involved in treating potato-processing emuent are outlined in Figs. 20.2-20.4 and described in detail in the following sections.

In-Plant Treatment Two main objectives are immediately evident in reducing waste dis-

posal problems within the plant. The first is to minimize the solids disposed of into the waste stream by improved control of the processing and handling equipment and methods. The second is the use of minimum quantities of water in processing. In many plants, the reduced losses, improved product recovery, and reduced water usage resulting from attention directed to these areas to reduce treatment costs has more than offset the cost of treatment facilities.

Steps that have been taken to reduce the loss of solids to plant waste streams include the following:

Improvements in peeling facilities to obtain a cleaner potato with less loss of solids. Reduction of floor spillage by redesign of equipment. Collection of floor waste in receptacles that can be dumped instead of washing waste into floor drains. Removal of potato solids from waste carriage water as soon as possible after their introduction to minimize solubilization of the solids. Replacing operational steps that create large losses where possible. Avoiding conveying.

The peeling process contributes by far the largest quantity of waste to the plant emuent. Therefore, improvements in peeling efficiency can have a major effect on the waste treatment cost. Examples of steps that can be taken include better control of caustic concentration in caustic peeling, use of higher-pressure water sprays in washing facilities, circulation of caustic through peeling equipment to obtain better heat transfer, use of preheat facilities to reduce losses in both steam and caustic peeling, and use of continuous abrasion peelers rather than batch units.

Reducing the water flow in the plant has two advantages. The size of treatment facilities is influenced by total water flow from the plant. Second, the efficiency of a primary settling system, or the quantity of waste that will be removed by a given piece of equipment, increases with the concentration of the waste.

Water usage within the plant can be significantly reduced by the reuse of process water containing only minimum quantities of dissolved or suspended solids where fresh water is not necessary. For example, overflow from water cooking, water blanching, water cooling, and surge tanks can be used to remove peel after lye or steam treatment of potatoes. To avoid plugging nozzles in the washer, the process water should be screened first. Water used in the exit end of peel-removal washers following lye or steam peeling can be screened and pumped into the spray system at the entrance end of the washer. Process water can be used to furnish flume water for conveying raw potatoes from storage areas into the plant. Water used to defrost refrigeration coils can be used to replace fresh water in the plant.

To reduce the possibility of bacterial contamination of the product, fresh chlorinated water should be used in the final steps of processing such as the final washing of blanched potatoes before dehydration. In- plant cleaning practices may require improvement to reduce bacterial buildup in lines carrying reclaimed process water. This water is frequently warmed, allowing bacterial growth to flourish if care is not taken. The advantages of reduced waste treatment and water usage will greatly outweigh the additional sanitation problems if they occur. Excessive foam production may be difficult to control in water reuse systems if sufficient fresh water is not introduced.

Other steps that have been used to reduce the volume of emuent to be treated include (1) use of some method other than water fluming for conveying potatoes, (2) use of improved cleaning facilities for equipment and floors, such as shut-off nozzles for hoses and high-pressure, low-volume spray units, and (3) collecting clean waste streams and discharging to natural drainage or storm water systems.


Screening (Pretreatment) Screening is the first step in most treatment systems and is the most

economical method of removing large solids. Screening protects other treatment units from plugging or damage and reduces the size of other solids-handling units. The solids removed are relatively dry and can be disposed of with comparative ease. Screening is often used to remove larger pieces so that the water can be reused within the processing plant.

Three types of screens are commonly used: vibratory screens, rotary screens, and stationary gravity screens. Many screening devices have been custom-built for individual plants, but in most cases, standard manufactured units are more satisfactory. These units are similar to

Fig. 20.5. DSM screen for dewatering plant effluent-45 unit. (Courtesy Door- Oliver, Inc.)

I

r

!

I i

I j I

I j , !

i

i

! I I

i I I

i I

, I

I


Fig. 20.6. Rotary screen used in primary treatment. (Courtesy CH2M Hill.)

screens used in dewatering products during processing. Mesh size normally is 20 to 40 per inch (Figs. 20.5 and 20.6).

The question of the elevation and location of the waste screen is of considerable importance. In one design, plant wastewaters are collected in a sump pit below the floor level of the plant, from which they are pumped to the screen. The screen is elevated so that the solid wastes may fall by gravity into a suitable hopper. From here, the water flows by gravity into the primary treatment equipment or to the sewer.

Another method is to locate the screens below the level of the plant drains if the elevations permit. After screening, the solid waste can be conveyed up to the waste hopper and the water pumped into the clarifier, or other disposal system.

Primary Treatment In the past, the removal of floatable and settleable solids from food-

processing wastes was frequently done in a batch process. Two tanks


would be provided which could be operated on a fill and draw schedule. Modern treatment systems, however, use continuous flow-through tanks, called clarifiers, of either rectangular or circular construction (Fig. 20.7). The required geometry, inlet conditions, and outlet conditions for successful operation of such units are known. Clarifiers are fitted with mechanical scraper mechanisms, which collect the solids that settle to the bottom or float to the top so that they can be removed from the tank easily and continuously for further processing. Figure 20.8 shows a cross section of a typical circular clarifier. Construction materials and methods will vary because of local conditions, prefer- ences, and costs.

In the primary treatment of potato wastes, the clarifier typically is designed for an overflow rate of 800-1000 gal/ft2/day and a depth of 10-12 ft. Most of the settleable solids are removed from the emuent in the clarifier. Generally, this primary treatment results in a decrease of 40-70% of the COD.

To reduce the volume of the settled plant waste, which normally contains about 6% solids, some form of concentration is employed.

P L A N T EFFLUENT

-*

/ S C R E E N S PER S Q U A R E - F n n l

\ PER D A Y

.a\ F L O W M E A S U R M E N T

TREATED F L O W TO S T R E A M OR S E C O N D A R Y T R E A T M E N T \

C L A R I F I E R 800 G A L L O N S , . --.

C E N T R A T E OR

V A C U U M FILTER OR C E N T R I F U G E

S O L I D S 1.5 TO 20%

J

Fig. 20.7. Primary treatment schematic diagram.


WEIR

_. WCRAPERS MOVE SOLIDS SOLIDS WITHDRAWAL TO HOPPER HOPPER

Fig. 20.8. Primary clarifier.

Belt-type vacuum filters are used for this purpose. Additional dewatering of the underflow by pressing has not been successful.

The withdrawal of the underflow from the bottom of the clarifier is accomplished by pumping. The solids that result from caustic peeling will, of course, have a high pH. The optimum pH level for best vacuum filtration of solids has been found to vary considerably from plant to plant. However, when the underflow withdrawal is adjusted to hold the solids in the clarifier for several hours, biological decomposition will start and the pH of the solids will be lowered substantially. At a pH of between 5 and 7, these solids will dewater on a vacuum filter without the addition of coagulating chemicals. It was originally thought that both lime and a ferric salt would be necessary to condition the solids from caustic peel plants before they could be dewatered successfully on vacuum filters, but they did not prove necessary.

The solids produced as a result of steam or abrasive peeling operations also undergo biological degradation in a few hours. If this decomposition proceeds too far, the solids will be difficult to dewater. A very low pH in the clarifier as a result of biological activity will cause damage to the structures and equipment. Agitation and internal mixing within the clarifier caused by excess fermentation and accompany- ing gas evolution greatly decrease the efficiency of separation. Control of the treatment process, especially the sludge withdrawal rate, must be maintained to prevent these problems.

Flotation is another method of solids removal. This process uses fine


gas bubbles, which are caused to form and attach to suspended solids. The gas bubbles float the solids to the surface of the tank where they are skimmed off by mechanical collectors. Several commercial units of this type are available.

Secondary Treatment Several biological systems are used to provide secondgry treatment

(Fig. 20.9). In all cases, the secondary treatment units must provide an environment suitable for the growth of biological organisms, which do the actual work of waste treatment. Some of these treatment units depend on a sufficient supply of oxygen to support aerobic decomposition of the organic matter. Aerobic biological decomposition is prac- tically odorless and is capable of very high removal of the organic matter contained in wastes. In some cases, anaerobic systems may be used for secondary treatment.

Fig. 20.9. Secondary waste treatment facility. (Courtesy R.T. French Co.)


Most of the full-scale potato waste secondary treatment systems have been constructed since 1968 although considerable research of a pilot-plant scale had been conducted prior to that time. The R. T. French Company took one of the first steps with a full-scale federally supported project to demonstrate activated sludge treatment of their potato division waste in Shelley, Idaho. Since the R. T. French project, many other potato processors have installed biological treatment systems or land disposal irrigation systems.

The unit processes described in the following sections differ in the method of providing the environment necessary for the biological action that occurs during secondary treatment. These various processes are the principal means of achieving secondary treatment. Data on a number of pilot-scale and full-scale secondary treatment designs are presented in Tables 20.3 and 20.4.

Activated Sludge Process. Waste is discharged into large aeration basins into which atmospheric oxygen is diffused by releasing com- pressed air into the waste or by mechanical surface aerators (Fig. 20.10). The environment thus created is favorable to the growth of a heavy concentration of bacteria because of the presence of abundant organic food supply and oxygen. The organic content of the waste is removed by the life processes of the bacteria and stored within the bacterial mass as protoplasm. The bacterial mass, termed uctiuuted sludge, is then removed in sedimentation basins, thus providing highly treated eflluent. A diagram of an activated sludge system is shown in Fig. 20.11.

There are many variations of activated sludge processes; however, all operate in basically the same way. The variations are the result of unit arrangement and methods of introducing air and waste into the aeration basin.

Biological Filters. Waste is distributed over filter beds constructed of rocks 3-4 in. in size, plastic media, and wood media. Atmospheric oxygen moves naturally through the void spaces in the filter material. In the environment thus created, biological slimes, consisting mainly of bacteria, flourish and colonize on the rock surfaces. As the waste trickles over the surface of the biological slime growths, removal of organic matter is accomplished. As the slime growths become more and more concentrated, their attachment to the media surface is weak- ened and the biological growth is washed from the filter. The pro-

Table 20.3. Characteristics of Various Pilot-Scale Secondary Treatment Designs

Hydraulic Organic Treatment process and Type of process Daily organic loading removal

process modification water loading (detention time) (8) Remarks Reference Complete mixing acti-

vated sludge 4 days

2-4 days

- 50-60 COD

49-82 COD

No nutrient added

pH adjustment and nutrients added

No nutrients added

Anderson (1961)

95+ BOD

98 BOD

-

80 COD

95 BOD

90+ BOD

94 BOD

-

20 COD

Complete mixing activated sludge


Complete mixing activated slud e

Contact stabhzation activated sludge

Oxidation ditch activated sludge

Hi h rate trickling i G r s

Super-rate biofilter

Lagoons-treatment

Anaerobic lagoons with domestic sewage

Potato starch Less than 80 lb/ 1000 Ib

15 h r

6 hr min

8 hr min

Buzzell et al. (1964) ~ . . . .-

MLSSH/hro 191-358 lb BOD/ Lye peel

Lye peel

Lye peel

No nutrients added; no pH adjustment -

pH adjustment

Atkins and Sproul

Sproul (1966A)

Atkins and Sproul

Pasveer (1966)

Sproul (1966A) Buzzell et al. (1964) Hatfield et al. (1956)

Porges (1963)

Anderson (1961)

(1964)

(1964)

1000 ft3

1000 ft3 200-400 lb BOD/

1-1.5 hr con- - tact and 6-8 h r reaeration

- 3 days

70 lb BODllOOO ft3 158 gal/ft*/day

-

Potato starch

Corn process

Potato

Potato

water

NO nutrients added; filter clog ed

Nutrients acfded

Odor problems

Odor problems

159 ib BODllOOO

72-123 lb - 25 lb COD/1000 ft3 -

Recycle 5:l and ft3 1O:lc

BOD/acre

dcIntosh and McGeorge

lay and Furgason

:H2M Hill(1966)

:H2M Hill (1966)

2H2M Hill (1969)

(1964)

(1965)

Nitrogen added; pH adjusted

pH adjusted

n I

40 Ib BODllOOO ft3 - - 1 day

Less than 400 lb - 140 lb BOD/1000 20 hr

5 days 15 days

BOD/1000 ft3

ft3

ft3 112 lb BOD/1000 -

65+ in Anaerobic lagoons

Anaerobic lagoons heated to 50°C and completely mixed

Biological filter


Anaerobic contact

Corn process

Simulated sec-

Lye peel ,

Lye peel

Lye peel

water

ondary potato process water

winter . . - -. . -. 50 COD 70 COD 85-90 COD

Nutrients added

Nutrients added

Problems maintaining solids in system

Not fully acclimated

Avg. liquid depth = 5 f t

Steam peel oper.; little odor; liquid depth = 3 ft

Steam peel oper.; offensive odors; liquid depth = 3 ft

-

75 BOD

91 BOD

60 COD

2H2M (1970) 2H2M Hill (1970)

Porges (1963)

3lson et al. (1964)

70 BOD >40 COD Lye peel

Lye peel

Potato waste

Potato process + domestic waste

Potato process + domestic waste

58 lb BODllOOO ft3 - 29 Ib BODllOOO ft3 - Anaerobic filter

Anaerobic pond 111 BOD5 105 days

140 BOD5b - B1-level & anerobic

B1-level pond with

B1-level pond

pond

aerator Olson et al. (1964) 300 BOD5b - I

Source: Prepared by CHZM Hill, Corvallis, Oregon. a MLSS = mixed liquor suspended solids in aeration basis. b Lb/acre/day c Filter recirculation ration = number of times flow passed through filter.

Table 20.4. Characteristics of Various Full-Scale Secondary Treatment Designs

Treatment process and roCess Type of process Daily organic Hydraulic loading Organic modiication water loading (detention time) removal (%) Remarks Reference

2 days 73 BOD During sludge bulking ~~

Dry caustic peel 32-39 IbllOOO ft3 Complete mixing

Complete mixing

Complete mixing

Multiple aera te f

activated sludge

activated sludge

activated slud e

lagoons

Anaerobic pond and lye peel activated sludge

Trickling filters (2 stages)

Activated sludge and lye peel aerated lagoons

Lye peel 28-84 lb/1000 R3

Lye peel 60-180 IbllOOO ft3

Lye peel 3-6 lbl1000 ft3 in aerated lagoons

25-80 IbllOOO R3 to activated sludge

60 lb/1000 ft3

in aeration basin 55 lblac in aerated

8.&%?2 in aerobic

Dry caustic peel First stage-20-

60-150 IbllOOO ft3

lagoon

1-2 days

14 h r

16-20 days in aerated lagoons

105 days in aerobic lagoons

1 day

14 h r in aerated

52 days in aerated

60 days in aerobic

basin

lagoons

lagoon

70-90 BOD Removal varies with sludge bulking

Slud e bulking will refuce removal

Algal blooms will re-

87 BOD

98 BOD duce removal

95 BOD

85 BOD Cold temperature will

99 BOD

Slud e bulking will r e h c e removal

(both stages) reduce removal Slud e bulking and al- rf blooms will re-

uce removal

EPA (1973)

EPA (1973)

EPA (1973)

Landine and

EPA (1973) Dean (1973)

3 2 a %I 0

a c

0 CJ

L

z W

-I

U U W

a

4 c j a E 0

5 tz 4

I4 d

L-

a 0 c

:\ c

U P 0

a It! U

U P) c.

.- 2 2 c

z

I- < W < .

0 a


Fig. 20.13. Spray irrigation of potato waste. (Courtesy Rogers Bros.)

Anaerobic Systems. This grouping of systems includes all that em- ploy biological secondary treatment processes in the absence of oxygen. Anaerobic bacteria, those that live and consume organic matter in the absence of oxygen, make these systems possible. Organic pollutants are converted to bacterial protoplasm, carbon dioxide, water, and methane by anaerobic bacteria. Many of the bacteria required to make these systems function are, however, extremely sensitive to environmental conditions and changes in these conditions. Anaerobic systems are upset by changes in pH away from near neutral, oxygen, and temperature change, by introduction of heavy metals, etc. Several months are generally required to develop the necessary anaerobic bacteria in a system. Upset conditions can destroy process performance for long periods of time.

Advantages of anaerobic systems include (1) low capital costs of designs, (2) low operations costs, (3) production of a fuel by-product (methane), and (4) low waste sludge quantities. Disadvantages include (1) susceptibility to process failure, (2) odor problems, and (3) slowness in reaching peak eficiency.

Anaerobic systems include the following:


GAS METER

TOTAL VOL 1590 GAL POROSITY a A3 6 %

PmosITY 1OTAL VOL 1180 1s o x G A L ~3 2-5'0.vw18'OF MEDIA PRIMARY

CLARIFIER OVERFLOW

EOUALIZATION 1 1 1 TANK

PUMP

Fig. 20.14. Anaerobic filter flow diagram.

Anaerobic ponds. By-level ponds (anaerobic bottom layer and aerobic upper layer). Anaerobic filters (covered submerged biological filters employing rock or artificial media). The wastewater enters the filter from below and exits from the top. The anaerobic bacteria grow on and between the media (Fig. 20.14). Anaerobic contact systems (anaerobic activated sludge systems). A covered and mixed reactor is used in place of an aeration basin.

Solids Disposal Solids are one of the end products of nearly all waste treatment

processes. The effective disposal of the separated solids is necessary for the treatment process to be successful. The method of solids disposal may provide an economic return or add another cost to the treatment process.

Potato solids collected from primary treatment processes are dilute, only 4-7% and are difficult and bulky to handle. These solids can be concentrated to 15-18% solids by the use of belt-type vacuum filters or centrifuges. Both methods have been used successfully, but vacuum filtration is usually preferred.

Most concentrated potato solids recovered from processing plants

.


can be fed successfully to livestock. Concentrated solids recovered from primary treatment of waste from processing plants using either caustic or steam peeling make satisfactory feed. Discussions of the use of by-products of potato starch and potato processing for animal feed- ing were presented by Dickey et al. (1966) and Grames and Kueneman (1 969).

Waste biological solids (bacteria) grown as part of the secondary treatment process also have the potential to be satisfactory for cattle food. Such salids are typically about 35% protein. One current draw- back, however, is to find an economical method of concentrating the waste solids, which are 0.5-0.75% solids, as removed from the treatment process. While this problem is not peculiar to potato waste, biological solids from secondary potato wastewater treatment must rank among the most dificult to concentrate and dewater. This is primarily because of the presence of filamentous bacteria, which seem to thrive on the high-carbohydrate waste.

Advanced Wastewater Treatment Advanced wastewater treatment (AWT) encompasses a large num-

ber of individual treatment processes that can be employed to remove remaining organic and inorganic pollutants from secondary treated wastewater. The unit processes catagorized as AWT are principally physical and chemical in nature. Figure 20.15 is an example flow diagram using the AWT processes of coagulation and sedimentation, granular filtration, and chlorination. Additional data on AWT unit processes are given in Table 20.5.

LIME OR ALUM AN0 COAGULANT

-. FROM SECONDARY TREATMENT TO STREAM

MIXED MEDIA CHLORINE COAGULATION SEOIMENTAJION FILTER CONTACT

SYSTEM 15 MlNUTES lOD0 GALlFT /DAY 5 GAL/FTzNIN 1 HR. DETENTION

----%-----*

FILTRATION

FILTRATION

Fig. 20.15. Typical example of advanced waste treatment system flow diagram.

c3

m

n

4

776 R. E. Pailthorp, J. W. Filbert, and G. A. Richter 20. Treatment and Disposal of Potato Wastes 777

Filtration. Granular filtration, employing mixed media or moving bed filters, hold much promise for meeting anticipated future limitations on discharge of BOD and suspended solids from potato-processing operations. Following good activated sludge secondary treatment, most BOD within the secondary emuent is contained in bacterial solids. Removal of the suspended solids will greatly improve the effluent quality. Granular filtration is preferred to microstraining because of greater operational problems and lower solids removal efficiencies associated with microstraining. Secondary effluent should contain less than 250 mg/liter suspended solids to make filtration practical. In the event that higher concentrations of suspended solids are anticipated, the secondary emuent should be first passed through polishing ponds or subjected to chemical coagulation and sedimentation.

Chemical Coagulation and Sedimentation. In the event that removal of phosphorus is required from the wastewater, chemical coagulation with alum, iron salts, or lime is necessary. Lime should be considered for this purpose if ammonia removal is also required. Re- gardless of the primary coagulant employed, a large quantity of sludge is produced. Sludge lagooning is one of the few economical solutions to the sludge disposal, and this practice requires considerable land.

Other AWT Processes. Additional AWT processes now under development, which show promise of producing extremely high-quality effluent, include reverse osmosis and ultrafiltration. Advancement of the necessary membrane technology is required before these processes merit much consideration in selection of waste treatment unit processes. Reverse osmosis and ultrafiltration will probably find their first extensive application within inplant treatment and recycling systems.

Most of the AWT processes listed in Table 20.5, other than those discussed above, are expected to find little or no application in potato waste treatment during the foreseeable future. Associated costs are high when compared to benefits.

Other Treatment Methods Other treatment methods used for various industrial wastes are

anaerobic digestion, chemical precipitation, deep well injection, and foam separation. Some of these methods have been tried on a laboratory scale and others have known limitations.

APPLICATION IN POTATO-PROCESSING. INDUSTRY

The most commonly used methods of waste treatment in the United States have been screening, primary treatment and settling of silt water in earthern ponds before discharging to city sewers or separate secondary treatment systems. Figures 20.16-20.18 are photographs of equipment in primary treatment plants in operation at Idaho potato- processing plants. These primary treatment plants remove 40-70% of the BOD from screened plant wastes. A 20-mesh screen removes 15- 25% of the BOD of a combined waste discharged from a processing plant.

The quality of potato-processing effluents naturally improves as the degree of treatment increases. Table 20.6 shows the estimated effluent characteristics before screening, after screening, and after primary treatment for various types of potato wastes. Data on organic removal in various secondary treatment processes are presented in Tables 20.3 and 20.5.

Activated sludge treatment of potato waste has been accompanied

Fig. 20.16. Rotary screens.

--I-- .


Fig. 20.17. Belt-type vacuum filter.

Fig. 20.18. Potato plant clarifier.

C h i p C h i p C h i p Total p lan t s b m

peel, flake Total plant: u u s t i c

peel. flake Total plant: caustic

peel. flake Total plant: flour Total plant: caustic

p e l , flake Total plant: item

peel, flake French fries

Spray washer Trimming Cuttine Inepection Blanch Plant mmpoaite

French fries and starch plant

Steam peel Caustic peel Caustic peel Wash water P a l w s t e

Table 20.6. Potato-Processlng Eft luent Characteristics Before Screening

Nitrogen Tots1 Suapended Settleable Total .ollds ~ l l d s BOD COD wll& phwphomru, Total Ammonia

Typs of w s t e lmg/liter) (mg/liter) Imgiliter) lmg/liter) pH Img/literl lmg/liter) (mglliter) (mg/literl

6.000 1.750 - 1,643 800-2000 700-1900

'Prim table Blanch waste Combined plant

Waste

- 3,645 - - - - - - -

14.900 270 880 260

2.283 8,100

7,794 - -

11.550 700

1o.OOo- 15,000 600

1.600 -

- - - - - - - - -

2,830 4.5

150 32

1.470 1.790

6.450 - - -

100-250 10,OOo- 12.000

150-200 600-700

-

5.3 7.2 - - - - - - -

11.5 6.9 7 2 6.9 4.7

11.1

10.7 - - - 7.0

- 6.2 5.1

- Water Suspendad

wlidn BOD COD C.PlcitY Rocesl step or product qtyle (galltan) ( I b h n ) (Ibltan) (Ib/ton) pH (ton/&yl

usage

- - - Washina 264 2.76 1.35 Peeling-

Dry cauatic Wet caustic Steam

Trimming Slicing ~

Dehydrated Frozen

Blanching Dehydrated Fmzen

Cooling Cooking Dewaterin Fryer scrufber Fryer belt spray Refrigeration T r a n s p r l water Cleanup French fries Granules French fries and hash browns French fries French fries French fries French fries flakes and granules French fries: flakes and granules French fries French fries French fries French French fries. fries hash browns and flakes

Flakes Flakes, granules. d i m Granules and slices Granules Dehydrated productn French fries French fries and dehydrated product. Dehydrated products French fries Granules C h i p

347 719 573 190

183 364

42 250 160 117 123 100 100 384

70 228 - - - - - - - -

- - - - 14.62 19.1

57.2 40.41 30.37 26.8

0.52 1.55

0.59 I 4 2.6 5 2 5

- - - - - - - - - - -

- - - 1.40

2.34 2.38 0.94

10.9

- - - 0.52 5 . u - - - - - - - -

Table 20.6. (Continued) Table 20.6. (Continued)

Allcr P n n u r y Treatment After Sueeninrr

Total Suspended Settleable Total Nitmgen-

soli& d i & BOD COD solid. phosphorous, Total Ammonia d w u t a (mg/l ibr) (mg/l ibr) (mg/liter) (mgllitar) -pH (mg/l ibr) (mg/liter) (mg/literl (mg/liter)

3.350 1.280 - 6.7

Nitrugen Total Suspended Settleable Total - Mlids solids BOD COD MII& phmphororu. Tou l Amm Type of wa8b (mglliter) (mgllibri ( m g h b r i (mglliteri pH (mglliteri lmglliteri Img/llteri (mg/l

C h i p C h i p C h i p Total plant: ibam

' Total plant: u u t i c

Total plank caustic

Total plant: flour Total plant: caustic

peel. flake

peel. flake

peel, flake

wel. flake

C h i p Chip. C h i p Total plank stsrm

p l . flake Total p l an t caustic

peel. flake Total plant: u u t i c

peel. flake Total plant: flour Total plant: c a d c

pwl. flake Total plant: s t u m

Peel. ma French frier

Cuttinn &?&=*-

- 225 300 -

701 2.142

1.774 3.548

3,855 1.140 3,314 8.314

1,266 -

- - 3,640 732

- - 1.623 3.408

Tdtal p l an t steam peel, flake

French fries Spray washer Trimming Culting Inspection Blanch Plant composite

French fries and starch plant

Steam Cauitic peel peel

caustic peel Wash water Peel waate Trim table Blanch waste Combined plant

W a s t e

70 1 -

InspeeGon Blanch F " t mrnpdb

h n c h Ma .od 3.966 1.120 1.020 118

1.770 2,630 538 905

940 1.313 - -

.turh PlMt stsun Peel C a u t i c peal c . d c pes1 wuh watar

Trim table Blanch w u t a

P-1 W M b

Combined fiMt W U t O

Water S!MOe"ded

Dry Dcaustic Wet caustic Steam

Trimming Slicing

Dehydrated Fmren

Blanching Dehydrated Fmzen

Cooling Cooking Dewaterin Fryer Fryer belt scrufber spray

Refrigeration Transpart water Cleanup French fries Granulea French fries and h u h brawn8 French fries French fries French fries French fries flakes and granules French fries: flakes and granules French fries French fries French fries French fnes h n c h fries. h u h brawn8 and flakes Flakes Flakes granules dices Granuies and a l i k Granules Dehydrated products French fries French friea and dehydrated products Dehydrated pmducta French fried Granuled C h i p

B h c h i n g Dehydrated Froxen

Cooling Cookina D e w s t a k

Fryer belt .pray Rdngeratron Transpart water Cleanup French fnea Granules French fnea and huh browns Frnnch fned French fned French fnea French hen. flaked and grnnuled French hen, tlaLer and granuled French fned Fmnch fned

Rysr urufber - - - - - - 2830 2060 3490 3000 2610 2500 3070 3720 2420 2480 3220 2700 3000 2100 1860 1680 1565 2830 980 1530 1790 2310 2.980

- - - - - - 13.1 23.5

17.8 44.2 55.6 22.4 91.0 25.2 68.6 47.7

-

- - -

24.3 19.6 - - 10.3 23.6 7.6 25.0 -

- - - - - -

50.8 27.8 73.9 30.2 58.6 71.6 27.9 63.9 50.9 64.5 41.6 33.8 24.6 17.2 20.8 21.5 30.4 18.9 8.9 27.5 15.5 22.0 30.4

- 400 475 350 500 375 600 1250 1600 600 700 1150 800 loo0 240 650 600 550 375 500 150 250 200 500

French fried French friea French fried, hrsh bmwna and f l h Flakea Flakes, granule.. diw , Granules and slices Granules Dehydratedpmduct. , French fried French fried and dehydrated p r o d u N Dehydrated producta French fried C r i n u l a

780


Table 20.6. (Continued) R ~ M step or

, T y p Of W M k Remarkr Referenw product *tyle Referena

Chip Chip Chip

North Dako(r 2 galllb potatnw

T0t.l plant: steam peel. flake North Dakota

flake Nonh Dakota

Total plant. uustic pl. flake North Dakota

Total plant: flour North Dakota Total plant uustic p l .

Total PlUlt: U U h C p l .

ILL-

c.&c peel

C a d c peel

W u h watsr

66% COD removal; aver-

A 5 n g e 7 days. (North age 7 day (Idaho1

Dakota1 Idaho 1.250-1.500 gal/ton

Peal wrsts Caustic or ateam

Trim table

Blanch W M b

1.200-1.300 ea/% Caustic or steam ped- 600-600 galltnn

Caustic or steam p&l- 700-800 g a l / h

Combined plant w u b Caustic M steam 3.6.50-4.200 ga:-

Potata chi lnst. Intern. (19601 Olson et of (19651 Ollon t f of. (18651

Ollon ef of. (19651

Olson et ol. (19651

Olson tt of. (19651 Olson ef 01. (1965)

- Olson et of. (19661 Spmul (196681

Pailthorp and Filbert (19661

Kuenemn (1965)

Kuenemn (19651

Kueneman (1965)

Kueneman (19651

Kueneman (19651

Kuenemn (1965)

Kuenemn (1965)

Washing Peeling Dry caustic Wet uustic Steam

Trimming Slicing

DehydrBted Fmren

Blanching Dehydrated Frozen I

Cooling Cooking Dewiterin Fryer scrubber Fryer bell spray Refrigeration Trampor( water Cleanup French fries Granules French fries and h u h

browns French fries French fries French fries. flakes and

granules French fries. flakes and

French fries French fries. hash

browno and flaken Flakes Flakes granules diced Granulea and slices Granules Dehydrated produ- French friea French fries and dehy-

drated products

Dehydrated produd French fries G r a 4 B Chi=

EPA (19731 i I EPA (19731

EPA (19731 I EPA (1973) ' EYA (1973) j EPA 119731 1 EPA (1973) 1

EPA (19731 EPA (19731 EPA (1973l EPA (1873) EPA (19731 ' EPA (19731 ' EPA (19731 EPA (19731 EPA (19731 I EPA (19731 , EPA (19731 EPA (1973) 1

EPA (19731 EPA (19731 EPA (19731 EPA (19731

EPA (1973)

EPA (19731 EPA (19731 EPA (19731

EPA (1973)

EPA (19731 EPA (19731 EPA (19731 EPA (1973) EPA (1973) EPA (19731

EPA (19731 EPA (19731

I

Kueneman (19651 EPA (1973) EPA (1973) EPA (1973)

with some operation problems, primarily connected to sludge settling in secondary clarifiers. High-carbohydrate waste has historically been subject to filamentous bacterial or fungal growths if the aeration basin environmental conditions are not maintained in the proper ranges. Some of the environmental conditions are interrelated and include pH, temperature, food-to-microorganism ratio, sludge age, hydraulic detention time, nutrient level, micronutrient level, and dissolved oxygen level.

When filamentous bacteria or fungi appear in the aeration basin in a predominant quantity, the activated sludge settleability is greatly reduced, frequently resulting in solids being lost in the effluent with subsequent low BOD removal (6040%). When solids are not lost in the secondary clarifier effluent, the activated sludge system has provided BOD removal of 95% and above. The state of the art is not 782

advanced to the point, however, where the filamentous growths can be readily removed once they occur, and there are instances when the growths have appeared during periods of apparent ideal environmental conditions for better settling bacteria to predominate.

Some potato processors, who are located where suitable land is available at a reasonable price, have chosen to construct land disposal systems (either flood or spray irrigation) because of possible operational problems with a higher rate treatment system and pending no discharge legislation. A few processors have chosen to construct large lagoon systems in lightly populated areas.

While regulatory agencies are presently favoring land disposal irrigation of potato waste, extreme caution should be used to design and operation of this type of treatment system to avoid potential problems because of the limited historical data available.

MUNICIPAL TREATMENT

Some processing plants, because of necessity or choice, discharge a portion of all of the process waste to municipal sewer systems. The methods used by municipalities for charging for sewer service are specified by the Environmental Protection Agency if a federal grant is used for funding a joint treatment system.

It is often more economical for an industry to have a municipality provide waste treatment if (1) the waste treatment service charge has been based on the actual cost to treat the waste; (2) there is no possibility for a by-product recovery; (3) the waste can be handled by conventional treatment methods; or (4) inclusion of the waste with domestic and commercial sewage does not complicate the treatment process.

Municipalities can often provide treatment of industrial waste more economically than an industry for the following reasons:

Federal and state loans are available for municipal treatment plants. Municipalities can borrow money at low interest rates. Municipal financing is for periods of 15-25 years. Industries usually pay property taxes on the treatment facilities which they own. Sewer service charges are an operating expense to an industry and therefore have a tax advantage over a capital expense. Combined waste of a community may provide for a leveling effect for the wastes and result in less investment and better operation.

784 R. E. Pailthorp, J . W. Filbert, and G. A. Richter ‘LO. Treatment and Disposal of Potato Wastes 785

A large municipal plant should result in a lower cost per unit of treatment capacity and a lower operating cost.

Most city ordinances control the type of waste that can be discharged to the sewer system. These ordinances, in general, are intended to protect the materials of the sewer system, to protect workers in the sewer system, to minimize maintenance problems, and to control the discharge of materials that would be toxic to treatment processes. In some cases, municipal ordinances control the concentration of BOD and suspended solids that can be discharged to a municipal sewer.

A realistic method for limiting the amount of BOD and suspended solids discharged to a sewer system is to base the sewer service charge on the pounds of BOD, pounds of suspended solids, and flow discharged to the sewer system. The sewer service charge should be based on the cost of providing the service. This method of computing sewer service charges is covered in detail by a booklet entitled “Fundamental Con- siderations in Rates and Rate Structures for Water and Sewage Works,” which was published in the Ohio State Law Journal, 1951. The Environmental Protection Agency has also published rate struc- ture guidelines which parallel this.

An equitable sewer service charge must be based on a thorough study of the waste to be treated and the cost to the municipality. Negotiations of a rate based on detailed considerations of the wastes may result in a financial saving to an industry.

BIBLIOGRAPHY

ADLER, G. 1966. The production, use and disposal of potatoes in West Germany. Proc. Intern. Symp. Util. and Disposal of Potato Wastes, New Brunswick (Canada) Res. and Productivity Council, 1965, pp. 50-70.

ALLEN, T. S. 1962. Waste Reuse in the Food Processing Industries. Amer. SOC. Mechanical Engr. Publ. 72, PID, 11.

AMBROSE, T. W., and REISER, C. 0. 1954. Wastes from potato starch plants. Ind. Eng. Chem. 46, 1331.

AMER. PUBLIC HEALTH ASSOC., AMER. WATER WORK ASSOC., and WATER POLLUTION CONTROL FED. 1985. Standard Methods for the Examination of Water and Wastewater. Amer. Public Health Assoc. Washington, DC.

1961. A tentative approach to the establishment of engineering guide lines in the design of treatment facilities for waste associated with the manufacture of food products from potatoes. Thesis for Professional Engr. degree, Univ. of Idaho.

Feasibility of biological treatment of potato processing wastes. Proc. 19th Ind. Waste Conf., Purdue Univ.

A review of primary treatment processes. Proc. Intern.

ANDERSON, V.

ATKINS, P. F., JR., and SPROUL, 0.

BALLANCE, R. C.

1964.

1966.

Symp. Util. and Disposal of Potato Wastes, New Brunswick (Canada) Res. and Productivity Council, 1965, pp. 200-211.

BLACKSTOCK, H., and SKIVER, B. Potatoes nourish the Simplot processing empire. Food Eng. 46( 11) 59-65.

BURROWS, C. E. A primary treatment plant for potato chip industry wastes. Proc. Prod. and Tech. Div. Meetings, Potato Chip Inst. Intern., pp. 19-20.

BUZZELL, J . C., JR., CARON, A. L. J., RYCKMAN, S. J . , and SPROUL, 0. J. Biological treatment of protein water from manufacture of potato starch-Parts I and 11. Water Sewage Works, 327-330 (July), 360-365 (August).

1967. Biological treatment of potato wastes. Proc. 13th Pacific Northwest Ind. Waste Conf., p. 79.

1970. Advanced treatment of potato wastewater. Paper presented to Potato Processors of Idaho Association, Sun Valley, Idaho.

Reports of the Potato Processors of Idaho Association on Association pilot plant studies.

1964. Characteristics and amounts of potato wastes from various process streams. Proc. 19th Ind. Waste Conf., Purdue Univ., pp. 379-390.

CULP, R. L., and CULP, G. L. 1971. Advanced Wastewater Treatment. Van Nostrand Reinhold Co., New York.

DAUGHERTY, M. H. 1964. Activated sludge treatment of citrus waste. Water Pollu- tion Control Fed. J. 36(1) 72-79.

DAY, R. O., and FURGASON, R. R. Anaerobic stabilization of secondary potato wastes. Res. Rept., Univ. Idaho.

DICKEY, H. C., BRUGMAN, H. H., HIGHLANDS, M. E., and PLUMMER, B. E. 1966. The use of by-products from potato starch and potato processing. Proc. Intern. Symp. Utiliz. and Disposal of Potato Wastes, New Brunswick (Canada) Res. and Productivity Council, 1965, pp. 106-121.

Production and use of potatoes and the waste disposal problem in the U.K. Proc. Intern. Symp. Util. and Disposal of Potato Wastes, New Brunswick (Canada) Res. and Productivity Council, 1965, pp. 71-85.

Treatment of emuents from potato processing. Proc. Intern. Symposium Util. and Disposal of Potato Wastes, New Brunswick (Canada) Res. and Productivity Council, 1965, pp. 246-257.

Secondary treatment of potato processing wastes-final re- port. FWPCA Rep. FR-7.

By-products and waste in potato processing. Proc. 15th Ind. Waste Conf. Purdue Univ., pp. 99-106.

The manufacture of potato starch. Proc. Intern. Symp. Util. and Disposal of Potato Wastes, New Brunswick (Canada) Res. and Productivity Council, 1965, pp. 122-134.

1966. Basic concepts of the biological oxidation of organic wastes. Proc. Intern. Symp. Util. and Disposal of Potato Wastes, New Brunswick (Canada) Res. and Productivity Council, 1965, pp.

EPA. 1973. Development Document for Proposed Emuent Limitation Guidelines and New Source Performance Standards for the Citrus, Apple and Potato Segment of the Canned and Preserved Fruits and Vegetables Processing Plant Source Cate- gory. Rept. 44011 -731027. Environmental Protection Agency.

1948. European methods of the utilization of potato starch factory wastes. Am. Potato J. 25, 409.

1974.

1961.

1964.

CARLSON, D. A.

CHAPMAN, R. L.

CH2M HILL.

COOLEY, A. M., WAHL, E. D., and FOSSUM, G. 0.

1966, 1969, 1970.

1965.

DICKINSON, D. 1966A.

DICKINSON, D. 1966B.

DOSTAL, K. A.

DOUGLASS, I. B.

DOUGLASS, I. B.

1969.

1960.

1966.

ECHENFELDER, w. W., JR., and MULLIGAN, T. J .

212-234.

ESKEW, R. K.

treatment and disposal of potato wastesinfohouse.p2ric.org/ref/15/14204.pdf · treatment and...

Documents