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A SURVEY OF WASTEWATER TREATMENT PRACTICES IN THE BROILER INDUSTRY

Brian Kiepper, The University of Georgia, Engineering Outreach Program,

Driftmier Engineering Center, Athens, Georgia 30602

Presented at the 2001 WEF Annual Conference, Atlanta, Georgia ABSTRACT Traditionally, poultry processing operations have been large users of potable water, and consequently, large generators of wastewater. A typical poultry slaughter facility will generate 5-10 gallons of wastewater per bird processed, containing on average, >2,000 mg/L of biochemical oxygen demand (BOD), >4,000 mg/L of total suspended solids (TSS), and >3,000 mg/L of fats, oil and grease (FOG). With many plants processing 150,000 to 200,000 birds per day, the generation of 1.0 to 2.0 million gallons per day of high strength wastewater is typical. Most of the soluble and particulate organic material in the wastewater must be removed prior to discharge from the plant in order to achieve compliance with established environmental regulations. Depending on the degree of treatment required poultry processors have the option of utilizing physical, chemical and/or biological treatment systems. Each system type possesses unique treatment advantages and operational difficulties. To assist the poultry processing industry in determining the future focus of scientific and engineering research related to the treatment of wastewater, the U.S. Poultry & Egg Association (USPOULTRY) sponsored an independent University of Georgia Engineering Outreach Program survey aimed at identifying the current practices and experiences of the industry in the area of wastewater treatment. The survey was distributed nationwide. The completed surveys were complied and results are summarized in this paper. The survey goals were to determine the extent to which wastewater treatment processes are used by the industry, the context in which they are used, problems commonly encountered in their operation, and solutions that have been attempted to control such problems. Twenty-three poultry processing facilities, located in 11 states, returned completed surveys. Surveys were received from slaughter, further processing and rendering plants. Details on plant processing types, production levels, potable water use, wastewater generation and laboratory analytical testing are provided. Thirteen (57%) of the facilities reported wastewater treatment system operational problems. Of the operational problems reported, the majority involved the inadequate separation of dissolved air flotation (DAF) skimmings and activated sludge bulking. Other problems reported and discussed include poor phosphorus removal and high effluent BOD, total kjeldahl nitrogen (TKN) and ammonia nitrogen (AN) levels. KEYWORDS Poultry Processing, Wastewater, Dissolved Air Flotation, Biological Treatment

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INTRODUCTION As is typical of many food-processing operations, poultry processing is characterized by relatively high usage of water, most of it for non-consumptive purposes (Kroyer, 1991). Typically, poultry slaughter operations produce 5 - 10 gallons of wastewater per bird processed, with concentrations exceeding 2,000 mg/L of biochemical oxygen demand (BOD), 4,000 mg/L of total suspended solids (TSS), and 3,000 mg/L of fats, oil and grease (FOG) (Council for Agricultural Science and Technology, 1995). On June 1, 2001, the National Agricultural Statistics Service (NASS) released the U.S. Poultry Slaughter data for April 2001. The NASS reported that 668,827,000 birds were slaughtered during the one-month period (NASS, 2001). Projected figures based on this data reveal that U.S. poultry processing plants will slaughter over eight billion birds in 2001. Using the typical range of wastewater generated per bird, yearly total wastewater generation by U.S. poultry slaughter plants alone is between 40 and 80 billion gallons annually. Once generated, poultry processors are faced with treating wastewater for ultimate discharge from the plant. Wastewater effluent options include direct and indirect discharge. Direct discharge is defined as the release of wastewater directly into a surface water or land application system. On the other hand, indirect discharge relates to wastewater from the poultry processor that flows to a municipal wastewater treatment facility for further treatment prior to discharge to a surface water or land application system. In general, indirect discharges require less treatment than direct discharges due to further treatment by a municipal wastewater treatment plant. Because of this second treatment step, indirect dischargers are often referred to as ‘pretreatment facilities’. In most cases, regardless of a direct or indirect discharge, the majority of the soluble and particulate organic material in poultry processing wastewater must be removed prior to discharge from the plant in order to achieve compliance with established local, state and/or federal environmental regulations. Depending on the degree of treatment required poultry processors have the option of utilizing physical, chemical and/or biological treatment systems. Each system type possesses unique treatment advantages and operational difficulties. Physical Treatment Physical treatment, in the form of screening, serves a dual purpose in a poultry processing wastewater stream. First, screening recovers offal materials (feathers, viscera, meat particles) that are valuable by-products for the poultry rendering industry. Second, screening prepares wastewater for further treatment by removing the larger solid particles from the waste stream that might otherwise impede the operation and maintenance of downstream equipment and treatment processes. Screening is often the first, simplest and most inexpensive form of treatment. Screens come in various forms (bar, shaker, rotary), and are classified as coarse, which has open spaces greater than 6.0 mm (>0.25 in.), fine, with spaces 1.5 mm to 6.0 mm (0.059 in.– 0.25 in.), very fine, that has gap spaces between 0.2 mm – 1.5 mm (0.008 in. – 0.059 in.) and microscreens, with minute gaps of 1.0 µm – 0.3 mm (3.9 x 10-8 in. – 1.2 x 10-2 in.) (Water Environment Federation, 1998). Screens can be utilized as stand alone units or in series, which

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allows coarser screens to remove larger particles before further screening by finer mesh units. Screens must be sized properly to handle both the hydraulic flow and particle size of the waste stream to prevent ‘blanking’, which is defined as the overload of a screen that results in the coating over of the screen mesh preventing the pass-through of water. Bar screens can be divided into three categories. Trash screens, with openings of 38 mm – 150 mm (1.5 in. – 6 in.) have limited applications in poultry processing facilities. Due to the relativity large openings in trash screens, they are limited to removing only the largest solids within a waste stream. Manually-Cleaned screens have gaps between 30 mm – 50 mm (1.0 in. – 2.0 in.) and Mechanically-Cleaned screens have openings ranging from 6 mm – 38 mm (0.25 in. – 1.5 in.) (Water Environment Federation, 1998). Shaker screens utilize a flat perforated platform that is vibrated at a high speed, allowing solids to be retained on the platform while water flows by gravity through the perforated plate. The most popular form of screens utilized by the poultry processing industry are rotary types. Rotary or drum screens come in two basic forms: internally-fed and externally-fed. In internally-fed rotary screens, wastewater and associated solids are fed inside the drum. Water drains outside the drum while the solids are retained inside. On externally-fed units, wastewater and solids flow over the outside of the drum. The water portion of the stream passes through the drum, while the solids rotate on the outside of the drum and are scraped off on the opposite side of the entry point. Common problems associated with screening include mechanical failures and blanking due either to the overloading of the screen or to under sizing of screen gaps. Chemical Treatment Although there are a variety of chemical wastewater treatment processes available for use in the poultry processing industry, by far the most popular form utilized is dissolved air flotation (DAF). Best described as a physical/chemical treatment, DAF refers to the process of water-solid separation by the introduction of fine gas (usually air) bubbles to the wastewater stream. The microbubbles attach to the solid particles in wastewater causing a solid-gas matrix. The resulting increased buoyancy of the matrix causes it to rise to the surface of the water where it can be collected by mechanical skimming. The use of DAF technology has seen widespread application since the mid-1960’s. The most important aspect of an effectively operating DAF unit is bubble size (Cassell et al., 1975). DAF units produce bubbles that are microscopic in size. Typical DAF bubble size distribution is in the range of 10 µm– 100 µm, which is in the same size diameter range as human hair. Gas bubbles released from a pressurized liquid are not distinguishable to the naked eye. Instead, DAF bubbles give wastewater a milky white (Water Environment Federation, 1998). In addition to the introduction of air, and to increase removal efficiencies, most DAF systems also utilize a variety of flocculent chemicals that aid in the coagulation of the solid materials in the waste stream. Although the skimmed material from DAF units is not as high a quality as screened offal and thus has a reduced value, it is still a viable by-product and is recovered and utilized by the poultry rendering industry. The most common problems associated with operating DAF units are mechanical failures and poor solids separation.

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Biological Treatment Biological treatment or ‘biotreatment’ is defined as the treatment of wastewater by microorganisms in a controlled environment. The microorganisms convert biodegradable, organic particles and some inorganic materials in wastewater into a more stable cellular mass and other by-products that are later removed from the remaining water fraction by physical means, such as settling in clarifiers. Biotreatment methods represent a potentially cost effective approach, requiring little or no chemical inputs, and greater then 90% removal efficiencies of pollutants in poultry processing wastewaters are readily attainable. Typical biotreatment systems include activated sludge systems, lagoons, trickling filters, and septic tanks (Nemerov and Dasgupta, 1991). However, based on information provided by industry experts, biotreatment systems consisting of an anaerobic lagoon followed by an activated sludge system are used by an estimated 25% of U.S. poultry processing plants, and are probably the most common wastewater biotreatment process configuration in the industry (Starkey, 2000). Consequently, the focus of discussion in alternative biotreatment methods in poultry processing operations is principally on anaerobic digestion and activated sludge treatment.

Anaerobic digestion results in the conversion of organic matter into methane and carbon dioxide via a series of interrelated microbial metabolisms under ‘septic’ (no free oxygen present) conditions. Digestion of organic material under these conditions results in the production of a gaseous by-product. This resulting gas mixture, mostly methane and carbon dioxide, with smaller amounts of hydrogen, hydrogen sulfide, and ammonia, is referred to as ‘biogas’.

Given the complex interactions between the various microorganism populations, a number of factors can upset the anaerobic digestion process. Despite potential process instabilities arising from competing biochemical activities, anaerobic digestion has an important advantage over aerobic processes in that power requirements are comparatively minimal since aeration is not necessary for treatment to proceed. However, the low pollutant levels required for the final effluent are typically not achievable anaerobically, hence further treatment under aerobic conditions is usually necessary.

Activated sludge, including its many variations, is probably the most widely used aerobic wastewater treatment process within the poultry processing industry. An activated sludge system consists of two main process units: the aeration basin and the clarifier. The aeration basin provides an environment for the breakdown of soluble and particulate pollutants by microorganisms known collectively as activated sludge. The clarifier provides a quiescent environment that allows the activated sludge solids to separate by flocculation and gravity sedimentation from the treated wastewater.

Solids separation problems in activated sludge systems result in the loss of microbial biomass from the treatment process and eventually lead to process failure. Microbial solids not separated in the clarifier become particulate organic matter carried in the effluent, possibly resulting in non-compliance with treatment objectives for TSS and BOD. Activated sludge system operation, therefore, requires the maintenance of a flocculent, well-settling sludge.

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A number of different solids separation problems have been observed in activated sludge systems, including: (1) dispersed growth, where the sludge does not flocculate; (2) viscous bulking, where large amounts of exocellular slime are produced by the microorganisms; (3) pin floc, where small, compact, relatively weak flocs are formed; (4) filamentous bulking, where filamentous organisms in the sludge flocs extend into the bulk liquid and interfere with settling and compaction; (5) blanket rising, where denitrification releases nitrogen gas which floats the sludge blanket; and (6) foaming/scum formation, caused by non-degradable surfactants or by specific microorganisms (actinomycetes) in the sludge (Jenkins, 1992; Jenkins et al., 1993). Solid separation problems in activated sludge systems are rather common and can be difficult to control. The Council for Agricultural Science and Technology (1995) specifically lists filamentous bulking as a problem in activated sludge treatment of poultry processing wastewaters that must be resolved. Survey Purpose To assist the industry in determining the future focus of scientific and engineering research related to the treatment of poultry processing wastewater, USPOULTRY sponsored an independent University of Georgia Engineering Outreach Program survey aimed at identifying the current practices and experiences of the industry in the area of wastewater treatment. It was determined that the survey should be distributed nationwide and would focus on wastewater treatment. In addition, the survey would investigate how such treatment relates to the type of production and overall plant water use. The survey goals related to wastewater treatment were to determine the extent to which treatment processes are used by the industry, the context in which they are used, problems commonly encountered in their operation, and solutions that have been attempted to control such problems. SURVEY DEVELOPMENT The University of Georgia Engineering Outreach Program and USPOULTRY prepared a seven-page survey, with four pages of supporting figures, for distribution nationwide to the poultry processing industry. The survey was divided into sections on general plant and production information, potable water use and wastewater treatment operations. General plant information included the type of poultry processing operations conducted at the facility, days and hours of operation, number of employees, and shift types. Production information was based on average daily processing levels and asked for the maximum plant design capacity versus actual throughput in each processing area. Survey questions on potable water use asked for total daily plant consumption, percent use by each production/sanitation shift, unit cost and major water consuming processes or pieces of equipment. The most extensive information requested in the survey was in the area of wastewater treatment. General questions included disposal method use for effluent and associated by-products, unit costs and wastewater operation staffing. Surveyed plants described in detail the unit operations utilized to treat their wastewater onsite. Specific information was asked for on the characteristics of the wastewater stream using parameter permit levels versus actual testing results. In addition to permitted parameters, the survey asked for other process control measures used by facilities to ensure proper operation. The residuals resulting from the treatment processes were identified by

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source, generation rate and final beneficial reuse method. Finally, plants were ask to categorize and describe any wastewater treatment operational problems their facility has experienced and what steps were taken to remedy the problem. Utilizing the membership rolls and professional contacts provided by USPOULTRY, blank surveys were distributed nationwide to environmental contact personnel at poultry processing facilities. SURVEY RESULTS Twenty-three poultry processing facilities, located in 11 states, returned completed surveys. Figure 1 shows the location distribution of plants returning completed surveys by state. Surveyed plants were first asked to describe which poultry processing operations are performed at their facility. For the purposes of the survey, poultry processing operations are divided into four categories. First processing (1st) is defined to include the operations of live bird slaughter, cut-up, and chill pack. Second processing (2nd) is inclusive of the operations of deboning, marination, instant quick frozen (IQF), portion control and mechanically separated chicken/mechanically deboned meat (MSC/MDM). Unit operations included in third processing (3rd) are par-fry, fully-cooked, bar-b-que, breading and breading/cook. Finally, rendering, either on-site at a processing facility or as a stand-alone plant, is designated separately from other unit operations. The unit operations performed at the surveyed plants are summarized in Table 1. Figure 1 – Nationwide Distribution of Surveyed Plants

TX 1

PA-1

GA-3

NC- 5

MS-1LA-1

MO1

AR3

DE-3

MD-2

VA-2

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In order of magnitude, the unit operations performed at the surveyed plants were reported as slaughter (83%), cut-up (74%), debone (70%), marination (39%), chill pack (35%), MSC/MDM (22%), portion control (17%), fully-cooked (13%), IQF and breading/cooking (9%). Only one of the surveyed plants reported par-frying and breading. No plants reported bar-b-que as a unit operation. Table 1 – Unit Operations of 23 Surveyed Poultry Processing Plants

Unit Operation Number of Plants Performing Unit

Operation

Percentage of Plants Performing

Unit Operation

1st Processing: Slaughter 19 83

Cut-up 17 74 Chill pack 8 35

2nd Processing: Debone 16 70

Marination 9 39 MSC/MDM 5 22

Portion Control 4 17 IQF 2 9

3rd Processing: Fully-cooked 3 13

Breading/cook 2 9 Par-fry 1 4

Breading 1 4 Bar-b-que 0 0

Rendering 5 22 First Processing Nineteen of the twenty-three surveyed plants encompass slaughtering operations. Of those nineteen slaughtering facilities, thirteen (68%) perform both 1st and 2nd processing operations. Only two plants (11%) are solely 1st operation facilities, and four plants (21%) have 1st, 2nd and rendering operations on-site. Details on plant production levels, processing yields and operational capacities are shown in Table 2. This data shows that the surveyed plants slaughter an average of 169,390 birds or 884,115 live weight pounds of poultry a day, for an average weight per bird of 5.3 pounds. The average output weight of the plants was calculated at 670,964 pounds, for an average yield of 76%. The following assumptions were made in calculating estimated values for unreported data in surveys: average weight of live bird = 5.0 pounds, percent yield from live weight slaughter = 75%.

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Table 2 – Detail of 1st Processing Plants: Average Daily Operations

Plant Number

No. of Birds

Processed

Live Weight (lbs.)

Processed

Avg. Weight per Bird

Weight (lbs)

Output

Percent (%)

Yield

Percent (%) Operational

Capacity

1 160,000 800,000 5.0 600,000 75 nr 2 299,331 1,182,358 4.0 804,003 68 91 3 127,529 990,458 7.8 752,748 76 81 4 134,000 660,000 4.9 552,600 84 100 5 192,000 960,000 5.0 729,600 76 nr 6 172,800 864,000 5.0 648,000 75 nr 7 55,000 275,000 5.0 172,000 63 nr 8 64,400 338,100 5.3 256,956 76 100 9 170,000 1,119,000 6.6 873,000 78 98 10 197,400 1,056,090 5.4 844,872 80 50 11 170,632 853,159 5.0 658,023 77 nr 12 85,316 426,579 5.0 329,011 77 nr 13 260,000 1,114,987 4.4 836,240 75 99 14 265,000 1,457,600 5.5 1,034,000 71 88 15 265,000 1,815,250 6.9 1,422,690 78 99 16 286,000 1,315,600 4.6 1,018,405 77 nr 17 41,000 205,000 5.0 153,750 75 76 18 126,000 630,000 5.0 481,761 76 50 19 147,000 735,000 5.0 580,650 79 nr

Low 41,000 205,000 4.0 153,750 63 50 High 299,331 1,815,250 7.8 1,422,690 84 100

Average 169,390 884,115 5.3 670,964 76 85 nr – not reported Fourteen (74%) of the nineteen first processing plants completing surveys utilize a five day a week, 24-hour work schedule. All of these plants operate two eight-hour production shifts followed by a single sanitation shift. Five plants (26%) reported running only two shifts, one production and one sanitation, over a five-day work week. One plant operates a two-production/one-sanitation shift operation in a four-day workweek. Finally, three (15%) of the nineteen plants reported that they start each workweek off with a separate sanitation shift prior to production startup. The average number of production employees utilized by the surveyed plants is 646, while the average total plant employees were calculated at 758. The lowest number of production and total employees reported is 116 and 152, while the highest employee numbers are listed at 1400 and 1600, respectfully. Potable water use at each facility is reported in Table 3, along with the calculated water use per bird processed. Water use at the plants averages 1.013 million gallons per day (MGD). The average gallon per bird processed range between 4.5 and 8.8, with an average of 6.2.

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Table 3 - Detail of 1st Processing Plants: Average Daily Water Use

Plant Number

Number of Birds

Processed

Water Use (total

gallons)

Water Use (gallons per bird)

1 160,000 1,100,000 6.9 2 299,331 1,400,000 4.7 3 127,529 995,000 7.8 4 134,000 938,000 7.0 5 192,000 900,000 4.7 6 172,800 875,000 5.1 7 55,000 377,000 6.9 8 64,400 424,000 6.6 9 170,000 1,500,000 8.8 10 197,400 987,000 5.0 11 170,632 854,000 5.0 12 85,316 520,000 6.1 13 260,000 1,700,000 6.5 14 265,000 1,200,000 4.5 15 265,000 1,400,000 5.3 16 286,000 2,030,000 7.1 17 41,000 246,000 6.0 18 126,000 1,100,000 8.7 19 147,000 700,000 4.8

Low 41,000 246,000 4.5 High 299,331 2,030,000 8.8

Average 169,390 1,012,947 6.2 Stand Alone Further Processors (3rd Processing) Three completed surveys were received from 3rd or ‘further’ processing facilities. All three of the plants produce fully cooked products. Two plants have breading/cooking operations, and one facility also has breading and par-fry operations. Daily production levels in the plants average 305,000 pounds of product processed by 152 production employees (225 total employees) over a five-day workweek with two production and one sanitation shift. Water use at the three plants averages 150,025 gallons per day. Renderers One completed survey was received from a facility that only renders poultry processing by-products. However, four other surveyed plants perform rendering onsite at facilities doing other operations. Data pertaining to the five operations are expressed in tons and are detailed in Table 4. The one reporting stand-alone rendering plant (plant no. 5 in table 4) operates six days a week with 75 production and 138 total employees on two production and two sanitation shifts. The plant’s average water use is 300,000 gallons per day.

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Table 4 – Renderer Production Levels (Tons Per Day) Plant No.

Offal

(In)

Feathers

(In)

DAF Solids

(In)

Hatchery Waste

(In)

Blood

(In)

Misc. Meat (In)

Oil

(Out)

Poultry Meal (Out)

Feather Meal (Out)

Blood Meal (Out)

1 425 108 23 - 44 - 75 103 36 6 2 95 26 9 - 12 - - - - - 3 28 11 - - - 87 - 50 - - 4 30 30 5 1.2 - - 6 15 15 - 5 1125 400 - - - - 213 297 138 -

Wastewater Permitting & Characteristics All but two of the twenty-three surveyed plants operate their wastewater treatment systems under a local, state or federal discharge permit. Using the total of twenty-one permitted plants, Table 5 summaries the parameters covered by discharge permits. A total of five parameters are required testing for at least 50% of the permitted plants. All of the permitted plants have an established limit for TSS, while over 90% are tested for BOD and pH. Eighty-one percent of plants are tested for FOG, and 57% must meet limits for AN. Wastewater Treatment: Processes In the survey, plants were provided with a table to detail information on the types of wastewater treatment processes utilized. Wastewater treatment processes are divided into physical, physical/chemical, biological, finishing, and final disposal. All of the surveyed plants use some form of treatment on their wastewater. Nine plants (39%) report using a combination of physical, physical/chemical, and biological treatment systems. The remaining plants use one system type alone or two in combination for wastewater treatment. The twenty-three surveyed plants employ a total of 46 state certified wastewater treatment personnel, ranging from zero (at one facility) to five (at two facilities). Thirty-seven additional personnel are employed to assist certified staff. Three plants use only certified personnel with no non-certified assistance, while one plant utilizes only five non-certified staff. Initial physical treatment, in the form of screens are utilized by eighteen (78%) of the facilities. By far the most popular form of screens are rotary types. Of the eighteen plants using screening, eleven (78%) use either internally-fed or externally-fed rotary screens. Two plants use bar screens and two other plants use a combination of rotary and shaker screens. Physical/chemical treatment, in the form of DAF technology, is utilized at nineteen (83%) of the surveyed plants. Plants reported that the solids content of their DAF skimmings range from a low of 11 percent for materials recovered directly from DAF units, to 47 percent for skimmings further treated with dewatering technology such as filter belt presses and driers. Volumes of skimmings produced per day are reported either as pounds or gallons. Daily pounds produced range from 10,000 to 100,000 with an average of 57,000. Plants reporting gallons of DAF skimmings collected ranged from 3,000 to 23,000 with an average output of 8,100.

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Table 5 – Permitted Parameters of Plants by Number and Percentage

Parameter No. of Plants Permitted

% of Plants Permitted

Total Suspended Solids 21 100 Biochemical Oxygen Demand 19 90.5 pH 19 90.5 Fat, Oil & Grease 17 81 Ammonia Nitrogen 12 57 Phosphorus 7 33 Total Kjeldahl Nitrogen 5 24 CBOD 3 14 Chemical Oxygen Demand 2 9.5 Nitrate / Nitrite 2 9.5 Total Residual Chlorine 2 9.5 Organic Nitrogen 1 5 Chloride 1 5 Sodium 1 5 Dissolved Oxygen 1 5 Total Nitrogen 1 5 Fecal Coliform 1 5 Enterococcus 1 5

Biological treatment is divided into anaerobic digestion, activated sludge, aerated lagoon and facultative (non-aerated) lagoon. The most popular form of biological treatment among the surveyed plants is activated sludge with ten facilities (43%) reporting the use of extended air, oxidation ditch or biological nutrient removal (BNR) technologies. Overall capacities of activated sludge systems ranged from 400,000 to 13 million gallons with the average system capacity of 3.35 million gallons. Aerated lagoons were the second most popular type of biotreatment with eight (35%) of plants reporting their use. Ponds ranged in size from 1.2 to 7.0 acres and capacities from 975,000 to 14 million gallons. Three plants (13%) report the use of anaerobic digestion, while three plants use facultative lagoon as part of their biotreament system. Finishing treatment of wastewater is divided into final clarifiers, filtration, polishing ponds and disinfection. Eleven plants (48%) use final clarifiers ranging in capacity from 296,000 to 1.27 million gallons. Only one plant utilizes a combination of ‘rough’ followed by ‘polishing’ filtration, while only two plants have final polishing ponds. Eleven plants (48%) have disinfection systems associated with their wastewater treatment. Eight plants use chlorine gas, two use sodium hypochlorite, and one plant uses a UV (ultraviolet light) system for disinfection. Final disposal of treated wastewater or ‘effluent’ is divided into two basic categories: direct discharge (to surface water and/or land application) or indirect discharge (to municipal sewer system). Thirteen plants (57%) reported themselves as direct discharges. Eight of the thirteen plants use land application systems, three facilities use a combination of land application and surface water discharge, while two plants release all of their treated effluent to a surface water. Ten (43%) of the facilities pretreat their waste streams prior to discharge to a municipal sewer system for further treatment.

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Wastewater Treatment: Process Control Measures Surveyed plants were asked to list the operating parameters that are regularly monitored and/or controlled to ensure proper wastewater treatment plant operation. Along with permitted parameters, these tests are used to diagnose operational problems. A number of typical process control measures were listed for surveyed plants and blanks provided for additional entries. For each parameter, plants were requested to note sample point and frequency of testing, target testing level, and if monitoring and/or control of parameter is automated. A prioritized summary of plant responses showing control measures used at a minimum of two facilities is presented in Table 6. Table 6 – Process Control Measures: Number and Percentage of Plants Parameter*

Sample Point

Frequency#

No. of Plants

% of Plants

Target Levels (Range)

No. of Auto.

Monitoring

No. of Auto.

Control

DO Aeration C,H,D,W 12 52 1.0 – 6.0 mg/L 4 4 pH Aeration C,H,D,W 12 52 6.0 – 9.0 S.U. 4 4 pH DAF C,H,D,W 11 48 4.2 – 7.4 S.U. 8 7 Chlorine Effluent H,D 10 43 <1.0 – 2.5 mg/L 1 0 MLSS Aeration D 9 39 2K – 5K mg/L 1 0 AN Clarifier D,W 9 39 <1.0 – 28 mg/L 1 0 COD DAF Eff D,W,M 7 30 160 – 800 mg/L 0 0 SVI Clarifier D,W 6 26 80 – 150 ??? 0 0 Nitrate Clarifier D,W 5 22 <5 - <75 mg/L 0 0 Alkalinity Clarifier D,M 4 17 50 - >350 mg/L 0 0 pH Digester W 3 13 7.0 – 7.2 S.U. 0 0 * DO – Dissolved Oxygen, MLSS – Mixed Liquor Suspended Solids, AH – Ammonia Nitrogen, COD – Chemical Oxygen Demand, SVI – Sludge Volume Index # C – Continuous, H – Hourly, D – Daily, W- Weekly, M - Monthly Wastewater Treatment: Residuals The survey asked each respondent to list the residuals created by the operation of their wastewater treatment systems. Categories provided include screenings, DAF skimmings and waste activated sludge. Of the fifteen plants reporting the recovery of screened materials, fourteen (93%) pass the by-product along to a rendering operation. One plant reports that their screenings are land applied. The rendering industry also handles the vast majority of DAF skimmings, thirteen (72%) of eighteen reporting facilities, with the remaining five plants using land application systems. Finally, plants utilizing aeration systems were asked about their waste activated sludge. Of the nine reporting plants, six use land application and three use anaerobic digestion to handle the by-product.

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WASTEWATER TREATMENT OPERATIONAL PROBLEMS Of the twenty-three plants returning completed surveys, thirteen (57%) reported fifteen specific wastewater treatment operational problems. The problems are summarized in order of number of incidents in Table 8. The poor separation of DAF solids in physical/chemical treatment systems is the problem experienced the most by the surveyed plants. Of the five plants reporting problems with DAF solids, only two offered a suspected cause. One plant traced the problem to low pH in the potable water supply, while the other plant had an accidental spill of blood to the waste stream. Three of the five plants addressed the problem with chemical addition, one plant complete maintenance on their system, while one addressed the problem of low pH with the municipal water supplier. Activated sludge bulking was the second most experienced operational problem of the surveyed plants. Three plants reported the problem, with suspected causes listed as filamentous and spring turnover. Remedies included chlorinating and increasing the return activated sludge (RAS) flow, and increasing aeration levels. Table 8 – Wastewater Treatment Operational Problems Problem

Suspected Cause Remedy

Poor DAF Solids Separation

1. Potable water supply pH too low (<7.0 S.U.) 2. nr 3. nr 4. Accidental blood dump 5. nr

1. Formal request to public water supplier to maintain pH of 7.2 S.U. 2. Use of new GRAS polymers 3. Check and blow out air supply nozzles 4. Slow DAF feed, increase floc agent 5. Jar tests conducted, new polymer in use

Activated Sludge Bulking

1. Filamentous 2. nr 3. Spring turnover

1. Chlorinate RAS 2. Increase RAS, maintain minimum DO in oxidation ditch 3. Increase aeration & apply coagulant

Poor Phosphorus Removal

1. nr 2. No phosphorus removal designed in present system

1. Change from Alum to liquid Sodium Aluminate 2. Evaluating new technology

High Effluent BOD Levels 1. Sugars from marinades and glazes 2. nr

1. Increase chemical dosage and retention times 2. Increase aeration/DO levels

High Effluent AN Levels nr Reduced system flow to increase detention times

High Effluent TKN Levels nr Evaluating alternative treatment options

Cloudy Effluent Overfeeding Hydroxide Magnesium

Reduce feed to proper level

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REFERENCES Cassell, E.A., et al. (1975). The Effects of Bubble Size on Microflotation. Water Resources. Vol. 9, p. 1017.

Council for Agricultural Science and Technology (1995). Waste Management and Utilization in Food Production and Processing. Task Force Report No. 124. CAST, Ames, IA.

Jenkins D. (1992). Towards a Comprehensive Model of Activated Sludge Bulking and Foaming. Water Science and Technology, Vol. 25, No. 6, pp. 215-230.

Jenkins D., Richard M.G. and Daigger G.T. (1993). Manual on the Causes and Control of Activated Sludge Bulking and Foaming. CRC Press, Boca Raton, FL.

Kroyer G. Th. (1991). Food Processing Wastes. In: Bioconversion of Waste Materials to Industrial Products, Martin A.M., Ed. Elsevier Applied Science, NY, NY, pp. 293-311.

National Agricultural Statistics Service (2001). Poultry Slaughter. NASS Report No. Pou 2-1 (06-01). Agricultural Statistics Board, U.S. Department of Agriculture, Washington, D.C.

Nemerov N.L. and Dasgupta A. (1991). Industrial and Hazardous Waste Treatment. Van Nostrand Reinhold, New York, NY.

Starkey J. (2000). Vice President for Environmental Programs, U.S. Poultry & Egg Association, Tucker, GA. Personal Communication.

Water Environment Federation (1998). In: Design of Municipal Wastewater Treatment Plants, Volume 2 & 3, WEF Manual of Practice No. 8, 4th Edition, Alexandria, VA.