The treatment plant, In fOrQgrOUnd, blends In wkh the rest of the HlllShlre Farm complex.

ComDonent mix meets ATP tough standards ~ : N x ~ ~ ~ ~ ~ ~ ~ ~ large This WWTP's volumes unusual of high-strength equipment industrial combination waste water treats -

I By Neil A. Van Dyke, P.E.

COMPONENTS NORMALLY USED for secondary level treatment achieve tertiary level efficiencies and meet discharge permit requirements in han- dling up to 1 mgd of high-strength, high-temperature, wastewater from the Hillshire Farms meat packing and ren- dering operations.

Hillshire Farm Company of New London, Wisc., is a nationally known producer of natural casing sausages with an output of 4 million pounds of meat products per week. Slaughtering and manufacturing operations expanded substantially since the original treatment plant was built in 1973. A work force of Van Dyke is an associate with Foth & Van Dyke and Assoc., Inc.

36 I WATER & WASTES ENGINEERING

200 employoes mushroomed to over 1,100 people.

Hillshire's expansion plans included a multi-million dollar rendering facility capable of converting the normal wastes of bones and meat scraps into usable by-products such as gels and protein supplements. It would be one of the first installations of its kind in the United States. Its by-products would be used by the pharmaceutical and pho- tographic industries.

The rendering wastes were expected to have a BODS of up to 10,000 mg/l, extremely high amounts of oil and fats, and a temperature range up to 185OF. The existing treatment plant needed to be upgraded from a capacity of 375,000 gpd (2300 Ibs/BOD5/day) to 1 mgd

(10,770 Ibs/BOD5/day) for the proposed expansions. The waste strength to be treated was the equivalent of a city of 64,000 people.

To solve this treatment problem plant designers, Foth & Van Dyke arid Assoc., Inc. of Green Bay, Wisc., obtained waste sample from a similar rendering process in Australia. Laboratory treat- ability studies led to the specific adap- tation of the treatment units able to in- corporate the rendering wastes into the process wastewater treatment flow.

A cost effective and innovative combination of dissolved air flotation, modified activated sludge, and bio-oxi- dation tower components enabled Hill- shire Farm to expand its prcduction capabilities at its own pace. This ex-

Flow diagram

pansion has coincided with the treat- ment facility expansion in compliance with strict existing discharge limitations as well as those proposed by EPA for 1983.

The unusual design features of the expanded treatment facility include:

Dissolved Air Flotation Units: Used for by-product recovery and an in- tegral part of the treatment proces- s-as primary treatment and oil and grease removal Bio-Oxidation Tower: Pretreatment of high strength and high tempera- ture rendering wastes while con- serving energy and space

a Incorporation of Treatment Com- ponents: Bio-tower and other sec- ondary treatment units combined to provide tertiary treatment at sec- ondary treatment costs

0 Aeration Basin: Lightly reinforced sloped slab-on-grade construction with center diffused aeration system reduced construction costs and time Superior Treatment Performance: Tertiary level effluent consistently produced at and above design flows

a Marsh Vegetation Treatment: Ad- ditional BOD and SS removal ob-

tained through man-made marsh system, provides buffering zone prior to stream discharge should a treatment plant breakdown or upset occur.

Environment must be protected One of the foremost considerations

was to design a treatment facility that would comply with all state and federal environmental regulations as well as adequately address local public concerns.

The existing treatment plant had been discharging into a small drainage course at its required secondary treatment level (30 mg/l BOD and SS) since its com- pletion in 1973. This stream passes near numerous residences and fxms prior to discharging into the Wolf River, a popular recreational resource.

With the ever increasing sensitivity to the protection of natural resources, the proposed limits for the expanded facility were made more stringent in order to preserve the area’s high water quality, (Table I). These revised pa- rameters, coupled with the increased wastewater load, dictated a facility de- sign that could treat a much higher strength waste to much more stringent effluent requirements than had been previously required.

The completed project has compiled with, as well as exceeded, state and federal environmental regulations. The expanded treatment plant discharges a high quality effluent to area water- cours,es. This high degree of treatment preserves the surface and groundwater resources of the area.

During design investigation, Foth & Van Dyke considered pumping the ef- fluent directly from the expanded facility approximately two miles to the Wolf River where it was anticipated that the discharge limits would remain at the secondary level.

Regulatory agencies objected to this alternate discharge to the Wolf River citing possible destruction of walleye pike spawning beds located in the vi- cinity of the proposed discharge point.

NOVEMBER 1980 [ 37

Expansion included another aeration basin and the bio-oxidation tower and dissolved air flotation building seen in the background.

As a result, the carefully monitored ef- fluent continues to be discharged to the small environmentally sensitive stream near the plant.

The superior performance of this new treatment system is shown in Table 2 which lists effluent characteristics over two recent months of operation, as compared to the requirements of the discharge permit. In many cases the effluent exceeds requirements by 300 % . These levels of treatment have been maintained at, and above, the 1 mgd design flow of the plant.

Aesthetics also considered Another key design requirement was

to produce a facility that would be compatible with the high sanitation standards typical of a food processing plant. This was particularly important since the treatment plant is not located in a remote or sheltered area. but is an

integral component of the entire pro- cessing operation. The facility needed to be aesthetically pleasing and odor- free. Hillshire Farms promotes a fa- vorable public image and enjoys its “good neighbor” status with the City of New London. This good neighbor status is especially important since the Hill- shire Farm facility is in a highly visible site on the fringe of the city and sur- rounding residential areas.

All structures included in the treat- ment facility expansion had to be com- patible with the existing treatment plant components and blend with the overall processing plant scheme. The treat- ment facility therefore is indistinguish- able from the bulk of the process plant to the casual observer and does not detract from the well kept appearance of the entire Hillshire Farm Company operation. Tours of the Hillshire facility include the treatment plant as a stop.

A rigorous schedule of laboratory treatability testing was required to colncido the treatment expansion with the new rendering facility construction.

The expansion of the meat packing operation, specifically the addition of the rendering process, would produce a very high strength, high temperature, wastewater. The rendering wastes were estimated to contribute almost cne half of the total BOD load to the plant while constituting only 6 % of the total flow. There was concern over the possible effect this waste stream would have on the existing, as well as the proposed, treatment plant components.

Also important was the fact that the rendering facility, as well as the packing plant, did not operate on the weekends. This coupled with the highly variable organic loads coming from these facil- ities at any given time, demanded a treatment system which would be al- most totally “shock” resistant while retaining low flow treatment capability.

To complete treatability studies on the rendering wastewater, ,it was nec- essary to obtain samples of a typical discharge and evaluate biological, chemical, and mechanical means of treatment. The closest source o i these samples was from an Australian oper- ation. Consequently, the samp!es had to ,be refrigerated and flown half-way around the world to Foth & Van Dyke’s laboratory where dissolved air flotation tests were performed on the wastewa- ter to determine fat, oil, and grease re- moval efficiencies as well as BOD and SS removal.

Three alternate methods of incor- porating these high strength and high temperature rendering wastes into the treatment system were determined. 0 Treat the rendering wastes com-

pletely separate from the normal process wastewater.

0 Add the rendering wastes directly into the modified activated sludge treatment system.

0 Pretreat the rendering wastes to

38 1 WATER & WASTES ENGINEERING

*' * more compatible levels prior to - mixtng into the activated sludge system.

Pretreat and blend wastes After much study it was decided to

pretreat the rendering wastes to lower strength and temperature levels prior to mixing with the normal process waste- waters so these wastes would be more amenable to treatment by the modified activated sludge process.

After evaluating two installations in Idaho which use the activated bio-filter process on potato processing and mu- nicipal wastes, it was felt that this pro- cess would be very applicable to the Hillshire Farm situation. The process uses redwood slat-type media in a bio- oxidation tower. A mixture of waste- water and activated sludge is distributed over the media for treatment. The bio- filter process provided numerous benefits

0 Substantial energy savings over equivalent BOD removals using conventional aeration basins were achieved.

0 The cooling capabilities of the tower helped reduce the high temperature (185OF) of the ren- dering wastes to a more com- patible level. A portion of the normal process wastewater is diverted to the bio-tower wet well where it is mixed with the ren- dering wastes and return acti- vated sludge. This mixture is then pumped over 21 ft. of redwood media achieving cooling as well as oxygen transfer and BOD re- duction prior to discharging into the modified activated sludge system.

0 The system can handle shock organic and pH loads.

0 It reduced the amount of space required for the treatment plant expansion by approximately one half acre of very valuable property.

The treatment system now handles highly variable waste loads during the week and little or no flow during the weekends with no plant upsets and continued superior treatment results.

Hillshire Farms required a very tight construction schedule which coincided completion of the treatment facilities with the process plant expansions and specifically the rendering unit addition.

The rendering installation production of marketable by-products justified the extremely large capital investment. Failure to meet the tight time schedule would result in a $3 million process standing idle with no payback.

Construction and modification of the treatment plant had to be completed

'

while maintaining the required degree of treatment for the existing process wastewater. No interruptions of this service could be tolerated.

Construction of the treatment facili- ties began approximately seven months after the start of treatability studies. The plant became fully operational in Jan. 1979.

Construction of the new facilities did not interfere with the existing treatment process or interrupt the normal opera- tion of the meat processing operation and allowed the rendering process to be placed on line as scheduled.

Capital and O&M costs studied As would be expected, the system

had to be designed within budgeted amounts and have the lowest operation and maintenance costs possible.

Because the 1973 treatment plant successfully treated the Hillshire Farm Company wastewater, there was a natural tendency to play it safe and ex- pand the plant by adding units identical to those already in use. This would have resulted in the addition of extremely large aeration basins with associated large aeration diffuser and blower equipment. The annual cost of electrical power for these blowers would have been prohibitively high.

Alternative treatment methods were analyzed to minimize the capital ex- penditure needed for the treatment plant expansion as well as to provide for the best possible treatment with minimum energy consumption. Also considered

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was the potential for redaiming mar- ketable by-products to help further re- duce annual costs.

The treatment facility fulfilled all of the client's considerations and has maintained its superior treatment on a daily and monthly basis. The project construction cost of $950,000 was ap- proximately $50,000 less than the budgeted amount (Table 3). This can be attributed to the design and to some of the construction techniques used.

The bio-oxidation tower saves ap- proximately 200 horsepower as com- pared to blowers for the diffused aera- tion system. This power savings trans- lates into an annual savings of ap- proximately $31,000 at current electric rates and will, of course, become greater in the future as cost of electricity increases.

In reference to the recovery of mar- ketable by-products from the treatment process itself, much flexibility is de- signed into the plant to enable fats, oils, greases, and/or waste sludges tCJ be reclaimed as the market dicta;es. Presently waste activated sludge from the facility is dewatered and used as a soil conditioner on the adjacent tarm- lands. n o

NOVEMBER 1980 I 39