LOW OPERATING COST WASTEWATER TREATMENT TECHNOLOGIES FOR RED MEAT AND OTHER INDUSTRIES

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1 LOW OPERATING COST WASTEWATER TREATMENT TECHNOLOGIES FOR RED MEAT AND OTHER INDUSTRIES Mitchell Laginestra 1 1. GHD Pty Ltd, Adelaide, SA ABSTRACT The cost of treating wastewater from red meat processing and other high organic wastewaters is increasing with more stringent environmental discharge requirements and rising power costs. Red meat wastewater contains high concentrations of contaminants which necessitates a multiple treatment processes to meet environmental quality criteria. A typical treatment system for the industry involves anaerobic process followed by aerated lagoon or activated sludge variants to provide suitable effluent quality. The two key shortcomings of the systems involve footprint and high power and annual costs. While capital cost is a main driver, more simple processes with lower annual operational costs are seen as significantly advantageous. The focus of this paper is the advent of anaerobic lagoons and trickling filtration process. Although regarded by some critics as low technology or outdated, these processes have the ability to minimise capital and annual costs, and reduce greenhouse gas emissions. The paper includes a presentation of criteria and reviews technology applications for the industry and presents a cost comparison. INTRODUCTION The cost of treating wastewater from red meat processing and other high organic wastewaters is increasing with environmental discharge requirements and rising power costs. Red meat wastewater has high contaminant concentrations (refer Table 1), typically loaded with solids, floatable matter (fat), blood, manure and a variety of organic compounds and which necessitates a multiple process treatment train. A typical treatment system involves anaerobic systems (long detention time but minimal operating costs) followed by activated sludge variants (relatively short detention time, but high power cost system) to provide suitable effluent quality. While capital cost is a key driver, more simple processes with lower annual operational costs are seen as significantly advantageous by operators. To that end, covered anaerobic lagoons and trickling filtration are regarded as appropriate for meat industry wastewater treatment. Although regarded by some critics as low technology or outdated, these processes have the ability to minimise capital and annual costs, while at the same time generating energy and reducing greenhouse gas emissions respectively. REVIEW OF TECHNOLOGIES There are a number of technologies that are applied to wastewater treatment at meat processing plants. Treatment typically involves a multiple process train: Physical or primary treatment for solids and grease removal, typically involving Dissolved Air Flotation (DAF), and screening; Biological or secondary treatment to reduce the bulk of the BOD comprising: o Anaerobic digestion (lagoons are most common in USA and Australia, but constructed reactors have also been used, although mainly in Europe) o Aerobic treatment downstream of anaerobic systems typically activated sludge, waste stabilisation ponds or aerated lagoons. Anaerobic treatment is popular as a first stage of biological treatment of abattoir wastewater and considered to be well suited to abattoir wastewater. It is noted that lagoons are more popular in the USA and Australia, since climate conditions and land availability allow the construction of large lagoons. However, many are uncovered (due to cost limitations). Covering of these lagoons provides a number of benefits, such as: Opportunity to control odours. Capture of greenhouse gases. Ability to use biogas to generate electrical energy and thus minimise the carbon footprint of the facility. Downstream of anaerobic ponds, aerobic systems are required to control odours and reduce BOD to acceptable levels and so enable environmental discharge. In most countries ponds remain the most common form of aerobic treatment for removal of COD from wastewater. However, a wide array of mechanical systems, including activated sludge systems (more common) and trickling filters have been used. The main advantage of the pond systems is their simplicity to build and operate, although their nonmechanical aspect means a greater volume (and subsequently area / footprint) is required to treat

2 wastewater than conventional (mechanical) treatment systems. Over the past 30 + years, trickling filters have largely been replaced by activated sludge processes in municipal and industrial wastewater treatment. Although involving significantly lower running costs and operational simplicity compared to activated sludge systems, they are often regarded as old technology. However, the advent of plastic support media in lieu of older stone type, has allowed increased height and loading capability and enhanced ability to nitrify, which could change perceptions. DESIGN CONSIDERATIONS TF VERSUS AS It should be noted that while activated sludge is the most widely used secondary biological treatment system for most wastewaters around the world, key drawbacks are the potential for sludge bulking, excess sludge production and demanding operations and maintenance requirements (particularly where load is constantly changing, as in processing days in industrial applications). Advantages of trickling filters are the low energy usage compared to activated sludge, as well as reduced complexity and sludge production. In addition, fixed film systems (TF s) are less susceptible to toxicity and shock loads than activated sludge systems. Trickling filters have traditionally taken up more land. With the high rate plastic media trickling filter process, this is no longer the case. Because of the high concentration of biomass attached to the media surface area, the reactors can handle higher loads per unit volume than activated sludge. Effluent quality is not regarded to be equal to that of the conventional activated sludge process, however, trickling filtration can provide a very good effluent quality and the process is capable of significant removal of pollutants (including COD, ammonia-nitrogen, oil and grease). In addition, if total nitrogen reduction was required then some activated sludge system may be applicable downstream of the trickling filter. Combined systems provide a robust process, with minimised energy use and enhanced effluent quality, and have been adopted at a number of municipal and industrial applications in Australia and USA. In these cases, typically the trickling filter reduces the operating costs, and acts as the main organic treatment unit, while the activated sludge system (with vastly reduced aeration requirements) acts to reduce nitrogen (via nitrification and denitrification processes) and polish the effluent for environmental discharge. Trickling filters require primary treatment for removal of settleable solids and oil / grease (to a greater extent than activated sludge systems) to prevent accumulation and / or excessive growth which can lead to system blockage. In addition, for high-strength industrial wastewaters, recycle of effluent (recirculation) is usually practised. In the red meat industry, DAF and anaerobic digestion are typically employed. Both are capable of reducing high solids and fats, and consequently are regarded as appropriate prior to trickling filters. POTENTIAL ISSUES OF LAGOONS AND TF S While advocating particular processes, it should be noted that all sites have their own specific aspect and potential issues, and a review of these is regarded as essential in development of the design. Potential issues with covered lagoons include: Failure to achieve required organic reduction (overloading, leading to low gas production and potential failure); Scum accumulation (and interference with flow paths); Need for periodic sludge removal (and difficulty in removal of covers). Improperly designed trickling filters can have a number of issues, including: Failure to achieve required organic / nitrogen reduction; Odour generation; Filter flies; Clogging and ponding of filter media; Clogging of distributor nozzles; Media collapse. It should, however, be noted that appropriate design (particularly in regards to loading) and flexibility in the process can overcome most of these issues. For lagoons, surface feed nozzles to break up scum, and incorporation of internal sludge recycling (with valved removal) to avoid the necessity to remove the cover may be appropriate. On a general note, for treatment by trickling filtration, it is considered that there are risks of: excess BOD / COD, leading to development of anaerobic conditions in the trickling filter, and resultant odours; Fat and grease build up, which may increase within the trickling filter (with cooling) if not previously removed. Again this will lead to odour generation. Application of trickling filtration after anaerobic ponding might be suitable, (since BOD and fats have been reduced). However, presence of solids, ammonia and dissolved sulphides may result in blocking and stripping of odours respectively. Effective design will be required to ensure the use of the technology is employed appropriately. LITERATURE SURVEY CASE STUDIES

3 General Although there are numerous applications of covered anaerobic lagoons in the industry, the use of the generated biogas is rare, due to the cost of implementation of cogeneration systems. It is noted, trickling filters are not typically adopted for treatment of abattoir waste, despite lower operating costs. Achievement of low BOD effluent and nitrification can provide ideal conditions for proliferation of fly larvae (which may be unacceptable in the vicinity of the abattoir). High nitrogen loadings of abattoir wastewater may also be an issue. Consequently there are no greenfield sites that the author is aware of, in which a cost comparison may be undertaken. However, trickling filtration has been installed at a chicken processing plant as an adjunct to an activated sludge system to minimise operating costs. Other case applications Early work in the 1970 s noted that experience with meat wastes with trickling filters proved unsatisfactory. However, this remark related to stone media TF s, and only limited pre-treatment was applied. It was noted that high protein content of the wastewater led to heavy biological growth resulting in clogging. The advent of plastic media with the open structure has undoubtedly reduced the tendency to clog and provides improved oxygenation. In the early 1980 s some 3 high rate (plastic media) trickling filter processes were reported (Laginestra 2015) as being installed at 3 Australian abattoirs (not named). TF s were noted to be particularly suitable for partial treatment or as a roughing process due to operational simplicity, low operating costs and resistance to shock loads. Nearly all known TF applications constructed within the last 25 years involve plastic media trickling filters (although in developing countries stone trickling filters are still built). The only known current red meat industry application of trickling filters is reportedly at an abattoir in Corio (Victoria). It is understood that it is used as a roughing system prior to sewer discharge and it performs satisfactorily. Johns (1995) states that high rate trickling filters have been successfully used as roughing filters in Europe to achieve preliminary BOD reduction in rendering and abattoir wastewaters. Key advantages are their low space and energy requirements. Good fat removal is required to prevent coating of surfaces of the TF media. It was also noted that this technology has not been widely adopted by US or Australian abattoirs, although its suitability has been demonstrated. Nutrient removal plants, based on an activated sludge biological nitrogen reduction system have been developed where significant nitrogen reduction is required. Abattoir wastewater contains a high concentration of nitrogen, which typically requires some reduction, even with irrigation of pasture land. No nitrifying TF systems for abattoirs have been reported. The major issue is reportedly lack of denitrification capability. However a number of nitrifying and denitrifying filters have been developed since the 1990 s in other industries. Other sources cite numerous trickling filter applications in the USA, with various loading rates kg BOD / m 3.d with BOD removal rate ranging from % (Laginestra 2015). Overview There is a general indication that with appropriate pre-treatment, trickling filters could work in the red meat industry (and have operated at tanneries, dairies and chicken processing plants), but a possible pilot plant to determine loading rates would be required. There are numerous applications for high BOD wastes being treated by trickling filter technology overseas including: Canning operations TF s preferred due to ease of maintenance, possibility of shock loads and weekend shut downs; Bakery wastewater (Wang et al 2006) - rock media TF demonstrated significant reduction in oil / grease from 1500 mg/l to 30 mg/l; Vegetable wastewater - polyurethane TF media (high specific surface area 256 m 2 /m 3 ). Plant downstream of anaerobic treatment, achieved 82 % nitrification at loadings of < 1.4 kg COD/m 3.d (only 20 % at 3 kg COD/m 3.d). Australian / New Zealand TF applications, most of which are years old, include: Nestle Tongala dairy processing plant (now Fonterra); TF used as a roughing filter prior to BNR plant, Joe White Malting in Perth [although now understood to have been replaced by MBR]; In New Zealand, a trickling filter was installed at a chicken processing plant in combination with AS system; Soft drink manufacturer, Huntingwood (Sydney) roughing filter for activated sludge; Pesticide manufacturing plant (north of Sydney) uses an activated carbon trickling filter downstream of activated carbon system to cater for high COD, prior to SBR system. It is interesting to note that all the above applications comprise a combined / hybrid system with activated sludge. The AS was introduced to cater for nutrients and enhance effluent quality in a number of systems, while the TF technology was adopted to either cater for peak organic loads or minimise aeration costs.

4 DESIGN OF COVERED ANAEROBIC LAGOON SYSTEMS While there are a number of broad design parameters, recommended features for abattoir anaerobic ponds in Australia include Loading rate of kg BOD/m 3.day. Hydraulic retention time of 10 to 40 days. Depth of 3 to 5 metres. Length to breadth ratio of 3:1. Cover thickness of minimum 2 mm. Allowances for removal of fat / sludge. DESIGN OF TRICKLING FILTERS General There are a number of factors in design of trickling filtration systems. Maintaining loading to adequately reduce BOD / COD, with or without nitrification, as well as avoid nuisance vectors such as odours and filter flies, with plastic media an organic loading rate of somewhere between 0.6 to 1.6 kg BOD/m 3.d would be suitable, with recirculation. Irrigation to maintain wetness of the media (~ 50 m 3 /m 2.d) is also important, as is depth. It is noted that plastic media filters are limited to about 6 metres height without forced ventilation, but may be constructed up to 10 m with forced draught air supply. Pilot Trial While application of anaerobic systems is well documented for the red meat industry (rather the current inhibitions are related to cost of covering and use of the biogas), trickling filtration is somewhat unknown in the modern industry. Based on the literature review, broad areas for trickling filtration design (and applicability to the red meat industry) that might be considered as part of a trial and / or research program could include the following: Irrigation rate dependent on media type. Odour generation - particularly where located downstream of anaerobic ponds. Organic loading dependent on requirements for nitrification. Grease concentration and pre-treatment requirements. Effluent quality capability achieving appropriate quality of treated water. Cost / Benefit analysis energy efficiency, cost of media, savings for energy, operations etc. LOW COST TREATMENT Treatment train Red meat processing wastewater requires multiple treatment units to achieve the required effluent quality. There is no panacea and requirements will be governed by site specific aspects. However, if we consider a rural location, where only low nitrogen reduction is required, then to achieve energy efficiency and cost effective design, a broad general process train, might involve: Screening and dissolved air flotation (DAF), Anaerobic lagoon, Trickling filtration and humus settling tank, Maturation ponding. However, where significant nitrogen reduction is required, the above treatment train could be augmented by incorporating an aerobic (reduced aeration) / anoxic zoned biological system downstream of the trickling filter to achieve enhanced nitrification and denitrification. A larger secondary clarifier would also be required instead of the humus settling tank. Cost comparison Generalisation of cost estimates for typical systems is difficult as a large component of costing is site specific and the requirements, opportunities and constraints of each system vary considerably. The costing can be split into construction/capital, ongoing/maintenance costs and potential benefits/repayments. In considering payback for a treatment system, there are a large number of variables, including: Implementation of necessary pre-treatment. Size of lagoon and earthworks required. Size of TF and type of media Extent of recirculation required Influent quality. Biogas quantity. Use of biogas. Price of electricity. For enabling comparison, I have prepared a comparison of systems (as outlined below and contained in Table 2). In this investigation, I have considered the potential costs of three different systems. Costs are indicative only, but are regarded as relative, since many factors influence the final costs. The comparative review involves a red meat abattoir, generating wastewater flow of 1.5 ML/day (medium size abattoir). I have assumed the treatment train is downstream of an existing DAF system and that there is a need for nitrogen reduction. The three options are: Uncovered anaerobic lagoon, followed by activated sludge system; Constructed digester, followed by activated sludge system, involving biogas collection and conversion to electrical and thermal energy; Covered lagoon, followed by hybrid trickling filter, activated sludge system, involving biogas collection and conversion to electrical and thermal energy (refer schematic diagram Figure 2).

5 Annual costs include operations / maintenance, electricity and sludge management (and potential benefit of gas generation where applicable). A nett present cost was calculated using 5 % discount factor over 20 years. The comparative review indicated a significant advantage to the covered anaerobic lagoon, hybrid TF / AS system, with payback after 7 years, and 13 % saving in nett present cost, compared to the base case. CONCLUSIONS Treatment of red meat processing wastewater requires a process train comprising multiple treatment units. A balance between reduced operating costs (enhanced energy efficiency) and environmentally appropriate treatment to achieve required effluent quality criteria is important to maintain sustainability of the industry. The energy usage associated with red meat wastewater is typically associated with aeration and sludge management as a result of treatment. Covered anaerobic lagoons generate energy and produce minimal sludge, while trickling filters use less energy (some %) and produce less sludge (approx. 15%) than mechanically aerated systems. Covered anaerobic lagoons are entirely practical for the meat industry. Biogas use is appropriate, and while costs of cogeneration are high, payback is achieved within a few years. The activated sludge process (or aerated lagoon system) has generally overshadowed the older technology trickling filter on the basis of effluent quality and operational control aspects. Trickling filters have not been considered for any municipal upgrades for many years, and activated sludge is certainly more popular to achieve nutrient removal requirements. Pre-treatment is generally regarded as critical for TF systems (more so than activated sludge). Both processes are located downstream of anaerobic lagoons in the red meat industry to achieve low BOD in the final effluent. ACKNOWLEDGEMENTS The funding of the two studies which form the basis of this paper by MLA and AMPC is gratefully acknowledged. REFERENCES Daigger, G.T. & Boltz, J.P. (2011) Trickling Filter and Trickling Filter Suspended Growth Process Design and Operation: A State-of-the- Art Review. Water Environment Research, Vol. 83, 5 pp Johns, M. R. (1995) Developments in Wastewater Treatment in the Meat Processing Industry: A Review. Bioresource Technology, 54, Laginestra, M (2012) Report on Covered Anaerobic Lagoons Review of Design and Operational Aspects for Red Meat Industry Applications. Report A.ENV.0135 for Meat and Livestock Australia and the Australian Meat Processor Corporation. Laginestra (2015) Trickling Filter Technolgy for Treating Abattoir wastewater, AMPC report 2014 / 1016 Wang, L.K., Hung, Y., Lo, H.H. & Yapijakis, C. (ed.) (2006) Waste Treatment in the Food Processing Industry, CRS Press (Boca Raton, USA). Zahid, W.M. (2007) Cost Analysis of Trickling Filtration and Activated Sludge Plants for the Treatment of Municipal Wastewater. P proceedings of the 7th Saudi Engineering Conference, College of Engineering, King Saud University, Riyadh, 2-5 Dec. Trickling filtration is a simple to operate process with ability to achieve low BOD and ammonia. Dependent on environmental discharge criteria, it may be suitable downstream of an anaerobic lagoon, and to provide suitable effluent quality as a standalone downstream process. Alternatively, where total nitrogen reduction is required, to enable minimal operating costs, a hybrid system may be appropriate, which involves: Trickling filter in conjunction with Extended activated sludge system downstream (reduced aeration zone to achieve high nitrification overall and a denitrification zone).

6 Table 1 Abattoir Wastewater Quality Parameter Typical Value Range BOD, mg/l 2, ,000 COD, mg/l 5,000 1,300 10,000 TSS, mg/l 3, ,000 TKN, mg/l P, mg/l Total Oil / Grease, mg/l 1, ,500 ph Table 2 Abattoir alternative systems cost for 1.5 ML flow, and with nitrogen reduction Item Uncovered Constructed Covered lagoon, Note All Values in $ 000 lagoon, digester, biogas biogas use, TF activated use, activated and AS system sludge system sludge system (Figure 2) Anaerobic treatment system $ 700 $ 3,500 $ 900 Biogas / cogeneration system $ 0 $ 550 $ 550 Trickling Filter system $ 0 $ 0 $ 900 Activated sludge system (BNR) $ 2,500 $ 2,500 $ 1,950 Sub-Total $ 3,200 $ 6,550 $ 4,300 Contingencies, design, engineering (35 %) $ 1,100 $ 2,300 $ 1,500 Total Capital Cost $ 4,300 $ 8,850 $ 5,800 Annual cost for O/M $ 440 $ 550 $ 390 Potential benefits from Energy $ 0 $ 165 $ 165 Nett Present Cost (5 % discount factor, 20 years) Payback (based on comparison to column #1) $ 9,750 $ 13,600 $ 8, years 7 years

7 Figure 1 Covered Anaerobic Lagoon Figure 2 Schematic diagram of low operating cost system to reduce nitrogen