5. TREATMENT OF POULTRY SLAUGHTERHOUSE WASTEWATER USING A
5.1 Introduction
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5. TREATMENT OF POULTRY SLAUGHTERHOUSE WASTEWATER
Table 5-1: Water consumption in a typical South African poultry slaughterhouse (Molapo, 2009)
Area Operations
Water consumed (% )
Average water consumed (% )
Processing
Lairages
Slaughter and carcass dressing Offal handling
5 – 12 12 – 33 11 – 60
10 20 25
Utilities
Hot water Cooling and refrigeration
Steam raising
14 – 36 5 – 11
2 – 9
25 8 5 Services Ablutions, laundry and general washing 1 – 12 7
The composition of this wastewater may differ from one slaughterhouse to another depending on the type of bird, the water consumption per processed bird, as well as the type of process used (Debik & Coskun, 2009; Del Nery et al., 2007). These wastewaters are typically characterized by high concentrations of organic compounds such as BOD5 and tCOD, including high levels of nitrogen, phosphorous, pathogenic microorganisms, suspended solids, and FOG as a result of blood, faeces, carbohydrates, feathers and proteins (Oh et al., 2014; Yornadov, 2010), as highlighted in Table 5.2. The high content of organic matter can be attributed to the residual blood in the wastewater (Dlangamandla, 2016; Debik & Coskun, 2009). The chemical constituents present in the wastewater mostly originate from the cleaning and sanitizing stages, stages which while accounting for a large proportion of the water consumed, are crucial for ensuring that the process is hygienically safe, and the poultry products are fit for human consumption (Mohammed, 2014; Department of Agriculture and Rural Development, 2009). The choice of treatment method and design of equipment used in the wastewater treatment process are influenced by the quality and quantity of wastewater generated (Molapo, 2009). Table 5.2 summarizes the characteristics of poultry slaughterhouse wastewater, including treatment methods used.
56 Table 5.2: Poultry slaughterhouse wastewater characteristics and treatment methods used
Treatment process Parameters Reference
tCOD (mg/L)
BOD5
(mg/L) pH -
TSS (mg/L)
FOG (mg/L)
Static Granular reactor 3137-7864 1543-5732 5.6-6.9 840-2355 - Oh, 2012
Sequencing Batch Reactor and Chemical DAF
2060-4380 1559-26983 6.3-7.0 480-1230 131-261 De Nardi et al., 2011
Ultra-Filtration 3610-4180 1900-2200 - 2280-2446 289-389 Yordanov, 2010
Static Granular reactor
4200-9100 - 5.6-8.1 1850-3750 - Debik & Coskun, 2009
Chemical DAF and Up- flow Anaerobic Sludge Bed Reactor (UASB)
2360-4690 1190-2624 6.5-7.0 640-1213 249-702 Del Nery et al., 2007
UASB
2000-6200 1300-2300 6.3-6.6 850-6300 40-600 Caixeta et al., 2002
Treatment methods – such as physical, chemical, and biological processes (Kiepper, 2001) – have been utilized for the treatment of poultry slaughterhouse wastewater.
Each process type has both unique treatment advantages as well as operational limitations. Table 5.3 provides a brief summary of these treatments methods.
Table 5.3: Poultry slaughterhouse wastewater treatment technologies (Mol apo, 2009; Mittal, 2005; Kiepper, 2001; Masse, 2000; Johns, 1995)
Treatment
Type Physical Treatment
Chemical Treatment
Biological Treatment
Application
Treatment Method
Removal of suspended solids, fats oil and grease
Screening, fat traps, catch basins, settling
Removal of fats, suspended solids, nutrients
Dissolved air flotation (DAF) chemical flocculation, electrocoagulation
Removal of organic matter (COD and BOD), pathogens
Activated sludge systems, anaerobic and aerobic systems
Biological treatment methods primarily involve the removal of organic compounds and deactivation of pathogens from wastewater using microorganisms (Molapo, 2009). There are two types of biological treatment processes, namely aerobic and anaerobic treatment systems. Both processes require sufficient contact time between the wastewater and the microorganisms for effective treatment (Kiepper, 2001).
Anaerobic treatment reduces organic compounds to methane and carbon dioxide using microorganisms in the absence of molecular oxygen (Mittal, 2005). Poultry slaughterhouse wastewater is well-suited to anaerobic treatment because it contains high concentration of organic compounds (Debik & Coskun, 2009). Treatment processes included in this category are lagoons, anaerobic contact (AC) reactors, up- flow anaerobic sludge blanket reactors (UASB), expanded granular sludge bed reactors (EGSB), static granular bed reactors (SGBR) and anaerobic filter (AF) processes.
In the food processing industry, anaerobic treatment technology is one of the most widely used treatment methods due to its advantages of treating high strength
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anaerobic digestion systems have been used in treating poultry slaughterhouse wastewater due to their ability to handle high concentrations of particulate matter and FOG. The up-flow anaerobic sludge bed (UASB) reactor is also widely used to treat poultry slaughterhouse wastewater. Debik et al. (2009), using the static granular bed (SGBR) reactor to treat poultry slaughterhouse wastewater, obtained an average tCOD removal of 95%. Similarly, Del Nery et al. (2005) obtained a 65% total and 85%
soluble tCOD reduction at an average organic loading rate (OLR) of 1.64 kg COD/m3.day using a full scale UASB reactor. For high treatment efficiency, these treatment systems can be combined with other systems to improve efficiency. For example, De Nardi et al. (2008) investigated the use of a Dissolved Air Floatation (DAF) as a pre-treatment prior to the UASB reactor in order to lower the influent FOG and suspended solids load, a strategy which improved the UASB functionality.
Yodanov (2010) reported tCOD removal greater than 94% for treatment of poultry slaughterhouse using ultra-filtration membrane systems.
In this study, the feasibility of using a two-stage process in which a mesophilic Static Granular Bed Reactor (SGBR) coupled with to a UF membrane system was investigated. The use of this two-stage system has not yet been applied at an industrial scale in SA, particularly for the treatment of poultry slaughterhouse wastewater. The purpose of this study, then, was to evaluate the treatment efficiency of a lab-scale SGBR anaerobic digester coupled with a UF membrane system for effective tCOD reduction for poultry slaughterhouse wastewater, in order for the treated wastewater to comply with the City of Cape Town (CCT) by-law discharge standards for assessing the quality of industrial wastewater.