ENGINEERING MANAGEMENT OF ABATTOIR WASTE: A CASE STUDY OF ONYEARUGBULEM MARKET, AKURE

Abstract

The rapid growth in population, urbanization, industries and agriculture practice has led to an increase in the rate of wastewater generation. The main aim of this research is to carry out a comprehensive assessment of the existing wastewater management in Onyearugbulem abattoir and develop the best management practices appropriate for such abattoir. Abattoir wastewater effluent samples were collected from Onyearugbulem Abattoir Market in Ondo State of Nigeria. Wastewater samples from various sections of the abattoir were collected for analysis. Tests were conducted in accordance with Standard Methods for the Examination of Water and Wastewater. The results of the wastewater showed that the effluent was basic with a pH range of 6.9-7.7 and a conductivity of 3000μmhos. The alkalinity was also very high with 750 mg/l as compared with 100 mg/l recommended by National Environmental Standards and Regulation Enforcement Agency (NESREA). The total solid and total dissolved solid were with values ranging from 0.1-5.1 mg/l, and 1.0-6.34 mg/l respectively. The Abattoir wastewater has a hardness of 125 mg/l, ammonia 3.8 mg/l and nitrate 0.33 mg/l. Dissolved Oxygen was 2.5mg/l while COD and BOD were of the values 156mg/l and 24.72mg/l respectively for the initial day. Also, methods were developed for managing the abattoir solid waste. A field and laboratory model of biological pond was planned, designed and constructed for wastewater treatment. The sizes of the ponds constructed for analysis were; 2.657 m х 0.664 m х 0.2 m, 3.985 m х 0.996 m х 0.3 m, and 7.970 m х 1.993 m х 0.6 m respectively with a thickness of 0.5 mm. The ponds represented aerobic and anaerobic treatments with control experiments. In aerobic treatment pond, the odour was eminent for the 30th day of treatment, The temperature ranged between 24-310C, Also, the conductivity after treatment at 30th day for the biggest aerobic pond was 1000 ɥohms, which corresponds to the NESREA and FEPA requirements for abattoir wastewater analysis, and for the 2nd and 3rd pond were 1100 ɥohms and 900 ɥohms respectively. The sulphate was 99 mg/l, the alkalinity was 100 mg/l and the BOD was 2.0 mg/l which was less than 25mg/l as recommended by National Environmental Standards and Regulation Enforcement Agency (NESREA). In the anaerobic treatment pond, the BOD ranged between 10-20.37 mg/l which was less than 25mg/l. At day 20, the nitrate was 2.0 mg/l which were supposed to be 10 mg/l for a treated wastewater. In the aerobic control experiment, nitrate was not detected from the fifth day of treatment until the 30th day with a value of 0.01 mg/l while NH3 was minimal with values which ranged between 0.1 mg/l - 2.41 mg/l, though the pH was within the range required which was 7.2-7.9. In the anaerobic control experiment, the wastewater was treated to an alkalinity of 100mg/l required, the BOD was 10 mg/l. The odour and the colour are unobjectionable. The microbial load of the wastewater was also detected with values ranging from 35-309 Cfuх106, 60-300 Cfuх106, 65-305 Cfuх106, 56-340 Cfuх106, 25-350 Cfuх106 and 13-104 Cfuх106 , on the 5, 10, 15, 20, 25 and 30 days under various treatment. The results of the analysis made from samples collected from the pond after specified detention days showed that the physic-chemical properties reduced greatly with some of the parameters falling within the stated limits by World Health Organization and NESREA. About 90% and 85% of BOD and COD were removed from the effluent respectively. The pH of the treated samples ranged from 6.8 to 7.5. This shows the basicity of the treated abattoir wastewater. Conductivity and nitrate were reduced by 75% and 70% respectively. Removal of total solid was 90%. Alkalinity, chloride, hardness and also reduced by 95%, 89% and 39% respectively. The values of Chloride, nitrate, conductivity, alkalinity, acidity, COD and BOD after 30 days in aerobic pond fell within the standard limit provided by FEPA and NESREA. However, total solid, hardness, sulphate and dissolved oxygen failed to meet the standard. In the design of the biological pond, maximum consumption of water used was required by knowing the number of cows slaughtered, considering the length, breadth, and height. The capacity of the pond was designed to be at least four times greater than the flow of effluent. Thus, the size of the pond was 39.8498 m х 9.9624 m х 3 m with a free board of 0.5 m. The study was concluded with appropriate recommendations to address the problem and as well suggested the exclusion of abattoir facility from residential neighbourhood.