ABSTRACT
Large volumes of wastewater are generated in Nigeria from industrial activities which often cause water pollution when they are not properly treated before being discharged into receiving water bodies. The conventional wastewater treatment plants are expensive and associated with high running and maintenance cost. These plants are also associated with generation of large volumes of chemical sludge. In view of the global economic recession cheaper options are being considered for treatment of industrial waste water such as brewery wastewater effluents. In this work the suitability of waste stabilization pond (WSP)as a cheaper alternative in the treatment of industrial wastewater was investigated so as to obtain design data, empirical and kinetic parameters for the wastewater treatment in WSP.A pilot WSP was designed and constructed for the treatment of raw brewery wastewater effluent. The Brewery wastewater effluents were collected from Nigerian Breweries PLC, Kudendan light industrial layout, Kaduna.The parameters considered for the design include: temperature, influent flow rate, influent BOD, Net Evaporation which are 28 oC, 0.2 m2/day, 1135.5 mg/L and 0.612 m3, respectively. The pond capacity is 4.7m3 (4700 L) and it was designed to reduce the BOD loading by 90% for a retention period of 21 days at an influent flow rate of 0.2m3/day.The pilot WSP was operated on a continuous steady state flow at an average ambient temperature of 29 OC over the retention period.The parameters that were analyzed on the raw and treated wastewater include: pH, Temperature, Total suspended solids (TSS), Turbidity, Chlorides, Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Electrical conductivity (EC), Total dissolved solids (TDS) and Total Coliform. The mean values of these physicochemical parameters for the raw brewery wastewater for a period of 27 days were 3.76, 29.7 oC, 1048.9 mg/L, 6.09 NTU, 573.5 mg/L, 1128.8 mg/L, 2122.1 mg/L, 1011.8 μS/cm, 826.9 mg/L and 1 E-coli/100 mL respectively. At the retention period of 25 days, the values are 6.7, 27 OC, 199 mg/L, 2.0 NTU, 268 mg/L, 350 mg/L, 660 mg/L,287 μS/cm, 296 mg/L and 9 E-coli/100 ml respectively, after which negligible changes were recorded for the listed parameters at higher detention time. The BOD removal rate constant was 0.088 per day and the BOD-COD correlation was BOD = 0.531COD - 1.960.The BOD removal regression model was BOD = 0.0001t5- 0.0034t4- 0.1419t3+ 6.6096t2-102.09t 1114.5 and the pond performance efficiencies for the reduction/removal of TSS, Turbidity, Chlorides, BOD, COD, Conductivity and TDS are 81%, 67.2%, 53.2%, 69%, 68.9%, 71.6% and 64.2% respectively. The retention time was found to be 25 days as against 21 days calculated and this could be attributed to weather variation which influences the factors that enhance wastewater stabilization such as wind, temperature, and sunlight. The WSP was also found to be cost effective because of its low energy requirement for its operation and low maintenance. The pond performance was also found to be satisfactory and the kinetic parameter obtained can be utilized in the scale up design for industrial scale WSP.