Characterization of Wastewater from an Abattoir in Rwanda and the Impact on Downstream Water Quality

Abstract

This study analyzed processes and products at Nyabugogo Abattoir in Kigali, Rwanda, and investigated how they can be optimized for environmental safety. The average capacity of the abattoir is 566 cattle and 1,512 goats and sheep slaughtered per week. The study assessed the quantity and quality of different raw materials, by-products and wastewater streams and the potential impacts of applying cleaner production principles in abattoir processes. The samples were collected fortnightly, and analyzed using Standard Methods. The analysis emphasized on nutrients, biologically active constituents, and receiving water impacts. The data were processed for trends and variance using SPSS computer package. The wastewater parameters analyzed are temperature, salinity, conductivity, turbidity, dissolved oxygen pH, TSS, TDS, BOD5, COD, fat oils and grease, NO3-N, TKN, total phosphorus, chloride, calcium and total coliforms. The findings showed that the abattoir wastewater streams’ total chemical oxygen demand (TCOD) ranged from (7,533±723) for evisceration to (23,778±1,673) mgl-1 from slaughtering step and the discharge into Mpazi River increased its TCOD from (213±29) to (852±94) mgl-1. The TSS varied between 2,452±51 from the slaughter process and 5,252±174 mgl-1 for the effluent from the goat and sheep slaughter section. Results from the bacteriological analysis showed that the average abattoir wastewater discharge count was (560±81)*105 cfu/100ml of total coliforms which increased from (2.8±0.58)*105 to (8.2±0.86)*105 cfu/100 ml. It was concluded that the current effluent quality is not suitable for discharge into watercourses. It was recommended that further treatment of the effluent is required coupled with the application of cleaner production principles.