Studies on the characteristics and treatment of selected food industrial effluents in Nairobi

Abstract

All industrial processes, regardless of product or size generate wastewater by the nature of their respective operations. The circumstances of industries are so varied that there is no general solution to the problem of industrial wastewater treatment and disposal. The volume and characteristics of waste produced vary from industry to industry even within the same industry from time to time. Thus adequate data and knowledge of the characteristics and nature of an industrial waste is a pre-requisite for finding an appropriate method for its treatment. This study investigates the characteristics and treatment of two types of industrial effluents, in Nairobi. The wastewaters were obtained from Kenya Cooperative Creameries (K.C.C) at Dandora and Tusker Brewery at Ruaraka. The K.C.C handles about 300,000 litres of milk per day while the Tusker brewery produce-s -about, 2.25 million litres of beer per;day. The wastes were analysed

for BOD, COD, alkalinity, permanganate value, pH, 5 suspended solids, dissolved solids, chloride,

ammoniacal nitrogen, albuminoid ammonia, nitrite

nitrogen, and nitrate nitrogen, for a period of six months. The results show that the characteristics and nature of the dairy and brewery wastes are such that they could be pre-treated adequately using simple biological treatment methods. Two anaerobic pond models, each of size 0.2 m wide, 0.4 m long and 0.6 m deep (capacity of 48 litres) were then used, for a period of three months, for treating the dairy and brewery wastes. The flow rates to the ponds (which were originally intended to be fed and operated at 5 day detention time) were observed to fluctuate widely during operation. Influent to and effluent from the ponds was analysed for the same parameters as for wastewater characteristics determination. Treatment data indicated an average BOD removal of about 85.8% for the pond receiving the dairy waste and a BOD reduction of only about 46.4% for the pond treating the brewery waste. The average percentage reductions in COD and 55 were 80.6% and 88.0% respectively for the dairy waste, and 52.0% and 85.1% respectively for the ~rewery waste.