CHEMICAL OXYGEN DEMAND (COD) LEVELS IN SELECTED INDUSTRIAL EFFLUENTS FROM ONITSHA
There is an increasing awareness on the problems of environmental pollution not only in developing countries like Nigeria but worldwide. Among the sources of this problem is effluent discharge from industries, particularly food processing industries. To determine the extent of this problem in Anambra and Enugu States of Nigeria, some industries were purposively selected and their effluent characteristics studied. The industries include Premier Breweries and Life Breweries Plc, all in Onitsha, Anambra State, Anambra Vegetable Oil Production Company (AVOP) Plc, Nnachi, Enugu State, Diamond Breweries Ltd., 9 th Mile Corner, Enugu State and Coca-Cola Bottling Company Plc, Ngwo, Enugu State.
The effluents were collected and analyzed for solids, organics, nitrogen, pH and total coliform using standard procedure. The results showed that total solids (TS) varied 440 to 703 mg/L, total suspended solids (TSS) from 0 to 230 mg/L and total volatile solids (TVS) from 223 to 514 mg/L. The pH of the effluents varied from 6 to 8, the COD from 684 to 3,192 mg/L, the TKN from 5.6 to 33.6 mg/L and the total coliform from 43 to 150 MPN/100 mL of effluent sample. Compared to the effluent limitation guidelines given by Nigerian Federal Environmental Protection Agency, the TSS, and COD for most of the industries are well above the limits while the TKN, pH and coliform count are within the acceptable limit.
Man exerts many effects which directly or indirectly affects his environment. The development of industries and extensive urbanization means increased water consumption and pollution resulting from problems of waste disposal. Unfortunately, in most developing countries like Nigeria, effluent quality standards imposed by legislation (where they exist) are sometimes easily flouted (Okereke, 2007). Industrial effluents are liquid wastes which are produced in the course of industrial activities. Over the years, the improper disposal of industrial effluents has been a major problem and a source of concern to both government and industrialist. In most cases the disposal or discharges of effluents, even when these are technologically and economically achievable for particular standards, do not always comply with pretreatment requirement and with applicable tonic pollutant effluent limitations or prohibitions. The consequence of these anomalies is a high degree of environmental pollution leading to serious health hazards. Among the food processing industries commonly found in the study area are beer breweries, soft drink bottling companies, vegetable oil industries, etc.
Brewery industries produce waste waters like spent cooling water, spent grain liquor, spent hop liquor, liquor from yeast recovery system and wash down waters. In most breweries in Nigeria, these various sources of wastewater are discharged from the industry through a common outlet. Wastes such as dry brewers grain and spent grain are used as animal feedstuff and therefore do not create disposal problems. Brewery wastewaters can be land applied after limited pretreatment (e.g. screening and equalization) if enough land area is available. This depends on which brewery streams are combined for land application, while specific quality characteristics can vary greatly (Otta and Cable, 1987). The vegetable oil processing plants produce oil sludge’s and other wastewaters that are normally land applied after limited pretreatment. Ho
wever, considering the types and interactions of the numerous constituents of these complex waste streams and the necessity to avoid the environmental pollution problems that can result when these wastes are land applied, it is necessary that the characteristics of the effluents from breweries and other food processing industries in a developing country like Nigeria be investigated. The purpose of this study was therefore to investigate effluent quality of some food processing industries in Enugu and Anambra States of Nigeria.
The specific objectives of the study were: (a) To identify some food processing industries in Enugu and Anambra state of Nigeria. (b) To collect and characterize effluent samples from the selected industries with respect to: (i) Total Suspended solids (TSS) (ii) Total solids (TS) (iii) Total Volatile solids (TVS) (iv) Hydrogen-ion concentration (pH) (v) Total Kjeldahl Nitrogen (TKN)