1.1 Introduction
Onitsha, the commercial nerve of Anambra state, is located in the South-Eastern part of Nigeria. With a population of 840,000 (2006, source: National population commission report). Onitsha is the largest city in the state. The city has many industries, ranging from small to large scale enterprises.
These industries are scattered in almost all the suburbs of the city. They are engaged in the manufacture of a variety of products including alcoholic, beverages, soft drinks, nails, foam mattresses, lumber and plywood. There is also a slaughter house for animals (Sarfo Afriyie 1999). Despite the economic gains derived from these industries routine visits made by the federal Environmental Protection agency (air, water, and land) has shown that most of these industries sink their wastes.
Some of the food processing industries, including food and beverages, breweries, discharge untreated waste water into the public drainage system or River Niger. This disposal practice could cause potential or severe pollution problems to the water bodies since the effluents contains organic compounds that require oxygen for degradation (Sarfo-Afriyie, 1999).
Chemical oxygen demand (COD) measurement is simple and can reliably be carried out in the laboratory. The COD is a measure of the oxygen equivalent of the organic matter of a sample that is susceptible to oxidation by a strong oxidant. The dichromate reflux method has been preferred over procedures using other oxidants because of superior oxidizing ability with a wide variety of samples, and ease of manipulation (Boyle, 1997).
Also if water of high organic matter content or biochemical oxygen demand (BOD) value flows into a river, the bacteria in the river will oxidize the organic matter consuming oxygen from the water faster than it dissolves back in from the air. If this happens, fish will die from lack of oxygen, a consequence known as fish kill. A stream must have a minimum of about 2 mg/l of dissolved oxygen to maintain higher life forms. In addition to this life-sustaining aspect, oxygen is important because the end product of chemical and biochemical reactions in anaerobic systems often produce aesthetically displeasing colours, tastes and odours in water.
Water is a most precious resource. The cleanliness of lakes, rivers and oceans is one of the pressing goals for environmental protection. The balance of nature depends therefore, on the comprehensiveness of the approach to solve the problem of waste water disposal.
1.2 Aim and Objectives of the Study
The aim of this study is to verify the chemical oxygen Demand (COD) level of the precise study areas. This aim will be achieved by seeking to accomplish the following objectives.
- To identify the various types of wastage/effluents being produced in the study area.
- To assess the effluent of the selected industries, through analysis of some selected water quality parameters such as COD.
- To compare the result with national and international standard limit.
- To evaluate various quantitative and qualitative data associated with industrial waste effluents.
1.3 Scope of Study
This is a study of the chemical oxygen demand (COD) levels in selected industrial effluents from Onitsha. The study will focus on the laboratory analysis of the industrial effluent concern, by a systematic analysis of samples for the purpose of this study, effluent from five industries have been designated for sample analysis and these industries include:
- Jacbon Industries Limited,
- Markson Chemical Industries (WIA) Limited,
- Dueman Chemical Industries Limited,
- Chi Beverages Limited and
- Gemok Cream Industries Limited
1.4 Significance of the Study
- One thing is to create awareness on the hazardous effects of these industrial effluents, another thing is to find out ways and proffer solutions to reduce the effects to a minimum.
- This study has become very significant because it will help to find effective solutions to reduce the (COD) chemical oxygen demand level in industries effluents.
- The work will create awareness in the industrial/manufacturing sector by making them know of the dangers which they were hitherto ignorant of (COD) chemical oxygen demand.
- This work will help to inform and encourage the general public and the inhabitants of Onitsha in particular, on environmental effects of industrial effluents.
1.5 Definition of Terms
Effluents:
It is an outflowing of water or gas from a natural body of water, or from human-made structure.
Water Quality:
Refers to the physical, chemical and biological characteristics of water.
Chemical Oxygen Demand (COD):
The COD is a measure of the oxygen equivalent of the organic matter content of a sample that is susceptible to oxidation by a strong oxidant.
Biochemical Oxygen Demand (BOD):
This is a measure of the quantity of oxygen require for the oxidation of biodegrable organic matter present in water by aerobic biochemical action.
Dissolve Oxygen:
It refers to oxygen gas that is dissolved in water. Fish “breathe” oxygen just as land animals do. However, fish are able to absorb oxygen directly from the water into their blood stream using gills, whereas land animals use lungs to absorb oxygen from the atmosphere.
Conductivity:
It is a measure of the ability of water to pass an electric current.
