Abstract
This survey aimed at identifying the current practices and experiences of industrial wastewater treatment in Zimbabwe. In this study, questionnaires were used to assess various companies located in Gweru Kwekwe, Bulawayo and Harare. The information collected identified a gap in the treatment of wastewater from food processing industries in Zimbabwe. Current results indicate that about 86% of the food processing industries surveyed have primary treatment facilities. Few companies have proper secondary treatment facilities. Wastewater was characterised for selected effluents. Electrical conductivity (EC) of the wastewater was also recorded to be lower in most of the samples where dairy effluent showed highest EC by a value of 953 μS/cm. Total dissolved solids (TDS) were observed to be higher in dairy effluent as compared with other effluents. Total suspended solids (TSS) of cereal beverage effluent were higher with a value of 90 mg/L. The highest chemical oxygen demand (COD) values were recorded in potato processing effluent (690 mg/L O2) followed by meat processing effluent (485 mg/L O2). These values however are above the value recommended in S.I.6 of 2007 of 60 mg/L. It was noted that more than 80% of the wastewater comes from production processes and a substantial amount (53%) coming from raw material processing. This study indicates that regular inspections are done to enforce the wastewater legislation. Of all the companies studied, 73% of the companies were disposing their industrial effluent directly into the municipal sewer lines. Without the proper treatment facilities, the disposal of polluted effluent into the public sewer poses health and environmental consequences to the community. It can be concluded from the current data that there is a serious need to establish secondary treatment systems to remove organic load from food processing effluent and reduce pollution. Key words: Wastewater, food processing, pollution, treatment, legislation, disposal.
Highlights
One of the major consumers of environmental resources and producers of environmental damaging agents that cause environemental pollution are the manufacturing industry (Marambanyika and Mutekwa, 2009)
The researchers prepared a questionnaire document which was administered to various food industries of Zimbabwe to ascertain the strategies that they employ in their respective wastewater treatment
Specific wastewater quality information was investigated on the biological oxygen demand, chemical oxygen demand, total solids, total suspended solids, nitrogen content, disposal means and conductivity characteristics of the wastewater
Summary
One of the major consumers of environmental resources and producers of environmental damaging agents that cause environemental pollution are the manufacturing industry (Marambanyika and Mutekwa, 2009). The major types of food production processes include yeast, brewery, fruit, vegetable, oils, dairy, meat and fish (Banu et al, 2008; Cristian, 2010; Kosseva, 2013). These industrial wastes vary widely, with associated differences in the specific wastewater contaminants and in-house operations. In Zimbabwe, industries generally are not fully implementing measures of industrial effluents reduction, which inadvertently encourages environmental pollution (Ikhu-Omoregbe and Masiiwa, 2002) This survey aimed at identifying the current appropriateness of wastewater treatment methods employed from selected food industries in Zimbabwe through characterisation of wastewater that they produce. To encourage management recognition of current and future problems in the pollution area and management action to undertake wastewater treatment
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