Industrial water demand management and cleaner production potential: a case of three industries in Bulawayo, Zimbabwe

Abstract

The combination of water demand management and cleaner production concepts have resulted in both economical and ecological benefits. The biggest challenge for developing countries is how to retrofit the industrial processes, which at times are based on obsolete technology, within financial, institutional and legal constraints. Processes in closed circuits can reduce water intake substantially and minimise resource input and the subsequent waste thereby reducing pollution of finite fresh water resources. Three industries were studied in Bulawayo, Zimbabwe to identify potential opportunities for reducing water intake and material usage and minimising waste. The industries comprised of a wire galvanising company, soft drink manufacturing and sugar refining industry. The results show that the wire galvanising industry could save up to 17% of water by recycling hot quench water through a cooling system. The industry can eliminate by substitution the use of toxic materials, namely lead and ammonium chloride and reduce the use of hydrochloric acid by half through using an induction heating chamber instead of lead during the annealing step. For the soft drink manufacturing industry water intake could be reduced by 5% through recycling filter-backwash water via the water treatment plant. Use of the pig system could save approximately 12 m 3/month of syrup and help reduce trade effluent fees by Z$30/m 3 of “soft drink”. Use of a heat exchanger system in the sugar refining industry can reduce water intake by approximately 57 m 3/100 t “raw sugar” effluent volume by about 28 m 3/100 t “raw sugar”. The water charges would effectively be reduced by 52% and trade effluent fees by Z$3384/100 t “raw sugar” (57%). Proper equipment selection, equipment modification and good house-keeping procedures could further help industries reduce water intake and minimise waste.