Evaluation of Critical BOD Loadings from Mauritian Sugar Factories to Streams and Standards Setting

The setting of environmental standards should be based on sound, logical, scientific grounds. One consequence of setting high standards in the developed world is that they are frequently copied by developing nations. The sugar industry in Mauritius has traditionally been a major consumer of water and an important point source of organic pollution in surface water bodies. Strong public pressure and the need to protect water resources in the wake of further industrialization during the past decade have forced the Mauritian authorities to adopt discharge standards to all water sinks. These standards are viewed by the Sugar Industry as being based upon non-scientific and non-economic rationales. This view has led to a loss of credibility of standard setting and to an atmosphere of complacency, all of which impede future efforts to enforce environmental regulations. Developing countries like Mauritius need to maximize their available resources by utilizing the best scientific/economic rationale possible. There was a need to carry out further research, island wide, to clarify and quantify more exactly the environmental impact of sugar-industry wastewaters before the imposition of rigid standards. Models provide the ability to develop, in the short term, a credible and defensible water quality management programme. To optimize the modelling exercise, the level of complexity and input parameter uncertainty must be taken into consideration. Focussing on one issue, to the exclusion of the other, will not, in general, give an optimal solution. The loading concept, based on simple water quality models, produces useful values for managing the point-sources of pollutants in bodies of water in developing countries like Mauritius, which are characterized by a paucity of baseline data. This paper discusses the results of the application of a simple water quality model which yields the critical biochemical oxygen demand (BOD) load which can be discharged into Mauritian rivers so as to maintain the dissolved oxygen (DO) above a desirable level. The proposed Mauritian standards are reviewed accordingly.