Enhancing the performance of a wastewater treatment plant processing wheat starch factory tailings

Abstract

The performance of a waste water treatment plant (WWTP) at a wheat starch factory (average flour throughput of 59 t/day) is reported in this paper. Most factory-generated wastestreams were processed through the onsite WWTP prior to being discharged to a municipal wastewater treatment facility for further treatment. One stream was trucked off-site as 'liquid fertiliser'. Over the two-year monitoring period, the onsite WWTP discharged an average of 430 kL of wastewater per day (range 323-3,264, standard deviation 198) with an average suspended solids (SS) concentration of 2,500 mg/L (range 610-11,700, standard deviation 1,568) and an average BOD5 of 1,950 mg/L (range 140-13,000, standard deviation 1,855). Impacts to the WWTP as a result of water usage and wastewater generation practices within the manufacturing plant were investigated. The operation, effectiveness and maintenance of the system were assessed in terms of how water usage and practices within the starch recovery process affected effluent treatment performance. By-products of the treatment process included beneficial and non-beneficial outputs. For example, methane generated in the anaerobic digester was utilised in the boilers and offset the purchase of natural gas costs while excess anaerobic sludge posed a disposal problem, as there was no local market for this material. Performance inhibitors were identified during the study, as well as the consequences of failure of the anaerobic digester. Recommendations, based on theoretical background and practical experience are provided for enhancing this kind of treatment system and for reducing overall water usage in the starch factory.