A bioreactor coupled to a membrane to provide aeration and filtration in ice-cream factory wastewater remediation

A ceramic membrane coupled to a bioreactor has been used in a dual role, combining the alternate functions of system aerator and filter for remediating food industry process waste. The 0.2 μm membrane provided markedly superior aeration to a traditional sparger and kept permeate suspended solids below 50 mg l−1, despite an input of 1510–3800 mg l−1. At 25°C (typical waste-stream temperature), with COD inputs of 13,330 mg l−1 and BOD5 6500 mg l−1, reductions in excess of 95% were obtained. Ammonical nitrogen was reduced from 9–10.2 mg l−1 to <0.3 mg l−1 and total phosphorus from 20–21.2 mg l−1 to <4 mg l−1. With membrane aeration, the indigenous microflora, which built-up to over 109 cfu ml−1, included lactic acid bacteria which helped reduce the impact of periodically high pH (>9) wastes due to CIP chemical release.