Anoxic ponds in the sugar cane industry: a case study from Colombia

Waste stabilisation ponds are a common technology used to treat sugar mill wastewaters in Colombia. Despite this there are problems related to biologi cal process design and construction of these units. The situation with rega rds to operation and maintenance is far from satisfactory and also contribu tes to pond malfunctioning. In this sense, a pond system located at Provide ncia sugar mill on the southwest region of Colombia, South America was eval uated. The system comprises an anaerobic pond followed by a secondary anoxi c pond. The whole system removes 73-82% of the BOD, with 53-70% occurring i n the secondary anoxic pond, which is satisfactory despite the predominant conditions of organic overloading. However, TSS removal was low in comparis on to BOD removal. The secondary anoxic pond proved to be an efficient trea tment unit with the advantage of controlling odour release through photosyn thetic bacterial activity. Land area requirements were less than those for green algal facultative ponds.