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 biological process design and construction of these units. The situation with regards to operation and maintenance is far from satisfactory and also contributes to pond malfunctioning. In this sense, a pond system located at Providencia sugar mill on the southwest region of Colombia, South America was evaluated. The system comprises an anaerobic pond followed by a secondary anoxic pond. The whole system removes 73-82% of the BOD, with 53-70% occurring in the secondary anoxic pond, which is satisfactory despite the predominant conditions of organic overloading. However, TSS removal was low in comparison to BOD removal. The secondary anoxic pond proved to be an efficient treatment unit with the advantage of controlling odour release through photosynthetic bacterial activity. Land area requirements were less than those for green algal facultative ponds.