Waste stabilisation (Oxidation) ponds in New Zealand continue to be a cost effective means of wastewater treatment, but thirty five years’ experience working with pond systems has shown that there are many aspects of these seemingly simple systems that are still not well understood. Improved understanding of pond systems translates to better performance outcomes and greater cost efficiencies for that increasingly limited capital and operating investment.
Recent analysis of 20 pond systems throughout New Zealand presented some interesting findings regarding pond performance outcomes and upgrade strategies. This paper presents some of those findings and follows on from a paper presented by H Archer at the 2015 Water Conference “Can Performance of Waste Stabilisation Ponds be Improved”, and also reviews a paper presented by CW Hickey and JM Quinn to the 1990 IPENZ annual conference “Evaluation of the Performance of Domestic Sewage Oxidation Ponds in NZ”.
The paper looks more critically at pond performance in regard to the 50-year-old New Zealand national design guideline of 84 kg BOD/ha/d, at factors affecting pond performance such as loading, temperature, mixing and sludge accumulation, and at a number of approaches to improve the performance of pond systems with which the author is familiar.