Can Performance Of Waste Stabilisation Ponds Be Improved?

There are over 200 waste stabilisation pond treatment plants in New Zealand which represent a substantial asset value. Common criticisms of ponds include;

• Ponds have caused nuisance odours in some locations
• Faecal Indicator Bacteria (FIB) removal by ponds relies on natural processes and is too variable
• Algae in pond effluent cause colour effects in receiving waters
• Nutrients cannot be removed in ponds
• Sludge removal from ponds is difficult and expensive

These criticisms can be countered by describing the successful upgrading works that have been implemented at a number of pond sites in NZ, along with the subsequent performance improvements. This paper focuses on ponds which the author has first-hand experience of (at 50 WWTP sites with pond systems), but will also comment on other pond sites where problems have arisen.