South Taranaki District Council's Advanced Microbial Digestion Trial

South Taranaki District Council (STDC) in association with Parklink Ltd in March 2012 commenced trialing an innovative solution to remove sludge from the Hawera wastewater treatment ponds using high rate microbial digestion to break down the organic solids (sludge). To date the trial has shown excellent results with up to 22% of sludge volume reduced in 9 months. The council has now committed to continuation of the trial and its use in other council wastewater treatment ponds. While this practice is currently being used successfully in industrial pond systems, to our knowledge this is the first use in municipal wastewater ponds in New Zealand. We believe the experience of STDC could be replicated in other municipal ponds throughout New Zealand, providing a natural, environmentally sustainable and cheaper alternative to mechanical removal and dumping of bio-solids in landfills.

We will describe the challenges of trialing a new innovation in a dynamic environment where sludge is being removed biologically but also being introduced daily by the flows and loads entering the WWTP. It is demanding to calculate rates of removal in a dynamic environment where the sludge is being hydrated and rising vertically while being carried horizontally by winds and currents.