Keep Your Effluent Pond – Bio-Shells/Mf – Case Study To Improve Quality
Annual Conference
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The Clutha District Council (CDC) Wastewater Ponds at Kaitangata and Heriot required upgrading to meet new discharge quality requirements. CDC engaged Marshall Projects Ltd (MPL) and Pall Water (PALL) to install Bio-Shells and Microfiltration to improve nitrogen, ammonia, suspended solids, BOD and E-Coli.
The processes implemented for this project are Bio-Shells for the ammonia and BOD reduction installed directly into the existing ponds. The pond effluent was then treated using the Pall Aria Microfiltration system for E-Coli and suspended solids reduction. The Bio-Shells were manufactured by MPL in Invercargill of which 7 are installed in Heriot and 15 in Kaitangata. The Bioshells were developed by the University of Utah, professors Kraig Johnson and Larry Reaveley. Bio-Shells award-winning, patented technology consists of concentrically nested shells that are infused with air from the bottom. They sit on the floor of a lagoon and are completely submerged. As water flows through them, biofilms effectively reduce ammonia-nitrogen, BOD, and TSS in wastewater. The growth of the naturally occurring bio-films is maximised by the way in which oxygen is optimally guided through the domes by their geometry. MPL manufactures and sells patented submergible aerated bio-film reactors under the trade names Bio-Dome & Bio-Shell. For these towns, each Bio-Shell contains an aerated surface designed to remove 1.18kg BOD/Bio-Shell/day and 0.70 kg TSS/Bio- Shell/day, or once BOD and TSS concentrations are below 30 mg/L, 0.11 kg NH4+-N /Bio-Shell/day at 6°C. These are the first of the Bio-Shells installed in New Zealand.
The systems were commissioned in February and March 2018 for Heriot and Kaitangata respectively. The microfiltration systems are operating as expected providing the suspended solids and bacterial removal from the 0.1micron membrane.
The Pall aria AP2 and AP4 units installed at Heriot and Kaitangata use 0.1micron PVDF membranes and are identical to those used in water supply in New Zealand. Direct online integrity testing ensures integrity of the membranes and provides surety that the E-Coli requirements are being achieved.
Whilst pond effluents are often considered high fouling waters for MF, the Pall MF system is not experiencing a high fouling tendency and with time cleaning regimes may be able to be reduced. The paper explores the operational costs in more detail with sustainable operational parameters presented.
The paper will compare historical performance of the ponds verses upgraded performance from proving period laboratory testing.