Discharging wastewater into Morrinsville STP - when managed trade waste discharge really does matter
Annual Conference
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Greenlea Premier Meats Limited (GPML) own and operate an export beef processing plant in Morrinsville (Greenlea Morrinsville), and discharge wastewater as trade waste into Morrinsville Sewage Treatment Plant (Morrinsville STP), owned by Matamata Piako District Council (MPDC).
During 2009, MPDC identified that a substantial upgrade of the Morrinsville STP would be required in order to meet the requirements of a new resource consent. MPDC undertook extensive feasibility assessment to determine its preferred option. This option had cost implications in excess of $20M for the community, including two nominated industrial trade waste discharges. MPDC stipulated that the two major industrial dischargers including GPML would contribute proportionally to the upgrade capital costs.
Greenlea Morrinsville undertook independent investigations to determine the most cost effective option for the management of the wastewater generated from its site in order to reduce its direct capital contribution for the Morrinsville STP upgrade as well its exposure to the risk of continued escalation of trade wastes charges that was signalled to the company.
Greenlea Morrinsville determined that the site needed absolute security to its business and the need to progress to develop a treatment plant that allowed the company to unhinge itself from total reliance on MPDC owned STP in future. The best practice option selected by Greenlea Morrinsville was a two-stage biological treatment system (BTS) comprising of anaerobic treatment and biological nitrogen removal (BNR) plant operated as a sequencing batch reactor (SBR). The key consents required were landuse consent to establish a wastewater treatment plant and discharge of emissions to air as a result of combustion of biogas. Strict controls on the site were imposed to maintain effectively “zero tolerance” for adverse effects related to odour, noise and visual aspects for consents that were granted through a notified process.
During 2011, a new BTS was constructed and this nestled between a rail corridor and an existing protected oak grove. The biogas generated from covered anaerobic lagoon was managed with a flare unit. A contingency biofilter was also installed to manage the odour emissions in the event of flare outages.
Following the installation and commissioning of the wastewater treatment plant, the anticipated wastewater load reductions were realised within weeks. In addition to substantial savings against the capital contribution, the BTS is providing Greenlea Morrinsville with a reduction of around 70% of annual trade waste charges.
The decision to treat wastewater on-site at Greenlea Morrinsville has significantly reduced the on-going wastewater management costs for the company while also providing more security for the site. The installation has also significantly helped MPDC in reducing its cost and need for substantial treatment at its plant.