Leading-edge solution for waste water
When Open Country Dairy started review options for a new wastewater treatment plant at its Waharoa site, the decision was made to start with a clean sheet of paper.
Chief executive Steve Koekemoer says challenging the status quo for treatment and disposal options was paramount to the site’s success in order to create a sustainable model for the industry, the community and the environment.
A number of key goals were developed in reviewing the options:A significant reduction in the volume of material requiring off-site disposalA significant reduction in energy consumption for the processA leading-edge wastewater treatment facility that would set the standard for future industrial developments.
To produce a treated wastewater quality which will have no discernible effect on the receiving environment even with the limited background fl ow in the receiving water.A strong focus on value recovery through biological processes which convert the waste into a usable commodity.
The Waharoa site had already undergone a number of waste reduction initiatives such as the re-use of condensate from the milk evaporators for cleaning water and recovery and reuse of cleaning chemicals. However off-site disposal was becoming challenging, both from a logistical perspective and as a cost of operation.
The proposal for the new process would need to be able to significantly reduce the scale of the off-site disposal operation.No solutions that could deal with all these aspects were available, but with the knowledge and expertise of wastewater experts at Hamilton company BPO Ltd, new technology was developed.
This involved wastewater from the factories being received in small pumping stations. A continuous monitoring loop measures a number of parameters and then apportions the wastewater to the high strength, low strength or storage systems.
“High-strength waste goes into an anaerobic process or waste to energy plant. Anaerobic digestion, a biochemical process which converts organic matter to energy in the form of biogas is not a new technology, however it is not a technology typically used in the New Zealand industry.”
Segregating off the high-strength portion maximised the process efficiency and space available for the plant. The gas generated by the process is utilised to heat the wastewater to the optimal temperature for bio-digestion. The excess biogas, if converted to electricity, has the potential to generate the energy required for the operation of the treatment plant, hence creating an energy neutral process.
The effluent from the high strength system and the low strength wastewater are combined and go to a multi-stage aerobic process. The aerobic treatment process coupled with membrane filtration facilitates the removal of residual organic matter and nutrients in a series of biochemical reactions.
“The new treatment plant will generate substantially less excess biomass compared to the current and other conventional dairy treatment plants since the majority of the dairy processing residues will be converted to biogas rather than new biomass.”
The small amount of biomass generated through the process is decanted to remove excess moisture. This product is a relatively inert bacterial mass, rich in nutrients ready to be re-used as a fertiliser and soil conditioner, returning organic carbon, nitrogen, phosphorous and other nutrients back into the soil.
Odour management has been a major focus for the design team. Foul air from the various parts of the process are captured and pumped through a bark biofilter to naturally strip the malodorous compounds.
The process has been designed with a high degree of robustness and adequate operating redundancy to ensure uninterrupted operation throughout the dairy season. The new treatment plant gives Open Country Dairy the peace of m ind and space to focus on their core business objectives of sustainable dairy processing.
The first phase of the treatment plant was commissioned successfully in December 2019; the second and final phase will start commissioning late February. As a show of confidence in the technology, Steve was comfortable to drink the water directly exiting the treatment plant.
“We have been 100 percent committed to this project and are confident that we are installing the best solution to future-proof the business. “Our goal was clear, we wanted the water to be treated to a level that would allow the treated water to enter any waterway.”
“One area we have a great track record in at Open Country is pushing the boundaries and stretching ourselves. “It is very rewarding for the teams involved to see how this project is coming to life and deliver on what it promised.”
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