Wastewater re-use in the food industry

Engineers and scientists from an Auckland-based clean technology company have developed polyethylene membrane-based filters which perform at 85°C in harsh chemical environments of 1-13 pH, allowing food and industry processors to recycle up to 95% of their wastewater for reuse.

Hydroxsys’ membrane filters have hydrophilic properties that will recycle up to 95% of chemically polluted industrial waste streams to potable standard. It is those hydrophilic properties that drive considerable reductions in industrial wastewater volumes, impurity loadings, and discharge costs. Hydroxsys’ technology comes in traditional spiral wound or plate and frame formats that can replace existing wastewater treatment systems or work as a turnkey, modularised, filtration solution delivered to site. 

How it works Hydroxsys’ patented technology is applied to polyethylene and polypropylene film to produce membrane filters that wet out at zero pressure. It passes water through the membrane while rejecting larger molecules and particulates. In addition, it has a patented surface coating that resists fouling of the membrane, minimising solids accumulating on the membrane surface, helping to maintain a constant flow of water. Hydroxsys’ membrane filters support low-pressure filtration processes, reducing energy input and prolonging membrane life.

They operate in harsh chemical environments (1-13 pH range) and in fluid temperatures up to 85°C. The membrane is physically tough, 20–30-micron thick, and capable of withstanding thermal and chemical shocks, where previously only expensive ceramic-based membranes worked, and it has a higher packing density allowing more membrane surface per filter module giving greater throughput per element.

The technology allows low fouling rates, performing well in high food, oil, and grease (FOG) environments. It also reduces the volume of water used in cleaning dairy and food processing plants by up to 40%, minimising wastewater volumes and energy costs from heat-intensive cleaning and it can be integrated with existing wastewater treatment processes, reducing processing loads by up to 95%. 

Technology trials Dairy processor NIG Nutritionals has been trialling Hydroxsys’ equipment at its facility at Paerata, south of Auckland since the start of 2021. In the trial, the company aimed to reduce the net waste volume from its operations and, in the process, provide a source of clean, re-usable water to reduce freshwater intake, improve wastewater discharge compliance, and enhance overall sustainability.

The trial used two Hydroxsys membranes: PL membrane, which is a symmetric membrane designed for high flow rates in solid separation applications; PA membrane, which is an asymmetric membrane designed for high fat applications. Solid waste like milk fat, protein and oils are removed from the liquid phase, providing a far cleaner waste product. 

Clean and clear A pre-DAF balance tank provided source feedstock, and the trial aimed to validate the performance of the Hydroxsys membrane as a replacement for the DAF system. The trial was run at 3 bar trans-membrane pressure with a volume concentration factor of up to 10x. The results, independently verified by Watercare, a water utility company in Auckland with international standard testing laboratories, showed that the waste stream was clean and clear, with a 99.8% reduction in total suspended solids.

The quality of permeate provided water for washdown and other non-hygiene critical applications. Both chemical oxygen demand and biochemical oxygen demand recorded an average reduction of 65%, key parameters if the water is to be released back into the environment.