Reuse of wastewater in the food industry


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Test technician preparing test equipment to test a new membrane.
NIG Nutritional samples, showing feed on the left and permeate after treatment on the right.
NIG Nutritional samples, showing feed on the left and permeate after treatment on the right.

Engineers and scientists at an Auckland-based clean tech company developed polyethylene membrane filters that operate at 85 ° C in harsh chemical environments from 1 to 13 pH, allowing food and industrial 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 the potable standard. It is these hydrophilic properties that result in dramatic reductions in industrial wastewater volumes, impurity loads and disposal costs. Hydroxsys technology is available in traditional spiral wound or plate and frame formats that can replace existing wastewater treatment systems or function as a modular, turnkey filtration solution delivered to the site.

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

They operate in harsh chemical environments (pH range 1 to 13) and fluid temperatures up to 85 ° C. The membrane is physically strong, 20-30 microns thick and able to withstand thermal and chemical shock, where previously only expensive ceramic-based membranes worked, and it has a higher packing density allowing for greater membrane surface area per filter module, resulting in a greater flow rate per module. element.

The technology allows for low fouling rates and good performance in environments with high food, oil and fat (FOG) content. It also reduces the volume of water used in cleaning dairy and food processing plants by up to 40%, minimizing wastewater volumes and energy costs due to heat-intensive cleaning and it can be integrated to existing wastewater treatment processes, reducing treatment costs by up to 95%.

Technological tests
Since early 2021, dairy processor NIG Nutritionals has been testing Hydroxsys equipment at its factory in Paerata, south of Auckland. clean, reusable water to reduce fresh water consumption, improve wastewater discharge compliance, and improve overall sustainability.

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

Loud and clear
A pre-DAF balancing tank provided the source raw material, and the test was to validate the performance of the Hydroxsys membrane as a replacement for the DAF system. The test was carried out at a transmembrane pressure of 3 bars with a volume concentration factor of up to 10x. The results, independently verified by Watercare, an Auckland water company with international testing laboratories, showed the waste stream to be clean and clear, with a 99.8% reduction in total waste. suspended solids.

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

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