Aquaculture can have many positive benefits on food sustainability and conservation of fisheries. However, sustainable aquaculture operations require successful management of wastewater streams to avoid negative impacts on the environment. Recognizing the need to be a good steward of the environment, an aquaculture facility located on the coast of New England is committed to treating its wastewater to protect the receiving water bodies while recovering valuable byproducts.
The operation produces wastewater with chemical oxygen demand concentrations (COD) of approximately 8,700 mg/l and elevated nitrogen concentrations of about 640 mg/l. The customer’s objective is to reuse the treated wastewater and to recover the organic constituents and nitrogen for resale. To achieve this goal, COD level in the treated water has to be reduced below 150 mg/l, and the organic constituents and nitrogen have to be concentrated by a factor of about 4x or above in the reject stream.
These requirements cannot be met using traditional polymeric membranes because the elevated concentration of organics in the feed water would require an expensive pre-treatment system to prevent rapid fouling and loss of throughput. In addition, extracting valuable byproducts from the waste stream is not possible using polymeric membranes because the concentration factor required to make it economically viable to sell the recovered organic constituents and nitrogen cannot be achieved.
Testing was completed on the customer wastewater effluent using a pilot scale treatment system and Cerahelix’s PicoHelix® ceramic nanofiltration membranes.
Test results indicate that the customer will be able to achieve their water reuse objectives and eliminate many environmental permitting challenges associated with wastewater management. The system utilizing Cerahelix membranes achieved over 98% reduction in concentration for every key constituent. The concentration of COD and nitrogen in the retentate were on the order of 4x and 5x, respectively, indicating that recovered byproducts can be sold as a secondary fertilizer product.
A unique benefit to ceramic nanofiltration is the smooth surface of the membrane combined with small (<1 nm) pore size that prevents irreversible fouling. This enhances the efficiency of chemically enhanced cleaning procedures, reducing the time and the amount of chemicals required. The smooth surface also results in higher sustained flux between cleaning cycles, meeting the target flow rate.
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