Mineralizing urban net-zero water treatment: Field experience for energy-positive water management

• Published in: Water research (Oxford) Vol. 106; pp. 352 - 363
• Main Authors: Wu, Tingting, Englehardt, James D.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.12.2016
• Subjects: Advanced oxidation; Biological Oxygen Demand Analysis; Bioreactors; Byproducts; Direct potable reuse; Drinking water; Energy; Freshwater; Hormones; Hydrogen Peroxide; Mineral Waters; Mineralization; Net zero water treatment; Oxidation; Rain water; Waste Disposal, Fluid; Wastewater treatment; Water Purification; ASW, USA, Florida; Direct potable reuse; Net zero water treatment; Advanced oxidation; Energy; Mineralization
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2016.10.015

An urban net-zero water treatment system, designed for energy-positive water management, 100% recycle of comingled black/grey water to drinking water standards, and mineralization of hormones and other organics, without production of concentrate, was constructed and operated for two years, serving an occupied four-bedroom, four-bath university residence hall apartment. The system comprised septic tank, denitrifying membrane bioreactor (MBR), iron-mediated aeration (IMA) reactor, vacuum ultrafilter, and peroxone or UV/H2O2 advanced oxidation, with 14% rainwater make-up and concomitant discharge of 14% of treated water (ultimately for reuse in irrigation). Chemical oxygen demand was reduced to 12.9 ± 3.7 mg/L by MBR and further decreased to below the detection limit (<0.7 mg/L) by IMA and advanced oxidation treatment. The process produced a mineral water meeting 115 of 115 Florida drinking water standards that, after 10 months of recycle operation with ∼14% rainwater make-up, had a total dissolved solids of ∼500 mg/L, pH 7.8 ± 0.4, turbidity 0.12 ± 0.06 NTU, and NO3-N concentration 3.0 ± 1.0 mg/L. None of 97 hormones, personal care products, and pharmaceuticals analyzed were detected in the product water. For a typical single-home system with full occupancy, sludge pumping is projected on a 12–24 month cycle. Operational aspects, including disinfection requirements, pH evolution through the process, mineral control, advanced oxidation by-products, and applicability of point-of-use filters, are discussed. A distributed, peroxone-based NZW management system is projected to save more energy than is consumed in treatment, due largely to retention of wastewater thermal energy. Recommendations regarding design and operation are offered. [Display omitted] •A first field demonstration of advanced oxidation-based net-zero water treatment.•Product water met 115 of 115 drinking water standards with COD below detection.•97 of 97 selected emerging contaminants not detected.•System projected energy-positive due to hot water energy retention.•Design and operating recommendations for 85% recycle rate offered.