Development and Evaluation of a Hybrid Membrane Bioreactor for Greywater Reclamation
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The development and evaluation of novel treatment and sanitation devices are necessary for the advancement of wastewater management practices. Considering future water demands and the limitation of current supplies, water security will likely become a central issue of the 21st century. To address this concern, a greywater reclamation system for non-potable water applications was developed and evaluated during this research. The reclamation system consisted primarily of a hybrid membrane bioreactor (HMBR), a biological treatment system containing both attached and suspended growth processes and membrane separation. A 10 month pilot study using synthetic and real greywater was conducted at the University of Regina Research and Innovation Centre (RIC). The objectives of this study were to: (1) evaluate treatment performance at various mixed liquor suspended solids (MLSS) concentrations and hydraulic retention times (HRT); (2) evaluate treatment performance at high contaminant loads using high strength synthetic greywater; and (3) evaluate treatment performance following long periods of idle operation. Influent and effluent water quality was evaluated in terms of five-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN), nitrate, nitrite, ammonia, and turbidity. Removal efficiencies were evaluated at MLSS concentrations ranging from approximately 1000 to 4000 mg/L and at HRTs ranging from 8 to 12 hours. An MLSS = 3000 or 4000 mg/L at an HRT of 8 hours yielded optimal results for the treatment of medium strength greywater. Under these conditions, removal efficiencies as high as 99.2%, 97.8%, 99.8%, 99.9%, 97.9%, and 44.8% were achieved for BOD5, COD, turbidity, ammonia, TP, and TN, respectively. When treating high strength synthetic greywater, high removal efficiencies were observed and residual BOD5 and turbidity were below the Canadian Guidelines for Domestic Reclaimed Water for Use in Toilet and Urinal Flushing. The system showed prompt recovery following one, two, three, and four week periods of idle operation and was capable of producing reusable effluent within two days of resumed flow.