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Improving wastewater treatment process and water desalination are two important solutions for increasing the available supply of fresh water. Microbial desalination cells (MDCs) with common electrolytes display relatively low organic matter removal and high cost. In this study, sewage sludge was used as the substrate in the Microbial desalination cell (MDC) under three different initial salt concentrations (5, 20 and 35 g.L) and the maximum salt removal rates of 50.6%, 64% and 69.6% were obtained under batch condition, respectively. The MDC also produced the maximum power density of 47.1 W m and the averaged chemical oxygen demand (COD) removal of 58.2 ± 0.89% when the initial COD was 6610 ± 83 mg L. Employing treated sludge as catholyte enhanced COD removal and power density to 87.3% and 54.4 W m, respectively, with counterbalancing pH variation in treated effluent. These promising results showed, for the first time, that the excess sewage sludge obtained from biological wastewater treatment plants could be successfully used as anolyte and catholyte in MDC, achieving organic matter biodegradation along with salt removal and energy production. In addition, using treated sludge as catholyte will improve the performance of MDC and introduce a more effective method for both sludge treatment and desalination.

Biological treatment of a high strength chesses whey wastewater was investigated in a series of aerobic-anaerobic experiments. Aerobic treatment of the wastewater was conducted in a three-stage rotating biological contactor (NRBC), while the anaerobic process was performed in an up-flow anaerobic sludge fixed film (UASFF) bioreactor. Various concentrations of wastewater with influent COD of 40,000 to 70,000 mg/L were introduced in to NRBC system. Treatability of the samples at various HRTs of 8, 12 and 16 h was evaluated in the NRBC reactor. The effluent streams of the NRBC system were introduced into UASFF bioreactor. Anaerobic treatment of the pretreated samples was investigated in an UASFF with the same HRTs of 8, 12 and 16 h. The obtained results revealed that more than 53, 69 and 78% of the influent COD (50,000 mg/L) were removed in NRBC reactor at HRTs of 8, 12 and 16 h, respectively. Maximum COD removal efficiencies of 96, 96.8, 97.4 and 96.4% were achieved in the combined systems at total HRT of 32 h for influent COD of 40,000, 50,000, 60,000 and 70,000 mg/L, respectively.

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The microbial desalination cell (MDC) is known as a newly developed technology for water and wastewater treatment. In this study, desalination rate, organic matter removal and energy production in the reactors with and without desalination function were compared. Herein, a new design of plain graphite called roughened surface graphite (RSG) was used as the anode electrode in both microbial fuel cell (MFC) and MDC reactors for the first time. Among the three type of anode electrodes investigated in this study, RSG electrode produced the highest power density and salt removal rate of 10.81 W/m and 77.6%, respectively. Such a power density was 2.33 times higher than the MFC reactor due to the junction potential effect. In addition, adding the desalination function to the MFC reactor enhanced columbic efficiency from 21.8 to 31.4%. These results provided a proof-of-concept that the use of MDC instead of MFC would improve wastewater treatment efficiency and power generation, with an added benefit of water desalination. Furthermore, RSG can successfully be employed in an MDC or MFC, enhancing the bio-electricity generation and salt removal.

Cheese whey effluent contains biodegradable organic compounds in the range of 40 to 80 g·L–1. In this study, a three–stage rotating biological contactor was fabricated as a bench scale experimental unit to remove organic matters from cheese whey. First, the treatability of cheese whey effluent in the three–stage rotating biological contactor (RBC) was evaluated. Then the effect of extended specific surface area (SSA) and recirculation rate on COD removal was investigated. The obtained results showed that the organic removal rate increased with an increase in loading rate, till other limiting parameters affect the process. Prior to application of the designated modifications to the system, maximum COD removal efficiency at hrts of 24 and 36 h with OLR of 50 gcod·L–1·d–1 was 90 and 92.4%, respectively. The removal efficiency was improved as a result of increasing the SSA and recirculation rate. Also, recirculation rate may assist to increase the DO level of the wastewater, especially at high olrs. To sum up, obtained results showed that whey effluent has been efficiently treated in a continuous operation of bench scale RBC.

Various technological methods are available for industrial wastewater treatment; from conventional to advanced treatment processes. Hence, it is a difficult task to select the most appropriate technology to treat industrial wastewater at a particular location. Many factors are involved in the decision‐making process, including capital, operation, and maintenance costs, as well as land requirement. The present work reports the results of the application of multiple‐attribute decision‐making (MADM) tool to industrial wastewater treatment plants operated under a hybrid aerobic/anaerobic biological process. At the first step, nine industrial wastewater treatment plants were evaluated and ranked by eight criteria using the Vikor method. Among the selected criteria, land requirements, energy consumption, and excess sludge production had the most pronounced effect on the decision‐making process. The results also indicated that the integration of upflow anaerobic fixed bed with intergraded fixed‐film activated sludge process could be used as the most appropriate treatment technology with a Vikor index of one. The result can provide wastewater treatment professionals and water agencies with an effective tool to choose the most appropriate hybrid process for industrial wastewater treatment plants. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019

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