Applicability of upflow anaerobic sludge blanket and dynamic membrane-coupled process for the treatment of municipal wastewater.

This study investigated the applicability of dynamic membrane filter (DMF) technology in an upflow anaerobic sludge blanket (UASB) and DMF-coupled process for the treatment of municipal wastewater. The overall treatment performance and effects of hydraulic retention time (HRT), operating flux, and mesh pore size on the UASB + DMF were assessed. The UASB + DMF-coupled process demonstrated removal efficiencies of over 64 and 86% for TCOD and TSS, respectively. The effects of filtration flux and support mesh pore size were investigated and it was found that while there was little impact on the treatment performance, a 67% increase in operating flux resulted in a 25% increase in fouling rate. Similarly, with smaller mesh pore size (Mesh 500 with pore size of 28 µm) the fouling rate increased by fourfold as compared to Mesh 300 (pore size of 46 µm). In consideration of the operation duration and contaminant removal, the DMF with Mesh 300 support layer and operating at 100 L/m2-h was the most efficient configuration for treating the effluent of the UASB operated with a HRT of 6 h. Microbial analyses of the foulant layer revealed changes in relative abundance as compared to the bulk sludge, particularly with the hydrogenotrophic methanogens completely outcompeting the acetoclastic methanogens. Overall, the coupled process improved the system robustness and reduced variability of the treated effluent.

A method to eliminate bromide interference on standard COD test for bromide-rich industrial wastewater.

Chemical oxygen demand (COD) is one of the most important water quality parameters that quantifies the amount of oxygen needed to oxidize oxidizable pollutants (mainly organics) in water samples. However, erroneous COD results were commonly observed for bromide-rich industrial wastewater samples using standard COD test. Bromide in water sample is known to seriously interfere with COD test. However, there is no satisfactory approach to effectively eliminate bromide interference thus far. In this study, two strategies, namely masking and correction, were investigated for their effectiveness to suppress bromide interference. For the masking strategy, silver ion was assessed for its effectiveness to neutralize bromide in water samples through precipitation and complex formation reactions. Silver ion offered only partial masking effect on bromide, while the residue bromide can still cause significant interference on COD determination. For the correction strategy, an equivalent redox reaction reflecting bromide interference mechanism was proposed, and a theoretical correction factor of 0.1 g COD/g Br- was found based on stoichiometry. The effectiveness of the proposed correction factor for bromide interference under different wastewater pollutant matrix was evaluated using different types of wastewater samples (synthetic wastewater, domestic wastewater and bromide-rich industrial wastewater) with varying amounts of bromide (from 0 to 2000 mg L-1) added to the samples. The findings showed that with bromide concentration up to 600 mg L-1, the correction factor of 0.1 g COD/g Br- was applicable to all the tested wastewater samples, suggesting that this correction strategy could be practically used to eliminate bromide interference in standard COD test.

Pretreatment of saline antibiotic wastewater using marine microalga.

A green microalga Chlorella sp. isolated from marine environment was investigated for its potential to pretreat saline antibiotic wastewater containing amoxicillin (AMX). Through Biolog EcoPlate assay, the Chlorella sp. showed its unique carbon source metabolic patterns under autotrophic condition. In addition, the microalga could effectively remove AMX (>99%) under initial AMX concentrations ranging from 10 to 150 mg/L through a treatability test. In the continuous AMX treatment using a lab-scale membrane photobioreactor (MPBR), a stable AMX removal efficiency of 85.6 ±â€¯3.8% was observed. Moreover, with the aid of a subsequent bacterial treatment, the microalgal-bacterial process (the Chlorella sp. pretreatment followed by either intertidal wetland sediment or activated sludge) can achieve simultaneous AMX removal of >99% and total organic carbon (TOC) removal of ∼80%. In general, the microalgal pretreatment showed its great potential in effective removal of antibiotic residues, which could greatly enhance the overall treatment efficiency of saline antibiotic wastewater.