Fouling and wetting of membranes are significant concerns that can impede widespread application of the membrane distillation (MD) process during high-salinity wastewater reclamation. Fouling, caused by the accumulation of undesirable materials on the membrane surface and pores, causes a decrease in permeate flux. Whereas membrane wetting, the direct permeation of the feed solution through the membrane pores, results in reduced contaminant rejection and overall process failure. Lately, the application of MD for water recovery from various types of wastewaters has gained increased attention among researchers. In this review, we discuss fouling and wetting phenomena observed during the MD process, along with the effects of various mitigation strategies. In addition, we examine the interactions between contaminants and different types of MD membranes and the influence of different operating conditions on the occurrence of fouling and wetting. We also report on previously investigated feed pre-treatment options before MD, application of integrated MD processes, the performance of fabricated/modified MD membranes, and strategies for MD membrane maintenance during water reclamation. We also discussed energy consumption and economic aspects of MD for wastewater recovery. Throughout the review, we engage in discussions highlighting research needs for furthering the development of MD: notably the incorporation of MD in the overall wastewater treatment and recovery scheme (including selection of appropriate membrane material, suitable pre-treatment or integrated processes, and membrane maintenance strategies), and the application of MD in long-term pilot-scale studies using real wastewater.

Locally available Indian mustard (Brassica juncea) and Marigold (Tagetes patula) plants can be used in a cost‐effective, environment‐friendly approach for treatment of landfills developed using heavy metal contaminated Buriganga riverbed sediments. In this study heavy metal uptake by Indian mustard and Marigold plants from heavy metal contaminated Buriganga riverbed sediments were assessed. Initial characterization of the Buriganga riverbed sediments showed concentrations of chromium, lead, copper, and zinc in the sediments higher than the toxicity reference values given for these heavy metals in soil for terrestrial plants, and soil invertebrate. The average background concentration of chromium, lead, copper, and zinc in the Buriganga riverbed sediments were found to be 141.5 mg/kg, 34.9 mg/kg, 38.7 mg/kg, and 287.5 mg/kg, respectively. Hence the newly developed area using such landfills poses a great threat to the surrounding flora and fauna. It was observed that both Indian mustard and Marigold plants accumulated these heavy metals in different parts of the plant from the contaminated sediments and were able to maintain a growth rate of more than 90% compared to that in noncontaminated soil. The results indicated rapid phytoextraction of most heavy metals by the Indian mustard during its final growth phase, whereas rapid phytoextraction of most heavy metals was observed in case of Marigold in its initial growth phase. Total chromium, lead, copper, and zinc uptakes (in mg/kg of plant dry weight) by Indian mustard plant in 12 weeks were 102.6, 28.9, 53, and 1861.5, respectively. The uptakes (in mg/kg of plant dry weight) of the same heavy metals by Marigold plant in 12 weeks were found to be 112.3, 104.25, 82.5, and 716.75, respectively. Marigold showed higher uptake efficiency for chromium, lead, and copper, while Indian mustard was found to be more efficient for zinc uptake. Hence both of these plants can be appropriately used as necessary for treating heavy metal contaminated landfills developed using Buriganga riverbed sediments. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 117–124, 2016

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The up-flow anaerobic sludge blanket (UASB) process has emerged as a promising high-rate anaerobic digestion technology for the treatment of low- to high-strength soluble and complex wastewaters. Sewage, a complex wastewater, contains 30–70% particulate chemical oxygen demand (CODP). These particulate organics degrade at a slower rate than the soluble organics found in sewage. Accumulation of non-degraded suspended solids can lead to a reduction of active biomass in the reactor and hence a deterioration in its performance in terms of acid accumulation and poor biogas production. Hydrolysis of the CODP in sewage prior to UASB reactor will ensure an increased organic loading rate and better UASB performance. While single-stage UASB reactors have been studied extensively, the two-phase full-scale treatment approach (i.e., a hydrolysis unit followed by an UASB reactor) has still not yet been commercialized worldwide. The concept of treating sewage containing particulate organics via a two-phase approach involves first hydrolyzing and acidifying the volatile suspended solids without losing carbon (as methane) in the first reactor and then treating the soluble sewage in the UASB reactor. This work reviews the available literature to outline critical findings related to the treatment of sewage with and without hydrolysis before the UASB reactor.

Conductive membranes can offer innovative solutions for membrane fouling control while maintaining enhanced filtration performance. Here, an emerging technique, vacuum filtration assisted layer-by-layer deposition of functionalized multiwalled carbon nanotubes (MWNTs), was used to prepare conductive surfaces on polysulfone (PSf) ultrafiltration membranes. PSf membranes were functionalized with oxygencontaining negatively charged functional groups through oxygen plasma treatment. MWNT-PSf membranes were prepared with 5, 10, 15, and 20 bilayers with amine-and carboxylic-functionalized MWNTs. The prepared membranes were characterized by the thickness, contact angle, and conductivity of the membranes. Scanning electron microscopy images of the membranes confirmed uniform MWNT distribution across the membrane surface. MWNT-PSf membranes exhibited slightly reduced permeability, improved selectivity, and greater conductivity with increasing number of MWNT bilayers and demonstrated almost complete inactivation of Escherichia coli at low applied DC potential (1−3 V). Furthermore, significant (around 99%) degradation of methyl orange during electrofiltration was observed, supporting an expected reduction in organic fouling of the membrane.