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Hazardous airborne pollutants are frequently emitted to the atmosphere in the form of a gaseous mixture. Air biofilters as the primary biotechnological choice for waste gas treatment (low inlet concentration and high gas flow rate) should run properly when the feed contains multiple pollutants. Simultaneous removal of pollutants in biofilters has been extensively studied over the last 10 years. In this review, the results and findings of the mentioned studies including different groups of pollutants, such as methane (CH

Sewage from residents and industries is collected and transported to wastewater treatment plants (WWTPs) with sewer networks. The operation of WWTPs results in emissions of greenhouse gases, such as methane (CH4), mostly due to sludge anaerobic digestion. Amounts of emissions depend on the source of influent, i.e. municipal and industrial wastewater as well as sewer systems (gravity and rising). Wastewater is the fifth-largest source of anthropogenic CH4 emissions in the world and represents 7-9% of total global CH4 emissions into the atmosphere. Global wastewater CH4 emission grew by approximately 20% from 2005 to 2020 and is expected to grow by 8% between 2020 and 2030, which makes wastewater an important CH4 emitter worldwide. This review initially considers the emission of CH4 from WWTPs and sewer networks. In the second part, biotechniques available for biodegradation of low CH4 concentrations (

Arsenic presence in the water has become one of the most concerning environmental problems. Electrocoagulation is a technology that offers several advantages over conventional treatments such as chemical coagulation. In the present work, an electrocoagulation system was optimized for arsenic removal at initial concentrations of 100 µg/L using response surface methodology. The effects of studied parameters were determined by a 2

The presence of recalcitrant dissolved organic matter (DOM) could have a significant effect on the adsorption mechanism and capacity of the sludge for many trace organic carbons (TrOCs). In this study, adsorption of three TrOCs on the sludge and HA was investigated. The results revealed that neutral hydrophilic compounds had an insignificant interaction with both sludge and HA. Positively charged compounds, such as fluoranthene, had more affinity toward HA than sludge with solid/liquid partitioning of 57 and 3.2 L/g, respectively. The adsorption intensity (Kf) of di-2-ethyl hexyl phthalate was 0.5 and 1.13 for the HA and the sludge, respectively. By introducing the sludge to the solution of HA and TrOCs that already reached equilibrium, the sludge adsorption capacity in the presence of HA was investigated. The finding showed that at the lower concentration, adsorption of HA on the sludge was considered as the main removal pathway for the adsorbed emerging contaminants, as 70 mg of HA was adsorbed ...

Biodiesel production across the globe has resulted in a proportional increase of crude glycerol (CG) as waste by-product. Utilization of CG will increase the economic viability of the biodiesel industry. This study compared the energy balance for CG utilization during dark fermentation for hydrogen production with glycerol purification for glycerol. The energy balance for each of the materials used during inoculum, media preparation steps and electricity consumed across both the methods was calculated. The total energy input for glycerol purification (872.39 MJ) was 2.5-fold higher in comparison to maximum total energy input of vegetable feedstock derived CG (344.25 MJ). The market value of pure glycerol is decreasing in comparison to increasing market value of hydrogen as fuel. For efficient utilization of CG, bioconversion to hydrogen production by dark fermentation can be considered an energy efficient and sustainable fuel generation option. The net energy (MJ) for different feedstocks (vegetable source 158.90, multi-feedstock 113.23 and animal waste 83.14) during hydrogen production varied with glycerol content. Performing dark fermentation at ambient conditions and utilization of electricity generated from biogas capture will surely reduce the total energy input. By doing so, the net energy for different feedstocks will have a positive value.

Valorization of crude glycerol (CG), a waste of biodiesel production process, was investigated for increased hydrogen production by co-culture system using Enterobacter aerogenes NRRL B-407 and Clostridium butyricum NRRL B-41122. The ability of E. aerogenes was evaluated as a replacement of expensive reducing agent to maintain anaerobic conditions for the growth of C. butyricum. The co-culture resulted in increased hydrogen production, reaching a maximum of 19.46 ± 0.95 mmol-H2/L-medium in comparison to monoculture of E. aerogenes (15.64 ± 0.47) and C. butyricum (17.44 ± 0.38) in the presence of reducing agent. The effect of inoculum ratio was investigated and hydrogen yield was 0.95 mmol-H2/mol-glycerol at 1:11 inoculum ratio with more than 85% of substrate utilization was comparable to other mixed and co-culture studies. In addition to hydrogen, value added by-products such as 1,3-propandiol, acetic acid, butyric acid and ethanol have also been produced. Co-culture indicated the possibility of v...

In coming years, the generation of organic wastes will exceed 250 billion tonnes worldwide. The organic wastes offer plentiful source of readily available and inexpensive substrates for fermentative hydrogen production. A sustainable approach for hydrogen production from various methods, such as photo-, dark fermentation and sequential two-stage has significant advantages to complement traditional process. During hydrogen fermentation, defined, well-characterized and composite microorganisms are studied. Substantial research efforts have been carried out to increase hydrogen production by using co-culture system, which offers advantage of increased H2 yield and production rate in comparison with mono-culture. The concept of co-culture system is a simple step of mixing different microbial strains for improving the individual properties that other strain lacks. Co-culture system is cost-effective, which potentially eliminates pretreatment step and avoids the use of expensive reducing agent. By eliminating t...

Biofiltration process using peat as media has been shown to be efficient for the treatment of agroindustrial, chemical and municipal effluents. However, determining the hydraulic retention time of this process is difficult due to many factors. Generally tracer techniques are used, but they measure the molecular retention time instead of the hydraulic retention time; and depending on the case, the results can be wrong. In order to contribute to solving this problem, the objective of this research was to find a trustworthy and adequate technique to determine the hydraulic retention time for a process using a very adsorbent filter bed material (peat). An overview of the hydraulic behaviour of a peat bed filter related to their particular structural composition is presented. Then, based on these characteristics, two different techniques to determine the hydraulic retention time were developed and tested. The first, an indirect modified tracing technique and, the second, a direct one which determines the volume of liquid in treatment into the filter bed through the establishment of a relation between the volume of porosity and the volume of empty spaces (or not occupied by liquid) into the filter bed. The results obtained showed that the proposed techniques gave similar results and proved adequate.