Treatment of Saline Organic Wastewater by a Submerged Anaerobic Membrane Bioreactor (SAMBR)

The aim of this thesis was to assess the potential of a Submerged Anaerobic Membrane Bioreactor (SAMBR) for the treatment of saline organic wastewater.. Firstly, it was found that anaerobic biomass can be acclimatised to salinities up to 20 g NaCl/L over a period of about 35 days during three batch feedings. Experiments were also carried out to evaluate the performance of anaerobic biomass during a sudden reduction and re-exposure to salinity; anaerobic biomass showed high performance during fluctuations in salinity. Then, SAMBRs were used for saline sewage treatment and it was found that 99% Dissolve Organic Carbon (DOC) removal could be obtained at 8 hours hydraulic retention time (HRT). Different start-up strategies and inoculation of halotolerant species into a SAMBR were investigated. In addition, the reduction of biogas sparging time caused an increase in TMP by 0.025 bar, but also an increase in effluent DOC removal and inside the SAMBR by 10% and 20%, respectively. Powdered Activated Carbon (PAC) addition resulted in a TMP decrease of 0.070 bar, and a 30% and 5% increase in DOC removal inside the SAMBR and effluent, respectively.The mechanisms of anaerobic biomass under high salinity were studied by investigating the role of compatible solutes, extracellular polysaccharides (EPS), and Archaeal microbial evolution. Glycine betaine was found to have the most positive effect on anaerobic biomass when added to medium with high salinity. This was found not only in batch experiments, but also in continuous ones using a SAMBR. The effluent composition from the SAMBR treating saline wastewater was analysed, and post treatment strategies using mainly PAC were analysed. The treatment of this effluent with 1.7 g PAC/L can lead to greater than 80% DOC removal. The treatment of wastewater with high salinity and Cr (III) in a system consisting of a SAMBR, an aerobic Memebrane Bioreactor (MBR) and a PAC column was examined. The system obtained 95% and 70% removal of Cr (III) and Chemical Oxygen Demand (COD), respectively. Using molecular techniques inside the SAMBR, species were identified that were capable of surviving in high salinity and Cr (III). In a short-period experiment, relaxation, liquid backwash and gas backwash techniques were compared and showed the superiority of gas backwashing to reduce fouling of the membrane. The specific resistances of a membrane operated for 100 days in the SAMBR showed that more than 90% of the total resistance was attributed to the biofilm cake layer, about 5-7% to the compounds attached on the membrane surface and about 3% to the membrane resistance and to the compounds in the inner pores of the membrane

Wastewater valorization by pure bacterial cultures to Extracellular Polymeric Substances (EPS) with high emulsifying potential and flocculation activities

Nowadays much effort has been devoted for the development of cost-effective and environmentally friendly processes to obtain extracellular polymeric substances (EPS) with high emulsifying and flocculation activities. The aim of this study was to evaluate the capacity of bacterial strains previously isolated from oil-contaminated areas to produce EPS with high emulsification and bioflocculant properties during cultivation in domestic and bilge wastewater and in industrial crude glycerol. A total of seven bacterial strains were screened for EPS production, from which two strains, Pseudomonas aeruginosa LVD-10 and Enterobacter sp. SW, were selected as potential EPS producers. EPS with high emulsifying capacity in olive oil (a maximum of 96.6 and 89.8% for strain SW and LVD-10, respectively) was produced using bilge wastewater as substrate. EPS with a slightly lower emulsifying capacity was obtained using crude glycerol. In addition, the flocculation activity of the EPS extracted from strains LVD-10 and SW grown on crude glycerol was considerably higher (81.6 and 73.3%, respectively) than that obtained with other substrates. This is the first study that points out that EPS with emulsifying and flocculation potential activity can be produced from bilge wastewater and crude glycerol. The production of biopolymers with broad biotechnological applications using low-cost substrates can be a means to valorise waste streams.info:eu-repo/semantics/publishedVersio

Study on the fate of per- and polyfluoroalkyl substances during thermophilic anaerobic digestion of sewage sludge and the role of granular activated carbon addition

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Chromium removal mechanisms and bacterial community in an integrated membrane bioreactor system

A wastewater with high salinity (35 g NaCl/L) and chromium (0-200 mg Cr/L) was treated with an integrated system of a submerged anaerobic membrane bioreactor (MBR), followed by an aerobic MBR and a powdered activated carbon (PAC) column. The final effluent from the system was generally below 10 mg Cr/L (95% removal), although the chemical oxygen demand removal was not high (70%), possibly because of the inhibition of anaerobic and aerobic biomass by Cr and high salinity. This is the first study that investigated the performance of an integrated system with a synthetic tannery wastewater under variations in both chromium and salinity over 100 days. Molecular techniques detected the presence of certain bacteria in the submerged anaerobic MBR that could survive under both high salinity and chromium concentrations; these findings could be valuable as these bacteria could be isolated and then bioaugmented into an MBR for the treatment of tannery wastewater. The study also examined the distribution of chromium in anaerobic biomass and determined the main chromium removal mechanisms under high salinity. After 24 h of addition, the largest quantity of chromium was removed as a precipitate and the second largest was found in the residual ash of the biomass. High salinity positively affected chromium adsorption by the biomass, but only during the first 5 min. This work is important because it has implications not only for treatment plant design but also for studies on chromium removal by biomass

In situ biogas upgrading and enhancement of anaerobic digestion of cheese whey by addition of scrap or powder zero-valent iron (ZVI)

Cheese whey is an easily biodegradable substrate with high organic matter that can be anaerobically digested to biogas; however, the process is often inhibited by excess acidification due to the presence of undissociated volatile fatty acids and requires considerable concentration of alkaline buffer. The current study investigates a new approach for biogas upgrading, and increase of total CH4 in conjunction with buffering acidification by using zero-valent iron (powder and scrap metals at concentrations 25, 50, and 100 g/L) in anaerobic granular sludge and cheese whey under mesophilic batch conditions. During the first 2 cycles (total 34 days), a high performance was found in anaerobic bottles with 25 g/L powder zero valent iron (PZVI) and 50 g/L scrap zero valent iron (SZVI) since they had a higher total CH4 production compared to anaerobic bottles free of ZVI, as well as 97% CH4 composition in produced biogas compared to 74% CH4 for anaerobic bottles free of ZVI. Under these conditions, no additional NaOH was added to anaerobic bottles with 25 g/L PZVI and 50 g/L SZVI to increase the pH and at the end of 2nd cycle the concentration of VFAs was substantially lower compared to the anaerobic bottles free of ZVI. However, no positive effects of ZVI in terms of alkaline buffer were found at the 3rd and 4th cycle probably due to ZVI inactivation outer surface layer. Based on the experimental findings (anaerobic bottles: (a) 25 g/L PZVI, (b) 50 g/L SZVI and (c) free of ZVI) an economic comparison for anaerobic digestion of cheese whey by large scale was contacted and pointed out that the best scenario was the anaerobic digestion by addition of 50 g/L SZVI, followed by anaerobic digestion free of ZVI and last was the anaerobic digestion by addition of 25 g/L PZVI. This study highlights a new proof of concept for in-situ biogas upgrading and alleviation of acidification by addition of 50 g/L SZVI or 25 g/L PZVI during anaerobic digestion of cheese whey

Compatible solute addition to biological systems treating waste/wastewater to counteract osmotic and other environmental stresses: a review

This study reviews the addition of compatible solutes to biological systems as a strategy to counteract osmolarity and other environmental stresses. At high osmolarity many microorganisms accumulate organic solutes called “compatible solutes” in order to balance osmotic pressure between the cytoplasm and the environment. These organic compounds are called compatible solutes because they can function inside the cell without the need for special adaptation of the intracellular enzymes, and also serve as protein stabilizers in the presence of high ionic strength. Moreover, the compatible solutes strategy is regularly being employed by the cell, not only under osmotic stress at high salinity, but also under other extreme environmental conditions such as low temperature, freezing, heat, starvation, dryness, recalcitrant compounds and solvent stresses. The accumulation of these solutes from the environment has energetically a lower cost than de novo synthesis. Based on this cell mechanism several studies in the field of environmental biotechnology (most of them on biological wastewater treatment) employed this strategy by exogenously adding compatible solutes to the wastewater or medium in order to alleviate environmental stress. This current paper critically reviews and evaluates these studies, and examines the future potential of this approach. In addition to this, a strategy for the successful implementation of compatible solutes in biological systems is proposed

Calcined eggshells in anaerobic digestion: Buffering acidification in AD and evaluating end products from phosphate adsorption as soil conditioners

The conversion of biowaste to a material that can improve environmental processes contributes to the circular economy. This study uses calcined eggshells as a new approach to counteract excessive acidification and alleviate low pH in anaerobic digestion. Calcined eggshells (900 °C, 30 min) addition in AD systems fed with 8 g L-1 glucose alleviated pH drop and showed substantially higher methane generation than the control. The pH value at the control was 5.63 due to the high VFAs, which severely inhibited the AD process, while after the addition of calcined eggshells, the pH was 7.13 producing significantly higher methane. Soluble CO2 had a higher adsorption affinity towards calcined eggshells than phosphates and negatively influenced the phosphate adsorption; however, this contributes to pH increase. By contrast, flushing with N2 showed high phosphate removal. Furthermore, calcined eggshells demonstrated high phosphate removal for anaerobic dewatered sludge leachates and anaerobic effluent wastewater (>78.4%) within the first 20 min. After the adsorption/precipitation of phosphate from anaerobic effluent, the solid residue positively affected plant growth for Sinapis alba and Lepidium sativum seeds. This new proof of concept contributes to the circular economy; the calcined eggshells are integrated with anaerobic digestion both in-situ for buffering acidification and ex-situ for phosphate removal and potential use as a soil conditioner

Closing the water cycle for industrial laundries: An operational performance and techno-economic evaluation of a full-scale membrane bioreactor system

To reduce the consumption of freshwater in the laundry industry, a new trend of closing the water cycle has resulted in the reuse/recycling of water. In this study, the performance of a full-scale submerged aerobic membrane bioreactor (9 m3) used to treat/reuse industrial laundry wastewater was examined over a period of 288 days. The turbidity and total solids (TS) were reduced by 99%, and the chemical oxygen demand (COD) effluent removal efficiencies were between 70% and 99%. The levels of COD removed by the membrane were significantly greater than the levels of biodegraded COD. This enabled the bioreactor to sustain COD levels that were below 100 mg/L, even during periods of low wastewater biodegradation due to bioreactor sludge. An economic evaluation of the membrane bioreactor (MBR) system showed a savings of 1.13 € per 1 m3 of water. The payback period for this system is approximately 6 years. The energy and maintenance costs represent only 5% of the total cost of the MBR system