In the present study, we investigated the role of the constructed wetlands (CWs) integration with the bioelectrochemical system (BES), which can concurrently treat the wastewater effectively with energy recovery. This CWs integrated system utilizes NH4+-N (96.66%), NO3- -N (83.09%), PO43- -P (91.04%) and SO42- (83.98%) to enable effective pollutants removal from sewage wastewater. Nitrite accumulation was not observed in the systems with applied voltage >15 mV and MFCs-ME. The ME-30-CWs system favour all the pollutants removals, except ammonia. The average, power density and the current density of 1.723 mWm−2 and 5.423 mAm−2 were recorded in MFC-CWs during wastewater treatment. The waterborne diseases causing Shigella sp. and Salmonella sp. were significantly eliminated in the CWs integrated system. The promising potential of CWs, bioelectrochemical technology can be an effective alternative to water-energy nexus for waste stream applications.

In recent decades, academia has elaborated a wide range of technological solutions to recover water, energy, fertiliser and other products from municipal wastewater treatment plants. Drivers for this work range from low resource recovery potential and cost effectiveness, to the high energy demands and large environmental footprints of current treatment-plant designs. However, only a few technologies have been implemented and a shift from wastewater treatment plants towards water resource facilities still seems far away. This critical review aims to inform decision-makers in water management utilities about the vast technical possibilities and market supply potentials, as well as the bottlenecks, related to the design or redesign of a municipal wastewater treatment process from a resource recovery perspective. Information and data have been extracted from literature to provide a holistic overview of this growing research field. First, reviewed data is used to calculate the potential of 11 resources recoverable from municipal wastewater treatment plants to supply national resource consumption. Depending on the resource, the supply potential may vary greatly. Second, resource recovery technologies investigated in academia are reviewed comprehensively and critically. The third section of the review identifies nine non-technical bottlenecks mentioned in literature that have to be overcome to successfully implement these technologies into wastewater treatment process designs. The bottlenecks are related to economics and value chain development, environment and health, and society and policy issues. Considering market potentials, technological innovations, and addressing potential bottlenecks early in the planning and process design phase, may facilitate the design and integration of water resource facilities and contribute to more circular urban water management practices.

A novel palm fiber biofilm electrode reactor (PBER) was developed, and its denitrification mechanism was analyzed by investigating denitrification performance, extracellular polymeric substances (EPS) and microbial community. The results showed that palm fiber was a stable and efficient electrode embedding material. Almost 100% nitrate removal efficiency was achieved at 250 mA/m2 with rarely accumulation of nitrite and ammonium. Moreover, a lower energy consumption of 3.84×10-3 kWh/g NO- 3-N was obtained. It was confirmed that nitrate could be reduced by extracellular electron transfer through fulvic acid-like and humic acid-like substances in EPS. And EPS promoted biofilm stability and microbial activity at optimal current density. Furthermore, the hydrogen autotrophic denitrifying and electroactive bacterium were significantly enriched at 250 mA/m2. This study proposed an efficient BER for nitrate-contaminated wastewater treatment and provided an approach for the evaluation of denitrification mechanism in bioelectrochemical systems.

Supramolecular solvents (SUPRAS) were investigated for the recovery of bioactives from coffee wastewater (CWW), an abundant residue in the wet and semi-wet processing methods of coffee beans. SUPRAS were made up of hexagonal inverted aggregates of hexanol or decanoic acid and were spontaneously produced in the wastewater through self-assembly processes. SUPRAS components were food authorized ingredients this facilitating future industrial applicability. Under passive extraction (energy-less procedure), caffeine was recovered with a yield of 54 to 65 mg per liter of wastewater. SUPRAS extracts showed good antioxidant capacity (up to 53% ABTS•+) and were stable for at least 2 months in the range of temperatures investigated (4-24 ºC) for the preservation of bioactives. Additionally, the SUPRAS-based extraction of bioactives improved substantially some wastewater quality parameters (e.g. BOD, total suspended solids and conductivity), so this process also helped to purify wastewater before dumping it to surface waters.

Hexavalent chromium [Cr(VI)] is highly water soluble and their compounds act as strong oxidizing agent that easily reacts with human organs which leads to the various carcinogenic diseases. Cr(VI) removal is very important to provide safe drinking water. Hence, this research work targets in Cr(VI) removal using sustainable material like triazine assisted micro-porous covalent organic polymer enfolded alginate biocomposite beads (TCOP@Alg) were synthesized by hydrothermal method. To find the physico-chemical properties of TCOP@Alg biocomposite beads, FTIR, PXRD, SEM, XPS, EDAX, BET and mapping analysis were scrutinized. The surface area of TCOP@Alg biocomposite beads was found to be 292 m2/g and shows the excellent sorption SC of 42.89 mg/g. The sorption data of Cr(VI) removal onto TCOP@Alg biocomposite beads is well correlated with various isotherms and kinetic models. The thermodynamic equilibrium values represented that Cr(VI) sorption onto TCOP@Alg biocomposite beads were to follow endothermic and spontaneous. In addition, TCOP@Alg hybrid biocomposite bead can be efficiently regenerated upto three cycles using 0.1 M NaOH. TCOP@Alg biocomposite beads can be employed as potential sorbent for Cr(VI) removal from Cr(VI) contaminated ground water.

This study investigated the adsorption behaviors of chlorate and chlorite by MIEX resin, and the optimal conditions of removal rate using the response surface methodology. Chemical properties of the solution, such as pH, coexistent anions and ion strength, has great influence on adsorption of chlorate and chlorite. When pH tends to neutral, the removal rate of chlorate and chlorite on MIEX is the best. Sulfate radical has a damaging influence on the adsorption of chlorate and chlorite on MIEX for the low adsorption capacity. The initial adsorption kinetics of chlorate and chlorite adsorption on MIEX follows the intra-particle diffusion-controlled adsorption. Box-Behnken design method is successfully used to establish a quadratic polynomial mode for predicting the removal efficiency of chlorate and chlorite, which is composed of three variables (absorbent dosage, reaction time and initial concentration). According to the results, the adsorbent dosage had a strong interaction with chlorate or chlorite concentration and reaction time, which has a significant impact on the optimization of chlorate and chlorite removal process by MIEX. From the FTIR, the adsorption mechanisms is anion exchange in the chlorate and chlorite.

Recently, mainstream anaerobic ammonium oxidation (anammox) has attracted extensive attentions due to its energy-neutral advantages. The inhibition of nitrite oxidizing bacteria is a key factor to guarantee the occurrence of anammox process, which is usually achieved by controlling the aeration condition. This study integrates the gel entrapment technique with traditional biofilm (abbreviated as BSgel system) to realize a simultaneous partial nitrification, anammox and denitrification (SNAD) process. The anammox biofilm on the surface of carrier was covered by the gel with entrapped activated suspended sludge. The results show that SNAD process successfully took place in BSgel, while the traditional hybrid system of biofilm and suspended sludge only yielded nitrification process. Furthermore, the hindrance effect of high organic matter concentration (up to 100 mg·L-1 COD) was weakened and the specific total inorganic nitrogen (TIN) removal rate arrived at 57 mgN·(gVSS·d)-1 in BSgel. However, the low temperature (15°C) mitigated the nitrogen removal potential. Besides, the BSgel system possessed the reactivation ratio of nitrogen removal ability at 68% after preservation under -20°C for one month. The high-throughput sequencing analysis indicates that the BSgel system combined the common microbial community characteristics of both biofilm and suspended sludge. The dominant anammox group belonged to Candidatus Kuenenia. Finally, the numerical modelling predicts the profiles of microbial and nutrient profiles in gel film of partially entrapping and fully entrapping BSgel systems, indicating that the fully entrapping pattern outperformed. Overall, our findings support that the BSgel system facilitates the SNAD process under mainstream conditions within a short time.

The present review highlights the different types of nano ferrites and their surface modified composites as an alternative adsorbent in waste water treatment. The need of surface modification of nano ferrites with different surface modification methods are highlighted broadly. The general mechanism of adsorption of different types of pollutants with surface modified nano ferrites has been reflected comprehensively. The regeneration study of nano ferrites and their composites using different types of desorbing agents has been reported. The main thrust of the review is to provide recent information about the most important features of different nano ferrites and their composites. The present study highlights the future areas of research for waste water treatment.

The aerobic granular sludge process is an alternative to the conventional activated sludge process adopted in water resource recovery facilities. This study presents the first independent assessment of aerobic granular sludge technology in terms of oxygen transfer efficiency and nutrient removal performance. Using off-gas testing, a full-depth pilot reactor with granular biomass was compared to an identical reactor with floccular biomass. The granular process presented lower oxygen transfer efficiency than the floccular sludge (2.3%/m vs. 3.2%/m, respectively). The granular sludge was also tested at different operating conditions in order to address potential retrofitting for existing aeration basins. With regard to oxygen transfer efficiency, the experiments show a marginal improvement at lower MLSS (0.2%/m) and at medium side-water-depth (0.3%/m). Satisfactory effluent water quality levels, in terms of nitrogen and phosphorous removal, were obtained for the granular sludge except for decreased MLSS conditions during which the nitrification/denitrification process was highly penalized.