Low-cost Wastewater Treatment Research Articles

Enhanced textile wastewater remediation in Phragmites karka-based vertical flow constructed wetlands using Phragmites-derived biochar

Vertical flow-constructed wetlands (VFCWs) are treatment systems that can be used for the phytoremediation of highly polluted textile wastewater. Using plant-derived biochar to simultaneously improve the contaminant removal performance of CWs and sustainable utilization of harvested plant biomass is an interesting proposition. The present study explored the phytoremediation potential of Phragmites karka and verified the impact of using P. karka-derived biochar as a substrate in VFCWs for the treatment of textile wastewater. For this, three types of VFCWs were designed; (i) non-vegetated (VFCW), (ii) vegetated with P. karka (VFCW–P), and (iii) vegetated with P. karka and amended with P. karka-derived biochar (VFCW-BP) and semi-batch experiments were conducted. The investigation confirmed that wetlands using biochar as substrate were more efficient than other wetlands in pollutant load reduction. The maximum pollutant removal efficiencies were recorded for VFCW-BP vis-à-vis COD (83.61%), color (77.87%), chloride (73.22%), calcium (73.52%), sodium (67.18%), and potassium (75.72%) after five days. Furthermore, biochar addition enhanced the growth conditions for wetland plants by alleviating osmotic and oxidative stresses and hence helped them to perform better while removing pollutants. The maximum reduction of various pollutant parameters was reached within 72 h, after which remediation efficiency was slowed down. The study suggests that VFCW with biochar amendment is a useful strategy for textile wastewater treatment. Because the experimental design satisfies the needs for low-cost wastewater treatment, it may find widespread applications.

Application of layered Nickel/Indium double hydroxide in the highly efficient removal of crystal violet dye from textile effluent

Worldwide freshwater demand will soon exceed supply if measures are not taken to mitigate inadequate wastewater treatment and its indiscriminate release into the environment. The textile industry is one of the largest consumers of freshwater and the third largest contributor to clean water pollution. Conventional treatment of textile effluent is inadequate and expensive. Adsorbent materials obtained from discarded solid waste precursors that contain high amounts of valuable metals can be an inexpensive way to obtain a highly efficient and low-cost wastewater treatment process. This study developed and explored a highly efficient adsorbent layered double hydroxide of Nickel and Indium (Ni/In-LDH) for the adsorption of widely used textile cationic dye, crystal violet (CV). The adsorbent material was synthesized by co-precipitation process of indium nitrate and nickel nitrate. The adsorbent material morphology and its adsorption capacity were investigated in different studies, such as the influence of pH, dosage, kinetics, isotherms, thermodynamics, ionic strength, adsorbent regeneration capacity, and interaction mechanisms of adsorption. Optimal operating conditions for Ni/In-LDH adsorption revealed maximum adsorption capacity Qmax of 570.94 mg g−1 at starting pH 8 and 60°C, which maintained approximately 75 % of the initial adsorption capacity in three successive adsorption/regeneration cycles. The experimental data fitted Pseudo first order kinetic model (PFO) and the Liu isothermal adsorption model. Thermodynamic studies indicated a spontaneous endothermic adsorption process, and a mechanism of physisorption of CV onto Ni/In-LDH substrate. After FTIR analysis of CV loaded Ni-In/LDH, electrostatic, hydrogen bonding, and n-π bonding interactions were suggested as the interaction mechanisms of adsorption. The Ni/In-LDH demonstrated excellent performance in the removal of CV dye in aqueous solutions compared to other high performing adsorbents.

Study on the enhancement of low carbon-to-nitrogen ratio urban wastewater pollutant removal efficiency by adding sulfur electron acceptors.

The effective elimination of nitrogen and phosphorus in urban sewage treatment was always hindered by the deficiency of organic carbon in the low C/N ratio wastewater. To overcome this organic-dependent barrier and investigate community changes after sulfur electron addition. In this study, we conducted a simulated urban wastewater treatment plant (WWTP) bioreactor by using sodium sulfate as an electron acceptor to explore the removal efficiency of characteristic pollutants before and after the addition of sulfur electron acceptor. In the actual operation of 90 days, the removal rate of sulfur electrons' chemical oxygen demand (COD), ammonia nitrogen, and total phosphorus (TP) with sulfur electrons increased to 94.0%, 92.1% and 74%, respectively, compared with before the addition of sulfur electron acceptor. Compared with no added sulfur(phase I), the reactor after adding sulfur electron acceptor(phase II) was demonstrated more robust in nitrogen removal in the case of low C/N influent. the effluent ammonia nitrogen concentration of the aerobic reactor in Pahse II was kept lower than 1.844 mg N / L after day 40 and the overall concentration of total phosphorus in phase II (0.35 mg P/L) was lower than that of phase I(0.76 mg P/L). The microbial community analysis indicates that Rhodanobacter, Bacteroidetes, and Thiobacillus, which were the predominant bacteria in the reactor, may play a crucial role in inorganic nitrogen removal, complex organic degradation, and autotrophic denitrification under the stress of low carbon and nitrogen ratios. This leads to the formation of a distinctive microbial community structure influenced by the sulfur electron receptor and its composition. This study contributes to further development of urban low-carbon-nitrogen ratio wastewater efficient and low-cost wastewater treatment technology.

Removal of major nutrients by sono-direct and sono-alternate current electrocoagulation process from domestic wastewater

Background: Electrocoagulation is becoming a promising eco-friendly wastewater treatment technique. It is a low-cost wastewater treatment method suitably applied for various wastewater effluent characteristics. Nevertheless, there are different kinds of electrocoagulation; comparison among them in terms of nutrient removal is investigated in the present research. This study analyzed nitrate (NO3 - ) and phosphate (PO4 3-) removal potential of the sono-alternative and direct-current electrocoagulation process. Methods: Batch reactor and sono-direct current (SDC)/sono-alternative current (SAC) electrocoagulation cell were employed to investigate NO3 - and PO4 3- removal efficiency from domestic effluents. The data gathered from laboratory experiments were analyzed using response surface methodology (RSM). ANOVA was used to examine the interaction effects of diverse parameters in terms of NO3 _ and PO4 3- removal from domestic wastewater effluents. Results: At extreme experimental conditions, the percentage of NO3 - and PO4 3- removal attained with sono-direct current electrocoagulation (SDCE) and sono-alternative current electrocoagulation (SACE) were 96.5%, 96.2% and 96.8%, 96.5, respectively. The SACE was more successful in eliminating NO3 - and PO4 3- than the SDCE process. The appearance of resistant oxide coating on the cathode and the appearance of corrosion on the anode due to oxidation processes in the case of SDCE were identified as principal factors highly affecting NO3 - and PO4 3- removal efficiency. Conclusion: With optimum process efficiency, experimental findings show that the SACE process is more capable of NO3 - and PO4 3- removal than the SDCE process.

Biofilm bioactivity affects nitrogen metabolism in a push-flow microalgae-bacteria biofilm reactor during aeration-free greywater treatment

Non-aeration microalgae-bacteria biofilm has attracted increasing interest for its application in low cost wastewater treatment. However, it is unclear the quantified biofilm characteristics dynamics and how biofilm bioactivity affects performance and nitrogen metabolisms during wastewater treatment. In this work, a push-flow microalgae-bacteria biofilm reactor (PF-MBBfR) was developed for aeration-free greywater treatment. Comparatively, organic loading at 1.27 ± 0.10 kg COD/(m3⋅d) gave the highest biofilm concentration, density, specific oxygen generation (SOGR) and consumption rates (SOCR), and pollutants removal rates. Contributed to low residual linear alkylbenzene sulfonates and bioactivity, reactor downstream showed low bacteria and protein concentrations and SOCR (12.8 mg O2/g TSS·h), but high microalgae, carbohydrate, biofilm density, SOGR (49.4 mg O2/g TSS·h) and pollutants removal rates. Dissolved organic nitrogen (DON) showed higher molecular weight, CHONS and fraction with 4 atoms of N in reactor upstream. Most of nitrogen was fixed to newly synthesized biomass during assimilation process by related functional enzymes, minor contributed to denitrification due to low N2 emission. High nitrogen assimilation by microalgae showed high SOGR, which favored efficient multiple pollutants removal and reduced DON emission. Our findings favor the practical application of PF-MBBfR based on biofilm bioactivity, enhancing efficiency and reducing DON emission for low- energy-input wastewater treatment.

Isotherm and kinetic investigations of sawdust-based biochar modified by ammonia to remove methylene blue from water

Chemical industry effluent may pose significant environmental risks to both human health and the economy if it is not properly managed. As a result, scientists and decision-makers are paying increasing attention to developing a sustainable, low-cost wastewater treatment technique. This work aims to investigate the adsorption of Methylene Blue (MB) dye present in water using biochar derived from sawdust modified by boiling in an ammonia solution (SDBA). The properties of SDBA were characterized by BET, SEM, XRD, BJH, FT-IR, DTA, EDX and TGA analyses. The presence of –OH and –NH groups in SDBA was confirmed by FTIR, which proved that the NH4OH treatment of biochar successfully added nitrogen groups on its surface. The influence of pH (2 to 12), MB dye initial concentration (20 to 120 mg/L), adsorbent dosage (0.5 to 4.0 g/L) and contact time (0 to 180 min) on the adsorption process has been investigated. The adsorption of MB dye is more favorable at basic pH, with optimum adsorption at pH 8. Using a starting concentration of 20 mg/L of MB dye and a 4.0 g/L SDBA dose, the maximum percent clearance of MB dye was 99.94%. Experimental results were fitted to the Freundlich (FIM), Tempkin (TIM) and Langmuir (LIM) isotherm models (IMs). The FIM fitted the equilibrium data well, with a 643.74 mg/g Qm. Various error function models were used to test the data obtained from IMs. According to Error Function results, experimental data showed that it fits better for LIM and FIM. Kinetic studies indicated that the MB dye adsorption procedure followed pseudo-second-order (PSOM) kinetics based on film diffusion (FDM), pseudo-first-order (PFOM) and intra-particle diffusion models (IPDM). MB dye sorption on the SDBA involved electrostatic interaction, surface participation, hydrogen bond and π–π interactions. The adsorption mechanism of MB dye by SDBA was proposed as physical adsorption via the electrostatic attraction process. SDBA is an effective adsorbent in removing MB dye from water. Six adsorption–desorption cycles of the MB dye were run through the regeneration of SDBA with only a minimal amount of adsorption capacity loss, demonstrating the reusability of manufactured SDBA.

Iron azaphthalocyanine electrocatalysts for enhancing oxygen reduction reactions under neutral conditions and power density in microbial fuel cells

Highly catalytic cathodes for oxygen reduction reactions under neutral conditions allow major improvement in the power output of microbial fuel cells (MFCs). This work reports iron azaphthalocyanine impregnated into oxidized multi-walled carbon nanotubes to form a molecularly synthesized non-precious metal electrocatalyst. The synthesized catalyst was characterized using a rotating ring and disk electrode in a neutral medium (pH = 7.4) and exhibited a four-electron transfer pathway. When incorporated as a cathode in a two-chamber MFC assembly, the electrocatalyst achieved a power density of 1.54 W/m2 and a current density of 10.7 A/m2, which was 27 % higher than a commercial platinum‑carbon catalyst. In addition, the MFC loading of the molecular catalysts reached over 80 % COD removal efficiency. This work demonstrates that the use of an electrocatalyst based on the FeN4 structure and efficient electron-withdrawing nitrogen improves the application of MFCs in low-cost wastewater treatment and the generation of electricity from wastewater.

Design and Development of a Low-Cost Wastewater Treatment Plant for the NMCE Campus

Abstract: The characteristics and quantity of wastewater are required to get the correct treatment system for wastewater reuse in the NMCE campus. Water is an essential commodity of society. The water availability in NMCE during the summer season is limited, and the wastewater disposal system in NMCE is not methodical. It is directly discharged into open land; therefore, it must design and develop a wastewater treatment plant for the NMCE campus. Wastewater treatment by constructed wetlands is emerging as the low-cost alternative method involving plant species for sewage treatment. The present study will address the design of a wastewater treatment plant for the NMCE campus.

Removal of copper and zinc in metal working fluid using coconut composite filter media

Metal working fluid industry is the major contributing sources of heavy metals. Their multiple industrial, domestic, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Filtration technology is widely used to remove contaminants such as heavy metals because it is a low-cost wastewater treatment device that uses physical methods that are simple and effective. In this study, coconut composite activated carbon (CCAC) filter media has been explored for its adsorption abilities towards copper and zinc solutions from metal working fluids. The characteristic of CCAC was investigated using XRF analyser, SEM and FTIR analysis. This study described the performance of fixed-bed column filtration by using CCAC as the filter media under the effect of various bed heights (10,30,50 cm) and initial concentration of copper and zinc (10 and 20 mg/L) to assess the breakthrough curve. The results show that the CCAC surface is not smooth and porous, with many channels. It is connected to hydrogen linked, O-H and contains the highest value composition in MgCO3 and CaCO3, which enhances metal precipitation removal of heavy metals. From the fixed-bed column study, the column with an initial copper and zinc concentration of 10mg/L and a bed height of 50 cm performed well in removing copper and zinc from synthetic copper and zinc solutions. The breakthrough and exhaustion times were less than 30 minutes and 3660 minutes for copper and zinc were less than 30 minutes and 3420 minutes respectively. The longer the lifespan of filter media, the better the filter media for heavy metal treatment. In conclusion, CCAC filter media was used as an alternative to the existing wastewater treatment process to remove copper and zinc from metal working fluids. It also can be applied in the current filtration system, especially for industrial Wastewater Treatment Plant (WWTP).

Efficiency of lagoon-based municipal wastewater treatment in removing microplastics

Municipal wastewater treatment plants act as a sink, but also are a source of microplastics in the environment. A conventional wastewater lagoon system and an activated sludge (AS)-lagoon system in Victoria (Australia) were investigated through a two-year sampling program to understand the fate and transport of MP in such treatment processes. The abundance (>25 μm) and characteristics (size, shape, and colour) of the microplastics present in the various wastewater streams were determined. The mean values of MP in the influent of the two plants were 55.3 ± 38.4 and 42.5 ± 20.1 MP/L, respectively. The dominant MP size of influent and final effluent was <500 μm, with 25–200 μm accounting for >65 % of the total MP; synthetic fibres were the dominant MP in all wastewater streams. Influent MP concentration was significantly higher in summer than in other seasons for both systems, which was related to the lower plant inflow due to less stormwater entering the sewer during summer. The promising MP removal capability of the lagoon system (97 %) was attributed to its lengthy wastewater detention time (total HRT >250 days, including the storage lagoons) that would allow effective separation of MP from the water column via various physical and biological pathways. For the AS-lagoon system, the high MP reduction efficiency (98.4 %) was attributed to the post-secondary treatment of the wastewater with the lagoon system, in which MP was further removed during the month-long detention in the lagoons. The results indicated the potential of such low-energy and low-cost wastewater treatment systems for MP control.

Antarctic granite rocks as wastewater surfactant degradation catalysts

Antarctica seawater surrounding research stations has been impacted by antibiotics, formaldehydes, surfactants, heavy metals, sunscreen chemicals, and coliforms. The removal of surfactants from water is challenging since biological approaches are ineffective at mineralizing organic molecules. To evaluate the effectiveness of an advanced oxidation process (AOP) on the degradation of surfactants at the “Pedro Vicente Maldonado” research station of Ecuador, the performance of Antarctic granite rocks as catalysts and hydrogen peroxide (H2O2) as an oxidant was researched. Following the coagulation-flocculation process, the AOP reduced the concentration of surfactant by 90 %, from 19.50 mg/L to 0.97 mg/L. This short communication summarizes initial research on a low-cost wastewater treatment that could be used to degrade surfactants after coagulation-flocculation processes.

Aeration-free greywater treatment in a self-sustaining oxygenic photobiofilm: Performance and mechanisms

Microalgal-bacteria symbiosis system shows great potential in efficient carbon and nitrogen recovery during low-cost wastewater treatment. Poor self-flocculation of microalgal hinders the wide practical application of the symbiosis process. This study constructed a bench-scale self-sustaining microalgal-bacterial biofilm reactor (MBBfR) for simultaneous and efficient removal of organics and nitrogen (N) during greywater treatment. Results showed that increasing organics loading rate (OLR) from 253.3 ± 10.1 to 1564.5 ± 10.6 g/(m2·d) led to continuous rose of biomass concentration, but microalgal proportion initially decreased and then increased to 60 %; much higher OLR led to the declined concentration of both microalgae and bacteria. Multifarious functional groups in the symbiotic biofilm enabled pollutants adsorption and accumulation in the biofilm, which favored its continuous biodegradation. OLR of 1564.5 ± 10.6 g COD/(m2·d) achieved the maximum removal efficiency of chemical oxygen demand (COD), linear alkylbenzene sulfonates (LAS), NH4+-N and total N at 93.3, 97.6, 99.6 and 85.7 %, respectively. The related genus and enzymes functional for metabolisms of ammonia, nitrate and organic N, and LAS biodegradation enabled the simultaneous removal of organics and N in the MBBfR. Key is that microalgal contributes to oxygen supplying, pollutants adsorption and the assimilation of inorganic carbon and nitrogen; bacteria achieve pollutants biosorption and biodegradation.

Application of a new baffled horizontal flow constructed wetland-filter unit (BHFCW-FU) for treatment and reuse of petrochemical industry wastewater

The shortage of water resources and generation of large quantum of wastewater has posed a significant concern to the environment and public health. Recent research on wastewater treatment has started to focus on reusing wastewater for different activities to reduce the stress on natural water resources. Constructed wetland (CWs) is a low-cost wastewater treatment option. However, some drawbacks include large areal requirements and the need for tertiary treatment units for reusable effluent. In this study, a novel composite baffled horizontal flow CW filter unit (BHFCW-FU) was developed to overcome the drawbacks of the conventional CW. The BHFCW-FU planted with Chrysopogon zizanioides provided a nine times longer flow path, and the adjoined variable depth dual media filter reduced the total area requirement and served as a polishing unit. On average, the BHFCW-FU with horizontal sub-surface flow regime could efficiently remove around 93.93%, 87.20%, and 66.25% of turbidity, phenol, and COD, respectively, from real petrochemical wastewater (initial turbidity: 29.6 NTU, phenol: 4.52 mg/L, and COD: 381 mg/L) and rendered the effluent quality reusable for irrigation, industrial, and other environmental purposes. In synthetic wastewater (initial turbidity: 754 NTU, phenol: 10.87 mg/L, and COD: 1691 mg/L), the removal efficiency of turbidity, phenol, and COD were 99.50%, 93.73%, and 87.05%, respectively. In-depth substrate characterization was done to study the removal mechanism. The developed BHFCW-FU required less space and maintenance, provided reusable effluent, and overcame the drawbacks of conventional CWs. Hence, it may show immense potential as an effective wastewater treatment.

An Overview of Microbial Fuel Cells within Constructed Wetland for Simultaneous Nutrient Removal and Power Generation

Water, energy, and food are indispensable for sustainable economic development. Despite nutrients, especially phosphorus and nitrogen, being essential for plant growth and thus food supplies, those present in wastewater are considered an environmental burden. While microbial fuel cells (MFCs) are receiving much interest, combining wastewater treatment with an MFC has emerged as an option for low-cost wastewater treatment. Among others, a constructed wetland (CW) coupled with an MFC (CW-MFC) has the potential to provide a low carbon footprint and low-energy wastewater treatment, as well as nutrient and energy recovery from wastewater. Findings from this review show that the organic and nutrient removal and power generation by the integrated CW-MFC systems are affected by a number of factors including the organic loading rate, hydraulic retention time, system design, plant species, dissolved oxygen, substrate/media type, influent feeding mode, electrode materials and spacing, and external resistance. This review aims to summarize the current state of the CW-MFC and related technologies with particular emphasis on organic and nutrient removal, as well as on the bioenergy recovery from different wastewaters. Despite the benefits that these technologies can offer, the interactive mechanisms between the CW and MFC in the integrated system are still unclear. Further research is needed to fully understand the CW-MFC and related systems. The results of this work provide not only an overview and insight into existing knowledge but also the future direction of the CW-MFC technologies.

Constructed Wetland for Sustainable and Low-Cost Wastewater Treatment: Review Article

There is a growing need for more sustainable wastewater treatment technologies to provide non-conventional water sources. Constructed Wetland systems (CW) are viewed as a low-cost treatment technology with proven treatment efficiency. CWS can treat a variety of contaminants using low energy and natural systems by altering various design parameters. There are two configuration types of constructed wetlands: vertical (VF) and horizontal flow CW (HF). Both configurations have been widely adopted in both large and pilot scale studies with proven records of reasonable wastewater treatment efficiency. The current article reviews the recent development of CW technology and highlights the main achievements and successful applications for wastewater treatment at various locations. The review has indicated that a considerable removal efficiency is attained while using engineered CW systems with variable treatment rates for various pollutants. The treatment efficiency is a function of various parameters including wastewater type, scale dimensions, applied plant and the retention time. The review compared the treatment efficiency for both VF and HF and has revealed that various removal rates of BOD, COD, TSS, TN, TP and NH₄ was attained using both configurations. Yet, the removal efficiency in the case of VF was slightly higher compared with the HF with an average treatment level of 77% and 68% was achieved in both systems, respectively. The review revealed that the CW is an effective and sustainable technology for wastewater treatment with the initial influent level, microbial biofilm, detention time, plant species and configuration among the most dominating parameters that are directly controlling the removal rates.

Red mud-based polyaluminium ferric chloride flocculant: Preparation, characterisation, and flocculation performance

In this study, red mud was used as a raw material to extract Al and Fe using hydrochloric acid. A highly efficient polyaluminium ferric chloride (PAFC) flocculant was prepared by adjusting the pH of a leaching solution, the molar ratio of Al to Fe, and the polymerisation temperature. The effects of synthesis and flocculation conditions on the flocculation performance of aged landfill leachate were investigated. The results confirmed that PAFC flocculant prepared at a polymerisation pH of 2.5, Al/Fe molar ratio of 8, and polymerisation​ temperature of 70 °C had the optimum effect. The effect of PAFC and commercial polyaluminium ferric chloride flocculants used under different flocculation conditions were compared. The chemical oxygen demand, UV 254 , chroma, total organic carbon, and PAFC settlement height at a flocculant concentration of 1.2 g/L and solution pH of 6 were 72.2%, 79.2%, 82.9%, 82.6%, and 9.5 cm (within 90 min), respectively. The PAFC performed excellently at flocculation and can be used as a simple and potentially low-cost wastewater treatment agent in industrial applications. • Red mud was used to synthesise polyaluminium ferric chloride (PAFC) flocculant. • The COD and TOC of PAFC to landfill leachate were 72.2% and 82.6%, respectively. • PAFC have advantages over commercial PAFC in settlement velocity and TOC removal efficiency.

White carbon black wastewater treatment by electrodialysis: Salt separation, silicon sol transporting and wastewater recycling

White carbon black (WCB) as an important silica product has been widely used in many industrial processes. At present, precipitation method is commonly adopted for WCB production, in which a large amount of wastewater containing sodium sulfate and silica is produced. Therefore, it is important and urgent to develop an efficient, low-cost wastewater treatment process, which could extract sodium sulfate from wastewater as value-added byproducts and then recycle this wastewater back to WCB process. In this study, electrodialysis (ED) method, as a proven salt-separation technology, was used to treat WCB wastewater. The existence of silica in the wastewater brings more difficulties for its ED treatment. Firstly, to evaluate ED performance on treating WCB wastewater, the effects of applied voltage, flow rate and initial volume ratio on the overall current efficiency (η), recovery ratio (R), residual rate (γ) and concentration ratio (ω) were investigated. The results show that under the optimized conditions, the highest recovery ratio of Na2SO4 could reach 86.45%, the lowest overall residual rate of SiO2 could go down to 2.69%, and the dilute solution could achieve the reuse standard of waste water. Secondly, the influence of silica on ED performance was investigated. It is found that only about 5.91% of silica in wastewater was transporting from dilute solution to concentrated solution under the optimized conditions. The SEM images of ED membrane indicate that after ED experiments some SiO2 particles adhered to the surface of ion exchange membrane, which would not affect ED normal performance in a short term. These results illustrate that ED is an effective, low energy-cost and reliable process to treat WCB wastewater.

Submerged anaerobic membrane bioreactor applied for mainstream municipal wastewater treatment at a low temperature: Sludge yield, energy balance and membrane filtration behaviors

The anaerobic membrane bioreactor (AnMBR) has potential as a low-cost wastewater treatment process with the benefit of energy production. However, to ensure satisfactory treatment performance, an AnMBR is operated at a relatively high temperature currently. Research focused on the operation of the AnMBR at low temperature is significant since the energy required for heating is an impediment to the application of AnMBRs for municipal wastewater treatment. Hence, in this study, a constant low-temperature (15 °C) AnMBR was evaluated for the treatment of real municipal wastewater with hydraulic retention times (HRTs) in the range of 6–24 h. During the long-term experiment, a chemical oxygen demand (COD) removal efficiency of approximately 90.5% was obtained with a sludge yield below 0.13 g-VSS/g-CODrem at HRTs of 16 and 24 h. The amount of energy generated was theoretically calculated based on biogas production, with a high of 0.62 kWh/t. The energy balance analysis showed that the AnMBR process can be energy positive under the optimal operational conditions investigated. Membrane filtration performed well during operation at 15 °C with HRTs ranging between 12 and 24 h, while it was compromised at the extremely short HRT of 6 h. In this study, the effectiveness of optimizing the conditions on the performance of the AnMBR operating at low temperature was confirmed, along with the potential for energy recoverability under those conditions.

Sustainable microalgal biomass production in food industry wastewater for low-cost biorefinery products: a review.

Microalgae are recognized as cell factories enriched with biochemicals suitable as feedstock for bio-energy, food, feed, pharmaceuticals, and nutraceuticals applications. The industrial application of microalgae is challenging due to hurdles associated with mass cultivation and biomass recovery. The scale-up production of microalgal biomass in freshwater is not a sustainable solution due to the projected increase of freshwater demands in the coming years. Microalgae cultivation in wastewater is encouraged in recent years for sustainable bioeconomy from biorefinery processes. Wastewater from the food industry is a less-toxic growth medium for microalgal biomass production. Traditional wastewater treatment and management processes are expensive; hence it is highly relevant to use low-cost wastewater treatment processes with revenue generation through different products. Microalgae are accepted as potential biocatalysts for the bioremediation of wastewater. Microalgae based purification of wastewater technology could be a universal alternative solution for the recovery of resources from wastewater for low-cost biomass feedstock for industry. This review highlights the importance of microalgal biomass production in food processing wastewater, their characteristics, and different microalgal cultivation methods, followed by nutrient absorption mechanisms. Towards the end of the review, different microalgae biomass harvesting processes with biorefinery products, and void gaps that tend to hinder the biomass production with future perspectives will be intended. Thus, the review could claim to be valuable for sustainable microalgae biomass production for eco-friendly bioproduct conversions.Graphical abstract

Performance Upgrading Evaluation of the Anaerobic Baffled Reactor by Integrating Aerobic Media Filter for Municipal Wastewater Treatment

Background &amp; Aims of the Study: Anaerobic baffled reactor (ABR) is one of the low-cost wastewater treatment systems; however, it has some limitations, such as insufficient standard nutrient outflow. Accordingly, it should be studied and developed. This research aims to determine the efficiency of a five-sectional reactor pilot and to upgrade it with an integrated aerated media filter in the reactor (integrated reactor) for municipal wastewater treatment. Materials and Methods: This study was performed on a laboratory scale with field conditions in the Khoy City wastewater treatment plant. The ABR reactor operated for 270 days with a hydraulic retention time (HRT) of 48, 36, 24, and 18 hours, respectively. The Integrated anaerobic baffled reactor (IABR) was operated for 35 days with 24 hours of HRT, i.e., aeration time of 5 hours. The reactors were fed in line from the inflowing wastewater to the treatment plant. A 24-hour combined sampling was performed 224 times from the inflow and outflow of the system, and volatile suspended solids, total kjeldahl nitrogen (TKN), total phosphorus (TP), biochemical oxygen demand (BOD), chemical oxygen demand (COD), and Total Suspended Solids (TSS) parameters were measured and compared with the effluent disposal standard. Results: The launch of ABR lasted 105 days, and its helpful operation lasted 200 days. In 18 to 48 hours, the reactor removed 79% to 91% of COD, 9% to 20% of TKN, 19% to 30% of phosphorus, and 89% to 94% of TSS. The IABR reached the effluent disposal standard in terms of TSS, BOD, COD, and phosphorus under 24 hours HRT, i.e., aeration time of 5 hours, and increased the COD removal efficiency by 6% compared to ABR under 24 hours HRT and the same conditions. Conclusion: By integrating the final aerobic media filter in ABR while reducing the required HRT by 50%, its efficiency in achieving the effluent disposal standards increased compared to ABR. Therefore, this system can be used to treat municipal wastewater.