Chromate and selenate hydrocalumite solid solutions and their applications in waste treatment

Hydrocalumite, a calcium aluminate hydrate phase, consists of positively-charged structure units, and is therefore an ideal candidate for accommodating anionic contaminants. In this study, a series of batch experiments was carried out to examine the uptake of chromate and selenate by hydrocalumite. To determine the uptake capacity and long-term stability, hydrocalumite solid solutions between chromate/selenate and hydroxyl were synthesized over a reaction time of more than one year. At a ratio of water to initial solids added (CaAI₂O₄+CaO) of 75:1, the maximum uptake capacities were over 77 and 114 g/kg for Cr and Se, respectively. These values are very close to the theoretical uptake capacities of chromate and selenate hydrocalumite end members (81 and 118 g/kg, respectively). The oxyanion removal efficiency from solution was above 95%. Due to the high uptake capacity and anion removal efficiency of hydrocalumites, their application in wastewater treatment is promising. Hydrocalumites are also important hydration products of cementitious materials, the long-term stability of these phases is of significance for application in solidification/stabilization technology.

     

Laccase grafted membranes for advanced water filtration systems: a green approach to water purification technology

Purpose: Conventional wastewater treatment technologies are not good enough to completely remove all endocrine disrupting compounds (EDCs) from the water. Membrane separation systems have emerged as an attractive alternative to conventional clarification processes for waste and drinking water. Coupling of a membrane separation process with an enzymatic reaction has opened up new avenues to further enhance the quality of water. This review article deliberates the feasibility of implementing enzymatic membrane reactors has been deliberated.

Materials and methods: A comprehensive study of conventional water treatment technologies was carried out and their shortcomings were pointed out. Research findings from the leading groups working on enzyme grafted membrane based water purification were summarized. This review also comprehends the patent documents pertinent to the technology of enzyme grafted membranes for water purification.

Results: Immobilization of an enzyme on a membrane improves the performance of membrane filtration, and processes for the treatment of polluted water. Research has started exploring the potential for laccase enzymes because it can catalyze the oxidation of a wide range of substrates, structurally comparable to EDCs, by a radical-catalyzed reaction mechanism, with corresponding reduction of oxygen to water in an electron transfer process. Further, in the presence of certain mediators, the substrate range of laccases can be further enhanced to non-aromatic substrates.

Conclusions: Removal of EDCs by laccase cross-linked enzyme aggregates in fixed-bed reactors or fluidized-bed reactors and laccase immobilized ultrafiltration (LIUF) membranes are proving their worth in water purification technology. The major operational issues with the use of LIUF membranes are enzyme instability in real wastewater and membrane fouling. In view of the above-stated characteristics, laccases are considered as the most promising enzyme for a greener and less expensive water purification technology.     

Floating treatment wetlands as biological buoyant filters for wastewater reclamation

Abstract

Floating treatment wetlands (FTWs) are an innovative product of ecological engineering that can play a promising role in wastewater treatment. It provides low-cost, eco-friendly, and sustainable solutions for the treatment of wastewater, particularly in regions with economic constraints. Generally, FTWs comprise rooted plants that grow on the surface of water with their roots extending down into the pelagic zone rather than being embedded into the sediments. This drooping structure helps develop (1) a hydraulic flow between the root network and the bottom of the treatment system and (2) a large biologically active surface area for the physical entrapment (filtration) of contaminants, as well as their biochemical transformation and degradation. Furthermore, the rooted network allows proliferation of microorganisms that form biofilms and enhance pollutant degradation while promoting plant growth. The augmentation of bacteria in FTWs has been proven to be the most effective approach for reclamation of wastewater. This article discusses the operational parameters of FTWs for maximal remediation of wastewater and highlights the importance of plant-bacteria partnerships in a typical FTW system for enhanced cleanup of wastewater. We propose that this technology is preferable over other methods that require high energy, costs, and area to install or operate machinery.     

Recycling of aquaculture wastewater using charcoal based constructed wetlands

Abstract

The competitive demand for water makes it a scarce resource for agricultural use. This necessitates wastewater reuse for irrigation and any other agricultural purpose, especially in developing countries where treatment of wastewaters is not a priority. The aim of this study was to evaluate the performance of a charcoal-based constructed wetland (CBCW) in treating aquaculture wastewater. Aquaculture wastewater from a Research Fishpond Farm was treated in a CBCW planted with Sacciolepsis africana and Commelina cyannae for 5?days retention time. Raw wastewater and the treated wastewater from the constructed wetland (CW) was sampled and the physicochemical parameters determined. The performance of the CW in treating aquaculture wastewater was conducted. The result showed that the CBCW was capable of removing 50% TSS, 88% COD, 93% BOD_5, and 100% nitrate nitrogen. The pH and DO of the wastewater before treatment and after treatment ranged from 6.68 to 6.91 and 4.13 to 6.30?mg/l, respectively. Thus, CWs have great potential for the treatment of aquaculture wastewater and prevention of environmental degradation through wastewater treatment, thereby solving the problem of water scarcity for agriculture for optimum food production.     

Membrane biofouling behaviors at cold temperatures in pilot-scale hollow fiber membrane bioreactors with quorum quenching

Abstract

In this study, the seasonality of the biofouling behavior of pilot-scale membrane bioreactors (MBRs) run in parallel with vacant sheets and quorum quenching (QQ) sheets using real municipal wastewater was investigated. QQ media delayed fouling, but low temperatures caused severe biofouling. The greater amount of extracellular polymeric substances (EPSs) produced in cold weather was responsible for the faster biofouling of a membrane, even with QQ media. There were significant negative relationships between EPS levels and water temperature. Cold weather was detrimental to the degradation of quorum sensing signal molecules by QQ sheets, whose activity was restored with a higher dose of QQ bacteria. The QQ bacteria in the sheets experienced a slight loss in activity during the early stage of the field test, but survived in the pilot-scale MBR fed with real wastewater. There were no significant discrepancies in treatment efficiency among conventional, vacant, and QQ MBRs.     

Constructed Wetlands for Tannery Wastewater Treatment in Portugal: Ten Years of Experience

Wastewaters from tannery industry are complex in composition and providing adequate treatment can be difficult. Constructed wetlands (CW) are regarded as an alternative treatment to the conventional biological systems, as a developing cost-effective and environmentally friendly phytoremediation technology. The present review compiles and integrates information on CWs technology for the needs of the tannery sector. The following issues arise as crucial for the implementation of such systems, namely i) an accurate wastewater characterization and an effective pretreatment before reaching the CW, ii) choosing the plants species better adapted to the imposed conditions, iii) substrate selection and iv) range of organic loadings applied. The examples practiced in Portugal give indication that horizontal subsurface flow systems, with expanded clay media, are a suitable option to be considered when dealing with high organic loading tannery wastewater (up to c.a. 3800 kgCODha^?1d^?1), being resilient to a wide range of hydraulic variations. Plants such as Phragmites and Typha have shown to be adequate for tannery wastewater depuration, with Arundo donax proving resilient to high salinity wastewaters. The flexibility of implementation allows the CW to be adapted to different sites with different configurations, being suitable as main secondary or tertiary treatment stage.     

Recent development of advanced biotechnology for wastewater treatment

Abstract

The importance of highly efficient wastewater treatment is evident from aggravated water crises. With the development of green technology, wastewater treatment is required in an eco-friendly manner. Biotechnology is a promising solution to address this problem, including treatment and monitoring processes. The main directions and differences in biotreatment process are related to the surrounding environmental conditions, biological processes, and the type of microorganisms. It is significant to find suitable biotreatment methods to meet the specific requirements for practical situations. In this review, we first provide a comprehensive overview of optimized biotreatment processes for treating wastewater during different conditions. Both the advantages and disadvantages of these biotechnologies are discussed at length, along with their application scope. Then, we elaborated on recent developments of advanced biosensors (i.e. optical, electrochemical, and other biosensors) for monitoring processes. Finally, we discuss the limitations and perspectives of biological methods and biosensors applied in wastewater treatment. Overall, this review aims to project a rapid developmental path showing a broad vision of recent biotechnologies, applications, challenges, and opportunities for scholars in biotechnological fields for “green” wastewater treatment.     

Environmental improvement of lead refining: a case study of water footprint assessment in Jiangxi Province,China

Purpose

China is currently facing water scarcity due to its large national population and rapid economic development. Lead is a typical non-ferrous metal. The lead industry is one of the top 10 water-consuming industries in China and suffers from the heavy burden of properly managing discharged wastewater containing heavy metals and organic pollutants. Accordingly, a water footprint analysis of lead refining was conducted in this study to enhance the water management in China’s lead industry. This study is part 2 of the environmental improvement for lead-refining series.

Methods

In accordance with the ISO 14046 standard, life cycle assessment-based water footprint analysis was applied to a lead-refining enterprise in Jiangxi Province, China. Five midpoint (i.e., water scarcity, aquatic eutrophication, carcinogens, non-carcinogens, and freshwater ecotoxicity) and two endpoint (i.e., human health and ecosystem quality) indicators are utilized to assess the water footprint impact results.

Results and discussion

Direct pollutant emissions are a major contributor to ecosystem quality and freshwater ecotoxicity, whereas indirect processes (i.e., industrial hazardous waste landfill, transport, and chemicals) contribute considerably to human health, aquatic eutrophication, and carcinogen categories. Chromium, copper, arsenic, and zinc were the key substances in the lead production chain, and their emissions exerted a significant impact on human health and ecosystem quality.

Conclusions

Reducing direct copper emission was the most important key to minimizing ecosystem quality decline in China’s lead industry, and optimizing indirect processes was effective in mitigating the impact on human health. Enhancing wastewater treatment, increasing chemical consumption efficiency, optimizing transport and industrial hazardous waste disposal, improving supervision, issuing relevant governmental regulations, and adopting advanced wastewater treatment technologies are urgently needed to control the water footprint.

     

Evaluation of a Most-Probable-Number Technique for the Enumeration of Pseudomonas aeruginosa

A most-probable-number (MPN) technique was evaluated for detecting and enumerating Pseudomonas aeruginosa in water and wastewater. Both the presumptive and confirmatory media, as described in the 13th edition of Standard Methods for the Examination of Water and Wastewater, as well as modifications of these media were included in evaluations. Various samples of water were tested, namely chlorinated tap water, creek water, and influent to a wastewater treatment plant. Modified media repeatedly gave higher estimated MPNs of P. aeruginosa than media listed in Standard Methods. P. aeruginosa was detected and recovered from all creek water and wastewater samples, but not from tap water samples tested. This organism was determined to be present in as large numbers as the fecal coliforms and in even greater quantities than the fecal streptococci in all samples, whenever MPN estimations were determined from those positive tubes containing the modified confirmatory medium.     

WETLANDS AS ACCRETING SYSTEMS: WASTEWATER TREATMENT

SUMMARY

Considerable attention has been directed in the last decade to the use of wetlands for wastewater treatment. They are generally very effective in reducing (by up to 95%) the concentrations of nitrogen, pathogenic bacteria and heavy metals but their efficiencies in reducing phosphorus and organic matter vary widely. While most of the processes which result in removal of wastewater constituents are qualitatively understood, quantitative data are lacking. It is therefore impossible to predict the potential of any wetland for wastewater treatment or to manage wetlands for optimum treatment efficiency. Little is known of either short- or long-term effects of wastewater addition on wetland ecosystems.

In view of the substantial economic benefits of using wetlands for wastewater treatment, it is suggested that studies on wastewater treatment by both artificial and natural wetlands in South Africa are urgently required.     

Vegetable crop irrigation with tertiary filtered municipal wastewater

Abstract

The use of tertiary membrane-filtered municipal wastewater for irrigation as an alternative to natural freshwater sources was evaluated. Membrane filtration was considered as a viable technology to reclaim wastewater for irrigation, and the microbial and heavy metal impact on crops and soil was studied. The results of 2 years of research (2003 – 2004), carried out in Cerignola in the South of Italy, are reported. Tertiary treatment was carried out using a membrane filtration pilot plant with a hollow fibre submerged system. The water produced was used for drip irrigation of three vegetable crops in succession – processing tomato, fennel and lettuce – and compared with conventional water. Microbiological analyses were performed on the water used for irrigation, on soil samples and on marketable crops. Results show that the microbial content of soil and crops did not show relevant differences in relation to the two types of water. The measured values of heavy metals concentration in crops never exceeded toxic values. The filtered wastewater never caused an increase of bacterial concentration in the soil nor on the edible part of crops. Therefore, tertiary filtered municipal wastewater can be considered a valid alternative source of water for vegetable crop irrigation.     

Phytoremediation of Parboiled Rice Mill Wastewater Using Water Lettuce (Pistia Stratiotes)

Phytoremediation is an emerging technology applied for treatment of wastewater. It is a suitable option notably in developing countries as it is simple, sustainable and cost effective. In the present lab-based batch study the free floating aquatic plant water lettuce (Pistia stratiotes) is used for treatment of parboiled rice mill wastewater having low pH, high chemical oxygen demand (COD), nitrogen, and phosphate. In raw rice mill wastewater (undiluted) growth of water lettuce is found to be inhibited. Later on, two different dilution approaches (raw and facultative pond effluent 1:1; raw and tap water 1:1) are applied in order to effectively use this technology. In all cases a control (without plant) is maintained to compare the performance with the Aquatic Plant based Treatment (APT) system. In the APT system results reveal that removal of soluble COD (SCOD), ammoniacal nitrogen (NH₄-N), nitrate nitrogen (NO₃-N), and soluble phosphorus (sol. P) are upto 65%, 98%, 70%, and 65% respectively. The study highlights the efficacy of water lettuce in removing organics and nutrients from parboiled rice mill wastewater.     

To study the performance of biocarriers in moving bed biofilm reactor (MBBR) technology and kinetics of biofilm for retrofitting the existing aerobic treatment systems: a review

Moving bed biofilm reactor (MBBR) incorporates benefits provided by both attached and suspended growth systems. It is an advanced high rate wastewater treatment technology with high treatment efficiency; low capital, operational, maintenance and replacement cost; single reliable and robust operation procedure. Moreover, this technology is applicable to wide range of wastewater flows ranging from 10,000 to 150,000 m³ day^?1. The MBBR has proved to be effective in removing up to 90 % chemical oxygen demand and 95 % biochemical oxygen demand with nutrients from the effluent stream at optimum condition, provided there is sufficient retention time. It is a cost-effective way of upgrading existing wastewater treatment system as it is efficient, compact and easy to operate. This process can be provided for new sewage treatment works or for retrofitting existing wastewater treatment plants where a higher treated effluent standard is required without any running and capital cost. The performance of MBBR depends on the percent of media provided in the reactor, surface area of the biocarrier, dissolved oxygen and the organic loading. Various mathematical models are also described in this review paper which is generally used to calculate the reactor volume, effluent organic concentration and substrate removal rate.     

Energy requirements for nitrification and biological nitrogen removal in engineered wetlands

Nitrogen in wastewater degrades aquifer and surface water quality. To protect water quality in the United States, nitrogen discharge standards are strict: typically 1.0 mg/L NH₄-N for discharge to surface water and 10 mg/L total nitrogen (TN) for discharge to soil. Passive constructed wetland treatment systems cannot meet the nitrification standards discussed in this paper, using loading rates commonly considered to be cost-effective based on economic conditions in North America. Although partial nitrification can be achieved with some vertically or intermittently loaded, subsurface flow (SSF) wetlands, complete nitrification cannot be achieved in these passive wetland treatment systems. Engineered wetlands (EWs) use mechanical power inputs via pumping of air or water to nitrify wastewater, and have evolved in large part to nitrify wastewater. The design energy requirements for these power inputs have yet to be described in the wetland treatment literature. Our paper investigates the energy and area requirements of three wetland technologies: aerated subsurface flow, tidal flow, and pulse-fed wetland treatment, compared to a mechanical activated-sludge treatment system.     

Electricity generation from real industrial wastewater using a single-chamber air cathode microbial fuel cell with an activated carbon anode

This study introduces activated carbon (AC) as an effective anode for microbial fuel cells (MFCs) using real industrial wastewater without treatment or addition of external microorganism mediators. Inexpensive activated carbon is introduced as a proper electrode alternative to carbon cloth and carbon paper materials, which are considered too expensive for the large-scale application of MFCs. AC has a porous interconnected structure with a high bio-available surface area. The large surface area, in addition to the high macro porosity, facilitates the high performance by reducing electron transfer resistance. Extensive characterization, including surface morphology, material chemistry, surface area, mechanical strength and biofilm adhesion, was conducted to confirm the effectiveness of the AC material as an anode in MFCs. The electrochemical performance of AC was also compared to other anodes, i.e., Teflon-treated carbon cloth (CCT), Teflon-treated carbon paper (CPT), untreated carbon cloth (CC) and untreated carbon paper (CP). Initial tests of a single air-cathode MFC display a current density of 1792 mAm⁻², which is approximately four times greater than the maximum value of the other anode materials. COD analyses and Coulombic efficiency (CE) measurements for AC-MFC show the greatest removal of organic compounds and the highest CE efficiency (60 and 71%, respectively). Overall, this study shows a new economical technique for power generation from real industrial wastewater with no treatment and using inexpensive electrode materials.

     

Comparative life cycle sustainability assessment of urban water reuse at various centralization scales

Purpose

Population growth and urbanization lead to increasing water demand, putting significant pressure on natural water sources. The rising amounts of domestic wastewater (WW) in urban areas may be treated to serve as an alternative water source that may alleviate this pressure. This study examines sustainability of utilizing reclaimed domestic wastewater in urban households for toilet flushing and garden irrigation. It models a city characterized by water scarcity, using a coal-based electricity mix.

Methods

Four approaches were compared: (0) Business-as-usual (BAU) alternative, where the central WW treatment plant effluent is discharged to nature; (1) central WW treatment and urban reuse of the effluent produced; (2) semi-distributed greywater treatment and reuse, at cluster scale; (3) Distributed greywater treatment and reuse, at building scale. Environmental life cycle assessment (LCA), social LCA (S-LCA), and life cycle costing (LCC) were applied to the system model of the above scenarios, with seawater desalination as the source for potable water. System boundaries include water supply, WW collection, and treatment facilities. Analytical hierarchy process (AHP), a multi-criteria decision analysis (MCDA) methodology, was integrated into the life cycle sustainability assessment (LCSA) framework as a means for weighting sustainability criteria through judgment elicitation from a panel of 20 experts.

Results and discussion

Environmentally and socially, the two distributed alternatives perform better in most impact categories. Socially, semi-distributed (cluster scale) reuse is somewhat advantageous over the fully distributed alternative (building scale), due to the benefits of community engagement. Economically, the cluster-level scenario is the most preferable, while the building-scale scenario is the least preferable. A hierarchical representation of the problem’s criteria was constructed, according to the principals of AHP. Each criterion was weighted and those of extreme low importance were eliminated, while maintaining the integrity of the experts’ judgments. Weighted and aggregated sustainability scores revealed that cluster level reclamation, under modeled conditions, is the most sustainable option and the BAU scenario is the least sustainable. The other two alternatives, centralized and fully distributed reclamation, obtained similar intermediate scores.

Conclusions

Distributed urban water reuse was found to be more sustainable than current practice. Different alternative solutions are advantageous in different ways, but overall, the reclamation and reuse of greywater at the cluster level seems to be the best option among the three reuse options examined in this assessment. AHP proved an effective method for aggregating the multiple sustainability criteria. The hierarchical view maintains transparency of all local weights while leading to the final weight vector.

     

Moving forward in the use of aerobic granular sludge for municipal wastewater treatment: an overview

Activated sludge is one of the most widely implemented technologies for municipal wastewater treatment. Yet, more restrictive environmental standards demand for more efficient technologies. Aerobic granular sludge (AGS) is a promising alternative in this context since this technology has shown potential for simultaneous organic matter and nutrient removal using smaller bioreactors and consuming less energy. However, despite such engaging claims, only ca. 40 full-scale AGS systems have been installed worldwide after 30 years of development. This reduced implementation suggests the existence of significant bottlenecks for this technology, which currently only have partially been overcome. This overview aims to analyze the recent progress in R&D concerning aerobic sludge granulation for municipal wastewater treatment via the analysis of research articles and invention patents as well as to elucidate exiting technological gaps and development opportunities. Culturing methods aiming at fast granulation, long-term stability and excellent process performance are of utmost interest for promoting massive implementation of full-scale AGS systems. Moreover, the recovery of biomaterials from waste sludge could contribute to the implementation of the biorefinery paradigm in wastewater treatment plants.

     

Comparison of constructed reed beds with different filter media and macrophytes treating urban stream water contaminated with lead and copper

The aim of this study was to investigate the treatment efficiency of passive vertical-flow constructed wetland filters containing different macrophytes (Phragmites and/or Typha) and granular media with different adsorption capacities. Different concentrations of lead and copper sulphate were added to the polluted urban stream inflow water to simulate pre-treated mine wastewater. A fertilizer was added to one filter only. The relationships between growth media and plant communities as well as the reduction of predominantly lead and copper were investigated. Lead, copper and 5-day biochemical oxygen demand (BOD) concentrations were reduced similarly for all the wetlands. An analysis of variance showed that the concentration reductions (mg/l) of lead, copper and BOD were significantly similar for the six experimental wetlands. There appears to be no additional benefit in using expensive adsorption media like granular activated carbon to enhance biomass performance during the first 10 months of operation.     

Current research trends on microplastic pollution from wastewater systems: a critical review

Microplastics have been widely considered as contaminants for the environment and biota. Till now, most previous studies have focused on the identification and characterization of microplastics in freshwater, sea water, and the terrestrial environment. Although microplastics have been extensively detected in the wastewater, research in this area is still lacking and not thoroughly understood. To fill this knowledge gap, the current review article covers the analytical methods of microplastics originating from wastewater streams and describes their sources and occurrences in wastewater treatment plants (WWTPs). Studies indicated that microplastic pollution caused by domestic washing of synthetic fibers could be detected in the effluent; however, most microplastics from personal care and cosmetic products (PCCPs) can be efficiently removed during wastewater treatment. Moreover, various techniques for sampling and analyzing microplastics from wastewater systems are reviewed; while, the implementation of standardized protocols for microplastics is required. Finally, the fate of microplastics during wastewater treatments and the environmental contamination of effluent to environment are presented. Previous studies reported that the advanced wastewater treatment (e.g., membrane bioreactor) is needed for improving the removal efficiency of small-sized microplastics (<?100 µm). Although the role of microplastics as transport vectors for persistent organic pollutants (POPs) is still under debate, they have demonstrated abilities to absorb harmful agents like pharmaceuticals.