Potable Reuse Of Wastewater Research Articles

Wastewater reuse potential in Pakistan: guidelines for environment and public health protection

Pakistan is on the 'absolute water scarcity' list consisting of 17 countries which will not have enough water to maintain the present levels of per capita food production. Vital importance of water for sustaining life and promoting development, appropriate technological solutions to augment water resources. Raw wastewater is being used for agriculture irrigation purposes in Pakistan, which may provide an alternate water source however; it has adverse health and environmental impacts. Present status of wastewater generation and reuse are highlighted in the paper. Requirement of proper guidelines for the reuse of treated wastewater also addressed to mitigate the environmental pollution and public health problems in Pakistan.

Oxidation of dissolved organic matter in the effluent of a sewage treatment plant using ozone combined with hydrogen peroxide (O3/H2O2)

The effluent from the secondary clarifier of an Urban Sewage Treatment Plant was oxidized by the combined and simultaneous use of ozone and hydrogen peroxide. The purpose was to increase the wastewater's reuse potential by improving water quality. The removal of dissolved organic chemicals was enhanced by adding periodic pulses of hydrogen peroxide while keeping pH above 8.0 throughout the runs. These conditions led to almost complete mineralization in less than 1 h. Under similar conditions, without the addition of hydrogen peroxide, the removal of total organic carbon (TOC) was no higher than 35%. The evolution of TOC was related to the concentration of hydroxyl radicals using a second-order kinetic model in which the exposure to hydroxyl radical was included by assuming a quasi-steady-state approximation. The concentration of hydroxyl radical was computed using the experimental data from ozone and hydrogen peroxide. The kinetic constants for the hydroxyl-mediated mineralization process were determined for wastewaters collected during a 1-year sampling campaign. The results showed that the mineralization process takes place in two periods whose rate constants were linked to the chemical oxygen demand (COD) to biochemical oxygen demand (BOD) ratio and to the chloride content of wastewaters. During the first part of the runs, the specific rate of mineralization was high, before subsequently decreasing after a period of 5–15 min by an average factor of 6.4 whose 95% confidence interval was in the 3.4–9.3 range. The moles of TOC removed per mole of ozone consumed were in the range of 9.2–17.7 mg O3/mg TOC measured at maximum ozone efficiency, which always occurred within the first 10 min.

Religious, philosophical and environmentalist perspectives on potable wastewater reuse in Durban, South Africa

Durban is South Africa’s second most populous city and home adherents of many faiths, as well as a wide variety of political, cultural, religious, ethnic and environmental groups who might hold deep philosophical objections to wastewater reuse. It is also widely known that where wastewater recycling has been considered, public concerns have been intense, sometimes leading to the abandonment of initiatives. Project objectives were to determine if there are groups in Durban with — specifically — religious or philosophical objections to the potable reuse of wastewater. The goal was to gain knowledge of the presence of related “show stopping” objections likely to emerge out of Durban’s diverse communities should eThekwini Municipality (formerly City of Durban) embark upon a more comprehensive feasibility study of wastewater recycling to potable standards. This study was conducted in four stages: 1) literature review, (2) email survey to international experts, (3) local qualitative interviews, and (4) focus group discussion. The main findings of the study are: (a) No fundamental religious objections to potable wastewater reuse appear to exist either internationally or locally. (b) Concerns among local groups around the environment, global warming, water scarcity and pollution are present. (c) People are willing to think creatively about sustainability. (d) Key concerns, in Durban, are emotional (the “yuk” factor) and/or related to concerns about flagging technical competency. (e) Initiatives would be prone to politicization around equity/justice issues. In general, people are not comfortable with the idea of potable water recycling. People interviewed expressed that potable reuse was something they could consider with more information, understanding, and satisfactory quality assurance. By contrast, in a mixed focus group setting, a small and diverse group gravitated towards concerns that potable reuse shifted the burdens of inequitable and unjust water allocation patterns (residual from apartheid) to those who least benefited from the current system. Most people expressed a willingness to reject potable water reuse on the grounds that other interventions were possible that had better equity implications. This is echoed in the broader acceptability literature, which suggests that people feel that water reuse initiatives should start with big users and industry before households. Consensus converged around potable reuse as a last resort, indicating that potable reuse was “thinkable”, but not to maintain existing patterns of allocation and use.

Control of residual organic matter to reduce bacterial regrowth potential for wastewater reuse

Several problems have been reported about accumulated microorganisms in reclaimed water distribution systems. This paper presents the results of residual organic matter (OM) removal and apparent bacterial regrowth potential of treated wastewater obtained from laboratory-scale experiments using advanced biological treatments: two immobilization processes in series and a membrane bioreactor (MBR) process. Furthermore, a nanofiltration (NF) membrane process was applied to effluents of both advanced biological treatments. The immobilization process removed large molecular weight (MW) fractions >5,000 since immobilized microorganisms had sufficiently acclimated. The NF membrane was more effective in rejecting large MW fractions in the effluents of the immobilization and the MBR treatments. But it was difficult to reject small MW fractions <1,000 by NF. Neutral hydrophilic fraction of DOC was reduced by both advanced biological processes, and it can be thought that the microorganisms in the advanced processes could decompose and grow on some part of the neutral hydrophilic fraction. Quantity of attached microorganisms in the second immobilization reactor was significantly reduced compared to that in the first immobilization reactor. This suggests that apparent bacterial regrowth potential is controlled by the accumulation of effective microorganisms in the first reactor.

Analysis of wastewater reuse potential in Beijing

Increasing scarcity of freshwater resources and growing environmental awareness give rise to the use of reclaimed wastewater as an additional source of water supply. However, the amount of wastewater that can be reclaimed for reuse is subject to many factors, ranging from technical possibility to socio-economic and institutional conditions. Taking Beijing in China as a case study, this paper provides a systematic framework for the analysis of wastewater reuse potential under various driving forces and constraints. A linear programming model was used to analyse different reuse scenarios concerning alternative wastewater charges and reuse prices. The results suggest that the wastewater reuse potential is high at competitive prices. Wastewater treatment plants appear to be more economically efficient over on-site operation facilities in providing treated wastewater for reuse. The main users of the treated wastewater are agricultural irrigation and urban recreation sectors. The framework established in this study and the results of the Beijing case study help to better understand the complex systems and evaluate the effect of key factors influencing the potential of wastewater reuse. The study also provides a useful basis for the evaluation of wastewater reuse potential for other cities in China as well as cities in developing countries with similar conditions.

An assessment of the public health hazard potential of wastewater reuse for crop production. A case of Bulawayo city, Zimbabwe

Wastewater reuse is one possible way in which food production can be improved especially in developing countries where food is often scarce. However, the potential public health risks associated with wastewater use is of major concern. Health concerns are centered on pathogens and other health related pollutants that normally occur in the effluent. This research was conducted in Bulawayo, Zimbabwe during the period December 2005–May 2006. Bulawayo is a semi-arid area, with an average rainfall of 460 mm/annum and experiences frequent droughts. The study aimed at assessing the potential health impacts of effluent reuse for irrigating crops. Some 110 farmers are using wastewater for irrigation of vegetable crops on plots of about 500 m 2 each. Samples were collected from the effluent, the fields and vegetables and analyzed for selected quality parameters of health significance. Results were compared to national and international guidelines for effluent use in irrigation. Farmers’ knowledge on potential risks and practices were investigated through interviews. The results show that 70% of the respondents were aware of related health risks of using wastewater for irrigation. Respondents reported no major disease outbreaks. Mean values of pH were 8.1 and 7.3 for effluent and field soil and were within the FAO range of 6.5–8.5 for irrigation. Average temperature was 22.6 °C, while electrical conductivity ranged from 784 to 957 μS/cm and was less than the guideline value of 2000 μS/cm. Total coliforms in the effluent were found to be 7291 cfu/100 ml, while faecal coliforms were 5836 cfu/100 ml compared to the WHO limit of 1000 cfu/100 ml for irrigation. For effluent, cadmium were 0.04 mg/l and exceeded the long-term threshold limit of 0.01 mg/l, while lead was within the limit of 20 mg/l, with an average of 7.2 mg/l. No cadmium and lead were detected in the vegetables. It can be concluded that there is some health risks related to use of the effluent in the field, while for consumption of the vegetables there appears to be no risk. It is recommended that appropriate wastewater treatment mechanisms such as maturation ponds be put in place to reduce the coliform levels. Farmers must minimize direct contact with the effluent. The long-term impact of the irrigation on the soil for about 30 years and the seasonal impact to see variations on results need further studies.

Assessing the European wastewater reclamation and reuse potential — a scenario analysis

A model-based estimation of the wastewater reclamation and reuse potential in a European context is presented, and the effects of different water management scenarios on the appraisal are quantified. The impact of climate change on water availability and variation in the demand pattern and water use of considered countries is the modifying variable in these scenarios. The simulation demonstrates that there is a significant potential for an increased utilisation of reclaimed wastewater in many European countries, specifically in the Mediterranean region. Aspects related to the factors that will definitely drive or slow down the development are addressed.

Urban wastewater treatment plants and reuse potential in Turkey: selected examples from the western cities

The present study refers to the outcomes of a detailed survey on the current situation of Turkish Urban Wastewater Treatment Plants (UWWTPs). The survey covers the identification of the population served by UWWTPs, presentation of the current technologies (physical, biological and advanced) applied in the country's UWWTPs, prevailing effluent disposal criteria, detailed assessment of UWWTPs selected from the Western part of Turkey representing highly urbanised and industrialised districts, and elucidation of needs for upgrading the selected UWWTPs to comply with the current discharge standards and irrigation water quality criteria. Following an extensive data collection and evaluation step, Turkey's most recent situation in the number of UWWTPs, effluent produced in Turkish municipalities both quantity-and quality-wise, urban wastewater treatment types and disposal methods as well as reuse potential of treated urban wastewater have been presented and discussed.

Wastewater reclamation and reuse in Europe: a model-based potential estimation

The basic aim of this paper is to present an approach to quantitatively assess the potential of municipal wastewater reclamation and reuse in a European context. The model developed is based on the analysis and interrelation of water management data like water availability, water demand and treated effluent. In conjunction with information about the current status of wastewater reuse simple key figures are deduced, which allow future projection of wastewater reclamation and reuse. The simulation points out that there is a significant potential for an increased utilisation of reclaimed wastewater in many European countries, specifically in the Mediterranean region driven by different factors like increased wastewater treatment capacity and higher demand for irrigation and groundwater recharge.

Treatment and reuse of industrial effluents: case study of a thermal power plant

This paper presents a study of the potential of industrial wastewater reuse in Jordan's Al Hussein thermal power station. A comprehensive review of the processes involved, industrial waste generation and water requirements was carried out, and areas of potential improvment were identified. They include a water treatment system, blow-down system, flue gas desulfurization and finding alternative process water sources such as using sewage treatment plant effluent as make-up water. There is significant water pumped from the plant to the sewage plant and irrigation. Much of this wastewater could be treated by filtration, including reverse osmosis, and recirculated in the plant as process water. Water can very likely be conserved in the power plant by good operating practices such as preventative maintenance, good housekeeping, spill prevention, controlled storm run-off, cleaning techniques using minimum water, and a good training program to ensure program success. Since water conservation is very essential in Jordan, long-term plans should include consideration of changing the basic steam turbine technology to either the combined system or gas- and/or diesel-driven turbines at this power plant.

Water resources management in Crete (Greece) including water recycling and reuse and proposed quality criteria

In Crete, Greece despite having adequate atmospheric precipitation, water imbalance is often experienced, because of temporal and spatial variations in the precipitation, an increase in water demand during summer months and the difficulty of transporting water due to the mountainous terrain. Crete can be regarded as a representative mediterranean region with a relatively high potential for wastewater recycling and reuse. Preliminary estimates show that the implementation of wastewater recycling and reuse plans would lead to water savings of up to 5% of the total irrigation water. The basic aim of this paper is to present views on integrated water resources management in Crete, Greece including the potential for the recycling and reuse of treated wastewater. A preliminary inventory, distribution and mapping of wastewater treatment systems in Crete is also presented. Furthermore, the quality of treated effluents, disposal sites, irrigated areas, and environmental, social, economical, and agronomical impacts are considered. Finally, quality criteria for reuse of treated wastewater in Greece and maybe for other mediterranean countries are proposed.

Comparing microfiltration-reverse osmosis and soil-aquifer treatment for indirect potable reuse of water

Microfiltration (MF) followed by reverse osmosis (RO) and soil-aquifer treatment (SAT) are the two principal technologies considered for indirect potable reuse of wastewater. This study, conducted at the Northwest Water Reclamation Plant, Mesa (Arizona), evaluated MF/RO and SAT (>6 months residence time) treated tertiary effluent with respect to organics removal. Effluent organic matter was characterized as total organic carbon (TOC), by UV absorbance (UVA), solid-state carbon-13 nuclear magnetic resonance spectroscopy, and size exclusion chromatography. Several trace organic micropollutants, including EDTA, NTA, and alkylphenolethoxylate residues, were analyzed by GC/MS. The study revealed that final TOC concentrations of MF/RO and SAT are 0.3 and 1.0 mg l −1, respectively. Based on the characterization techniques used, the character of bulk organics present in final SAT water resembles the character of natural organic matter present in drinking water. Depending on the molecular weight cut-off, RO membranes can efficiently reject high molecular weight organic matter (characterized as humic and fulvic acids). However, approximately 40–50 percent of the remaining TOC in permeates consists of low molecular weight acids and neutrals representing a molecular weight range of ∼500 Da and less. In the SAT treated effluent, EDTA and APECs were removed to approximately 4.3 and 0.54 μg/l, respectively, but were below the detection limit in the MF/RO treated effluent.

Potential of industrial wastewater reuse

The potential of industrial wastewater reuse in Jordan is discussed. Industrial water requirements, wastewater production, types of pollutants in industrial wastewater and the technologies for wastewater treatment have been evaluated. A total of thirty industries have been reviewed. The total effluent from the thirty industries reviewed estimated at approximately 10,200 m 3/d. Of this amount, approximately 4,400 m 3/d are discharged to public sewerage system, which is about 3% of the total flow. The amounts of metals to be controlled are: 6800 kg/y, 3000 kg/y, 45 kg/y, 65 kg/y, 20 kg/y, 2 kg/y, 25 kg/y, 60 t/y and 8 t/y of Cr, Zn, Cu, Pb, Ni, Cd, Sn, Fe and Al, respectively. Nineteen industries, which discharge mainly organic polluted process wastewater, are food industries. Approximately 5.3 t of BOD/d is discharged from these industries. Of these, approximately 2.2 t BOD/d are discharged to the public sewerage system and about 3.1 t BOD are used for irrigation. It has been shown that most of the selected industries require some treatment of their wastewater. It is recommended to carry out further studies to establish the type of wastewater pretreatment strategies and their estimated capital cost. There is a need for the introduction of a cleaner technology in the selected industries. This could include substitution of raw and auxiliary materials, water and energy saving, recirculation of water, recovery of chemicals, improved process control, waste minimization, and good housekeeping.

In-plant control applications and their effect on treatability of a textile mill wastewater

Water minimization and exploration of the potential for wastewater recovery and reuse are priority issues of industrial wastewater management. They are extremely significant for the textile industry commonly characterized with a high water demand. The study presents a detailed in-plant control survey for a wool finishing plant. A comprehensive process profile and wastewater characterization indicate that process water consumption can be reduced by 34%, and 23% of the wastewater volume can be recovered for reuse. Treatability of reusable wastewater fraction and the effect of in-plant control applications on effluent treatability were also investigated.

Pathogen filtration, heterogeneity, and the potable reuse of wastewater.

Filtration is commonly employed in water and wastewater treatment to remove particles and reduce the concentration of microbial pathogens. All physical models of packed-bed filtration are based on a proportional relationship between particle removal per unit depth of bed and the local particle concentration, dC/dz = -C/l, where l is the filtration length scale. Although l is known to vary with time and filter depth for heterogeneous suspensions or "dirty" beds, this paper demonstrates that the filtration rates of even seemingly monodisperse particle suspensions under clean-bed filtration conditions cannot be described with a single filtration length scale. A new model is derived for particle filtration that accounts for heterogeneity at two different spatial scales. Heterogeneity at the scale of the pathogen and/or collector (microscale heterogeneity) leads to a slow power-law decay of contaminant concentration with distance, instead of the fast exponential decay predicted by the standard model. Heterogeneity at the filter scale (macroscale heterogeneity) provides another level of complexity that can be evaluated once microscale heterogeneity effects are characterized. This model for microscale and macroscale heterogeneous particle filtration is verified by filtration experiments on a recombinant analogue of the waterborne pathogen Norwalk virus.

How ‘Green’ Are Aquaculture, Constructed Wetlands and Conventional Wastewater Treatment Systems?

The term ‘green’ is nowadays widely used (and misused) in connection with many types of technologies. If a technology is ‘green’ it usually means that the technology requires less non-renewable energy sources than other alternatives. However, other parameters need to be considered as well, such as sustainability, recycling potential, treatment capacity and potential, conservation of ecosystems, etc. In this paper the energy requirements and nutrient recycling potential of constructed wetlands and wastewater aquaculture facilities are compared with that of conventional wastewater treatment technologies. The energy requirements of constructed wetlands are very low, but if significant reuse of nutrients is included (aquaculture), the energy requirements increase significantly and usually beyond the energy equivalent of the biomass produced. This is especially true in cold temperate climates where the aquaculture systems need to be housed in heated greenhouses and artificial light must be provided to secure operation throughout the year. In countries where fresh water itself is a limiting resource and where the economic capability may limit the use of artificial fertilisers, the reuse potential of wastewater may be more important. The potential for sustainable cropping of the plant biomass is excellent in tropical wetlands as the plants have a high productivity and a continuous growing season. In order to evaluate in more detail the ‘greenness’ of the different wastewater treatment technologies, the life-cycle approach might be applied. However, because constructed wetlands, besides the water quality improvement function, perform a multitude of other functions such as biodiversity, habitat, climatic, hydrological and public use functions, methodologies need to be developed to evaluate these functions and to weigh them in relation to the water quality issues.

Advanced Wastewater Disinfection Technologies: State of the Art and Perspectives

Chlorination/dechlorination and advanced disinfection processes (UV irradiation, ozonation, membrane filtration) have been reviewed in terms of their efficiency, regrowth potential, design parameters, experimental set-up, scale-up and industrial experiences. Existing results show the great influence of water quality, in particular of suspended matter concentration and organic content. The efficiency and reliability of these processes are evaluated for different reuse applications. The critical analysis of the literature data and experimental results highlights UV irradiation as an effective and competitive advanced disinfection process. Ozonation is a viable solution in case of higher requirements for water quality including virus and protozoa removal. Ultrafiltration is a highly efficient process producing an excellent quality and totally disinfected effluent, particularly recommended for groundwater recharge and potable wastewater reuse. The choice between these advanced disinfection technologies depends on wastewater quality, existing standards, specific reuse applications and wastewater treatment work capacity.

How ‘green’ are aquaculture, constructed wetlands and conventional wastewater treatment systems?

The term ‘green’ is nowadays widely used (and misused) in connection with many types of technologies. If a technology is ‘green’ it usually means that the technology requires less non-renewable energy sources than other alternatives. However, other parameters need to be considered as well, such as sustainability, recycling potential, treatment capacity and potential, conservation of ecosystems, etc. In this paper the energy requirements and nutrient recycling potential of constructed wetlands and wastewater aquaculture facilities are compared with that of conventional wastewater treatment technologies. The energy requirements of constructed wetlands are very low, but if significant reuse of nutrients is included (aquaculture), the energy requirements increase significantly and usually beyond the energy equivalent of the biomass produced. This is especially true in cold temperate climates where the aquaculture systems need to be housed in heated greenhouses and artificial light must be provided to secure operation throughout the year. In countries where fresh water itself is a limiting resource and where the economic capability may limit the use of artificial fertilisers, the reuse potential of wastewater may be more important. The potential for sustainable cropping of the plant biomass is excellent in tropical wetlands as the plants have a high productivity and a continuous growing season. In order to evaluate in more detail the ‘greenness’ of the different wastewater treatment technologies, the life-cycle approach might be applied. However, because constructed wetlands, besides the water quality improvement function, perform a multitude of other functions such as biodiversity, habitat, climatic, hydrological and public use functions, methodologies need to be developed to evaluate these functions and to weigh them in relation to the water quality issues.

Advanced wastewater disinfection technologies: State of the art and perspectives

Chlorination/dechlorination and advanced disinfection processes (UV irradiation, ozonation, membrane filtration) have been reviewed in terms of their efficiency, regrowth potential, design parameters, experimental set-up, scale-up and industrial experiences. Existing results show the great influence of water quality, in particular of suspended matter concentration and organic content.The efficiency and reliability of these processes are evaluated for different reuse applications. The critical analysis of the literature data and experimental results highlights UV irradiation as an effective and competitive advanced disinfection process. Ozonation is a viable solution in case of higher requirements for water quality including virus and protozoa removal. Ultrafiltration is a highly efficient process producing an excellent quality and totally disinfected effluent, particularly recommended for groundwater recharge and potable wastewater reuse. The choice between these advanced disinfection technologies depends on wastewater quality, existing standards, specific reuse applications and wastewater treatment work capacity.

Technologies for wastewater treatment appropriate for reuse: potential for applications in Greece

During the past 15 years, a wide variety of technologies have been developed that can be used for the treatment of wastewater for reuse applications. To assess the need for alternative technologies, potential reuse applications are reviewed. Changes in wastewater management, including the growing importance of decentralized wastewater management, is examined. The role of decentralized wastewater management is considered with respect to wastewater treatment, reclamation, and reuse. Technologies are presented and discussed for a wide range of reuse applications, ranging from individual homes to large centralized systems. The performance of representative technologies is assessed. A brief review of the water resources of Greece is presented to provide some perspective on the potential for wastewater reclamation and reuse in Greece.