Tertiary-treated Wastewater Research Articles

Waterlogging in Arid Agriculture Areas Due to Improper Groundwater Management—An Example from Kuwait

Waterlogging is an acute problem in the agricultural areas of arid regions. This study highlights the main reasons for water table rise in the Wafra agriculture area of South Kuwait. A two-tier aquifer system exists in the area, which consists of the Kuwait Group aquifer underlain by a semi-confined Dammam aquifer. Improper sealing of wells tapping the semi-confined Dammam aquifer and over-irrigation were the main reasons for water level rise, and an increase in total dissolved solids was due to high evaporation of brackish water used for irrigation in the area. Other issues such as thin soil cover, topographic variation, and geomorphology within the area play an interactive role in the development of salt crusts on the ground surface. The key solution to the problem lies with proper well design and irrigation management. The sealing of the wells tapping the Dammam Formation has resulted in the lowering of the water level, which has allowed the reclamation of farms. For sustainable management of the Wafra agriculture area, it is observed that only the Kuwait Group aquifer should be utilized for irrigation, dewatering should be carried out in selective low-lying areas, and the adoption of best irrigation practices can be the only way for sustainable agriculture development in the area. The use of tertiary-treated wastewater, along with groundwater from the Kuwait Group (KG) aquifer, can be a solution to sustain agriculture. The crop water requirement should be considered for irrigation application while using best practices such as drip irrigation.

Agro-industrial wastewater reuse for irrigation of a vegetable crop succession under Mediterranean conditions

In many countries of the Mediterranean region, characterized by frequent drought periods, agricultural production often occurs under water deficiency or conditions that cause the depletion of the existing water resources. In these areas, the reuse of reclaimed wastewater for crop irrigation could contribute to mitigate/decrease water shortage, support the agriculture sector and protect groundwater resources. In 1.5-year field experiments in Southern Italy (Apulia Region), the effects of irrigation with treated agro-industrial wastewater on soil properties, crops yield and qualitative traits of crop products, including their microbiological safety, were assessed. Groundwater (GW), secondary treated wastewater (SW) and tertiary treated wastewater (TW) from an innovative “on-demand” UV disinfection system were used to irrigate tomato and broccoli, cultivated in succession. The three irrigation water sources and the corresponding irrigated soils, plants and crop products were analyzed for the main physico-chemical characteristics, quali-quantitative parameters and fecal indicators. SW and TW showed higher values of the main physico-chemical parameters than GW. SW irrigated soil resulted in a significant increase of NH4-N, Na+, SAR, EC (below the threshold value beyond which a soil is defined as saline) during the first tomato crop cycle, and of pH during the broccoli growing season. Irrigation with treated wastewater did not significantly affect the marketable yield nor the qualitative traits of tomato and broccoli crops, except for the Na+ and NO3− content (below the threshold levels defined by the European guidelines for vegetables). High levels of E. coli (above the Italian limit for reuse), Fecal coliforms and Fecal enterococci (up to 104 CFU 100ml−1) were observed in the SW and, when chlorination was not done, in the TW. Nevertheless, E. coli was not isolated from any sample of soil, plant and crop product, probably due to its rapid die-off. Moreover, low concentrations of Fecal coliforms and Total heterotrophic count were found in plant and crop product. The drip irrigation system used, which avoided the close contact between water and plant, may have contributed to this. Under the conditions applied in this study, the reuse of treated agro-industrial wastewater for irrigation can be considered an effective way to cope with agricultural water shortage in the Mediterranean area.

Laboratory Investigation of Mineralization of Refractory Nitrogen from Sewage Treatment Plants.

Laboratory studies were conducted and modeled to evaluate whether refractory organic nitrogen in tertiary-treated wastewater effluent could become bioavailable by conversion to mineral forms. Multiday incubations of effluent collected from the Branford and New Haven, Connecticut, waste water treatment plants (WWTP) revealed low but steady conversion of organic nitrogen to nitrate (NO3-). In Branford, the principal form of organic nitrogen was dissolved, and in New Haven it was particulate. Modeling suggested that in both the cases conversion to NO3- from organic forms occurred at several per cent per day, and appeared to happen via the intermediary NH4+. The results suggest that organic nitrogen may be an important source of bioavailable N, contributing to the problem of hypoxia in Long Island Sound and other estuaries.

Effects of nitrate addition on water column methylmercury in Occoquan Reservoir, Virginia, USA

Mercury bioaccumulation in aquatic biota poses a widespread threat to human and environmental health. Methylmercury (MeHg), the toxic form of mercury, tends to build up under anaerobic conditions in the profundal zones of lakes. In this study we performed a two-year assessment of spatial and temporal patterns of dissolved oxygen, nitrate, MeHg, manganese (Mn) and iron (Fe) in Occoquan Reservoir, a large run-of-the-river drinking water reservoir in Virginia, USA. A tributary to the reservoir receives input of nitrate-rich tertiary-treated wastewater that enhances the oxidant capacity of bottom water. Multiple lines of evidence supported the hypothesis that the presences of nitrate and/or oxygen in bottom water correlated with low MeHg in bottom water. Bottom water MeHg was significantly lower in a nitrate-rich tributary (annual mean of 0.05 ng/L in both 2012 and 2013) compared to a nitrate-poor tributary (annual mean of 0.58 ng/L in 2012 and 0.21 ng/L in 2013). The presence of nitrate and oxygen in bottom water corresponded with significantly lower bottom water MeHg at an upstream station in the main reservoir (0.05 versus 0.11 ng/L in 2013). In 2012 the reservoir exhibited a longitudinal gradient with nitrate and oxygen decreasing and MeHg and Mn increasing downstream. In both study years, there was a clear threshold of oxygen equivalent (3–5 mg/L), a metric that combines the oxidant capacity of nitrate and oxygen, above which MeHg (<0.05 ng/L), Mn (<0.3 mg/L) and Fe (<0.5 mg/L) were low. Results indicated that the addition of nitrate-rich tertiary-treated wastewater to the bottom of anaerobic reservoirs can reduce MeHg concentrations, and potentially decrease mercury bioaccumulation, while increasing the safe water yield for potable use.

Assessing the concentration of phthalate esters (PAEs) and bisphenol A (BPA) and the genotoxic potential of treated wastewater (final effluent) in Saudi Arabia

Plasticizers such as phthalate esters (PAEs) and bisphenol A (BPA) are highly persistent organic pollutants that tend to bio-accumulate in humans through the soil-plant-animal food chain. Some studies have reported the potential carcinogenic and teratogenic effects in addition to their estrogenic activities. Water resources are scarce in Saudi Arabia, and several wastewater treatment plants (WTPs) have been constructed for agricultural and industrial use. This study was designed to: (1) measure the concentrations of BPA and six PAEs, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), bis (2-ethylhexyl) phthalate (DEHP) and dioctyl phthalate (DOP), in secondary- and tertiary-treated wastewater collected from five WTPs in three Saudi cities for four to five weeks and (2) test their potential genotoxicity. Three genotoxicological parameters were used: % tail DNA (%T), tail moment (TM) and percentage micronuclei (%MN). Both DBP and DEHP were detected in all treated wastewater samples. DMP, DEP, BBP, DOP, and BPA were found in 83.3, 84.2, 79, 73.7 and 97.4% of the samples, respectively. The levels of DMP (p<0.001), DOP (p<0.001) and BPA (p=0.001) were higher in tertiary- treated wastewater than secondary-treated wastewater, perhaps due to the influence of the molecular weight and polarity of the chemicals. Both weekly sampling frequency and WTP locations significantly affected the variability in our data. Treated wastewater from Wadi Al-Araj was able to induce DNA damage (%T and TM) in human lymphoblastoid TK6 cells that was statistically higher than wastewater from all other WTPs and in untreated TK6 cells (negative control). %MN in samples from both Wadi Al-Araj and Manfouah did not differ statistically but was significantly higher than in the untreated TK6 cells. This study also showed that the samples of tertiary-treated wastewater had a higher genotoxicological potential to induce DNA damage than the samples of secondary-treated wastewater. BPA and some PAEs in the treated wastewater might have the potential to induce genetic damage, despite their low levels. Genotoxicity, however, may also have been due to the presence of other contaminants. Our preliminary findings should be of concern to Saudi agriculture because long-term irrigation with treated wastewater could lead to the accumulation of PAEs and BPA in the soil and ultimately reach the human and animal food chain. WTPs need to remove pollutants more efficiently. Until then, a cautious use of treated wastewater for irrigation is recommended to avoid serious health impacts on local populations.

Faecal pollution on vegetables and soil drip irrigated with treated municipal wastewaters

A three-year study was carried out to evaluate the effects of three different types of municipal treated wastewater distributed by drip irrigation on the microbial quality of some vegetable crops. The three different treated wastewater were: a secondary effluent originated from the municipal treatment plant after screening and grit removal, primary clarifiers followed by activated sludge process and partial aerobic stabilization of the sludge, finally the chemical precipitation of phosphorus, denitrification and chlorination; the second source, a tertiary-treated wastewater is originated after that the secondary effluent is first treated through granular media sand filtration and then it is pumped into the second phase of treatment represented by ultra-filtration module equipped with hollow fibre membranes (nominal porosity 0.2μm). The third water source was a simplified lagooning treatment in which part of the secondary effluent is pumped outside of the municipal plant and it is collected in a big reversed pyramid-shaped land pit, in this tank the water resided for a 4–5 days before being distributed to crops. In an experimental field in southern Italy (Apulia region) the physico-chemical and microbiological characteristics of the irrigation waters and faecal pollution on typical vegetable crops of southern Italy environment were determined. Total and Faecal Coliforms, Escherichia coli, Salmonella and protozoa Giardia and Cryptosporidium were monitored in the irrigation water, on plants and on soil at harvesting time. The different quality of irrigation water affected yields. For microbial results, however, in spite of the water contained high levels of microbial load (248, 1713 and 123429 E. coli cfu 100mL−1 in Tertiary filtered Wastewater, Lagoon treated Wastewater and Secondary treated Wastewater, respectively), exceeding the values of law (10 E. coli cfu 100mL−1), on crops and on soil, at harvesting time revealed no pollution. Salmonella and Cryptosporidium were never found in water, soil and crops. These data show that it is possible to irrigate with municipal treated wastewater and how despite they have higher values than those imposed by Italian law, crops quality and soil do not present any problems of faecal pollution and therefore do not cause risks for human health.

Comparable levels of microbial contamination in soil and on tomato crops after drip irrigation with treated wastewater or potable water

To evaluate the impact of treated wastewater (TWW) irrigation for produce safety, field experiments were conducted to compare secondary and tertiary TWW with potable water using tomatoes as a model crop. Human pathogens including a suite of obligate and opportunistic bacterial pathogens (Campylobacter, Pseudomonas, Salmonella, Shigella, Staphylococcus), protozoa (Cryptosporidium and Giardia), and viruses (Adenovirus and Enterovirus) were monitored in two field trials using a combination of microscopic, cultivation-based, and molecular (qPCR) techniques. Results indicate that microbial contamination on the surface of tomatoes was not associated with the source of irrigation waters; fecal indicator bacteria (FIB) contamination was not statistically different on tomatoes irrigated with TWW or potable water. In fact, indicator bacteria testing did not predict the presence of pathogens in any of the matrices tested. Indicator bacteria and the opportunistic pathogens were detected in water, soil and on tomato surfaces from all irrigation treatment schemes, and were positively correlated with duration of time in the field (p<0.0001). Pathogen contamination (Cryptosporidium) was detected in secondary TWW (3/14 samples) and on the surface of a TWW irrigated tomato (1/41 samples). Furthermore, the Enterobacteriaceae species in the TWW were markedly different from those found in soil and tomato. The results indicate that (surface drip) irrigation with TWW did not result in the transfer of fecal indicator bacteria or microbial pathogens to the irrigated soil or crop. Moreover, parallel testing for pathogens with traditional culture-based and quantitative PCR indicates that specific and rapid molecular testing of pathogens appears to be a more appropriate strategy than fecal indicator testing for the determination of reclaimed water safety.

Evaluation of sustainable electron donors for nitrate removal in different water media

An external electron donor is usually included in wastewater and groundwater treatment systems to enhance nitrate removal through denitrification. The choice of electron donor is critical for both satisfactory denitrification rates and sustainable long-term performance. Electron donors that are waste products are preferred to pure organic chemicals. Different electron donors have been used to treat different water types and little is known as to whether there are any electron donors that are suitable for multiple applications. Seven different carbon rich waste products, including liquid and solid electron donors, were studied in comparison to pure acetate. Batch-scale tests were used to measure their ability to reduce nitrate concentrations in a pure nutrient solution, light greywater, secondary-treated wastewater and tertiary-treated wastewater. The tested electron donors removed oxidised nitrogen (NOx) at varying rates, ranging from 48 mg N/L/d (acetate) to 0.3 mg N/L/d (hardwood). The concentrations of transient nitrite accumulation also varied across the electron donors. The different water types had an influence on NOx removal rates, the extent of which was dependent on the type of electron donor. Overall, the highest rates were recorded in light greywater, followed by the pure nutrient solution and the two partially treated wastewaters. Cotton wool and rice hulls were found to be promising electron donors with good NOx removal rates, lower leachable nutrients and had the least variation in performance across water types.

Effects of reclaimed wastewater irrigation on olive (Olea europaea L. cv. ‘Koroneiki’) trees

Irrigation of olive trees with treated wastewaters in arid and semi-arid regions is becoming a necessary alternative to addressing issues of water shortages. The irrigation requires a careful monitoring of soil and plants for a range of parameters including salts, nutrients, micro-elements, heavy metals, toxic pollutants, and pathogens. A 3-years monitoring of the above parameters in soil and leaves of olive trees in Crete, Greece was conducted using trees that were irrigated with three types of water: secondary treated wastewater (STW), tertiary treated wastewater (TTW), and tap water (TW). Plant growth was similar for all irrigation sources as indicated by measured trunk diameter, plant height, and photosynthetic activity. In addition, no significant differences in mineral leaf content were observed. Accumulation of nutrients (mainly P and K) and salts (Na) in soils 2 years after the application of both types of treated wastewater were observed in comparison to tap water. Magnesium, calcium, and boron concentrations in treated wastewaters were higher than TW. However no effects on soil concentrations were reported. Concentration of polycyclic aromatic hydrocarbons in soil ranged from 349.0μgkg−1 to 395.4μgkg−1 values not significantly different between the examined water sources. Finally, E. coli mean content in STW was 3580±800MPN 100mL−1; however, the absence of microbial contamination was detected in leaves and fruits of olive trees. The results of this study suggest that STW and TTW can be applied successfully for the safe irrigation of the olive groves.

Reuse of refinery's tertiary-treated wastewater in cooling towers: microbiological monitoring.

The study was planned to quantify the distribution of bacteria between bulk water and biofilm formed on different materials in an industrial scale cooling tower system of an oil refinery operating with clarified and chlorinated freshwater (CCW) or chlorinated tertiary effluent (TRW) as makeup water. The sessile and planktonic heterotrophic bacteria and Pseudomonas aeruginosa densities were significantly higher in the cooling tower supplied with clarified and chlorinated freshwater (CTCW) (p < 0.05). In the two towers, the biofilm density was higher on the surface of glass slides and stainless steel coupons than on the surface of carbon steel coupons. The average corrosion rates of carbon steel coupons (0.4-0.8 millimeters per year (mpy)) and densities of sessile (12-1.47 × 10(3) colony-forming unit (CFU) cm(-1)) and planktonic (0-2.36 × 10(3) CFU mL(-1)) microbiota remained below of the maximum values of reference used by water treatment companies as indicative of efficient microbial control. These data indicate that the strategies of the water treatment station (WTS) (free chlorine) and industrial wastewater treatment station (IWTS) followed by reverse electrodialysis system (RES) (free chlorine plus chloramine) were effective for the microbiological control of the two makeup water sources.

The use of treated wastewater and fertigation in greenhouse pepper crop as affecting growth and fruit quality

The performance and suitability of tertiary treated wastewater (TW) and/or fertigation (F) in pepper plants were studied over a 4-month period in greenhouse conditions. Four treatments were used consisting of (1) water, (2) water + F, (3) TW, and (4) TW + F. The F and/or TW application increased plant height and plant biomass compared with the control plants (irrigated with water) while no differences were observed in the number of leaves produced. Plants grown with TW + F were thicker than control plants. The addition of F increased fruit number in both water and TW, which resulted in increased plant yield and fruit marketability for the water application but decreased mean fruit weight for TW application. The application of TW increased fruit total soluble solids but decreased fruit firmness whereas adding F, these changes were normalized. The F and/or TW application reduced fruit total phenolics, fruit acidity, and fruit length but not fruit diameter. No differences were observed in fruit dry matter content, fruit color/lightness (a, b, and L value). Bacteria (total coliform and Escherichia coli) units on the fruits did not differ among the treatments. The results indicate that wastewater may act as an alternative means of irrigation if following strict safety aspects while the fertigation acted beneficially.

Biofouling of reverse-osmosis membranes during tertiary wastewater desalination: Microbial community composition

Reverse-osmosis (RO) desalination is frequently used for the production of high-quality water from tertiary treated wastewater (TTWW). However, the RO desalination process is often hampered by biofouling, including membrane conditioning, microbial adhesion, and biofilm growth. The vast majority of biofilm exploration concentrated on the role of bacteria in biofouling neglecting additional microbial contributors, i.e., fungi and archaea. To better understand the RO biofouling process, bacterial, archaeal and fungal diversity was characterized in a laboratory-scale RO desalination plant exploring the TTWW (RO feed), the RO membrane and the RO feed tube biofilms. We sequenced 77,400 fragments of the ribosome small subunit-encoding gene (16S and 18S rRNA) to identify the microbial community members in these matrices. Our results suggest that the bacterial, archaeal but not fungal community significantly differ from the RO membrane biofouling layer to the feedwater and tube biofilm (P < 0.01). Moreover, the RO membrane supported a more diverse community compared to the communities monitored in the feedwater and the biofilm attached to the RO feedwater tube. The tube biofilm was dominated by Actinobacteria (91.2 ± 4.6%), while the Proteobacteria phylum dominated the feedwater and RO membrane (at relative abundance of 92.3 ± 4.4% and 71.5 ± 8.3%, respectively), albeit comprising different members. The archaea communities were dominated by Crenarchaeota (53.0 ± 6.9%, 32.5 ± 7.2% and 69%, respectively) and Euryarchaeota (43.3 ± 6.3%, 23.2 ± 4.8% and 24%, respectively) in all three matrices, though the communities' composition differed. But the fungal communities composition was similar in all matrices, dominated by Ascomycota (97.6 ± 2.7%). Our results suggest that the RO membrane is a selective surface, supporting unique bacterial, and to a lesser extent archaeal communities, yet it does not select for a fungal community.

Managed aquifer recharge using quaternary-treated wastewater: an economic perspective

An excess of 31 million m3/y of tertiary-treated wastewater is expected in Muscat, Oman, by 2015. This paper addresses the technical and cost estimation of managed aquifer recharge after reverse-osmosis treatment. The results indicate that the project is appealing from an economic perspective. The total cost varies between USD 0.353 and USD 0.550 per cubic metre, depending on the cost of electricity, the interest rate and the life span of the project. The project may face rejection from domestic users, who may be unwilling to accept mixing treated wastewater with the current water supply due to health risks. An alternative to indirect potable reuse is the installation of a separate network to service industrial users.

Formation potential of N-nitrosamines during the disinfection of treated wastewaters with sodium hypochlorite

This study investigated the formation of eight N-nitrosamines (N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-propylamine (NDPA), N-nitrosomorpholine (NMOR), 1-nitrosopyrrolidine (NPYR), 1-nitrosopiperidine (NPIP), and N-nitrosodibutylamine (NDBA)) after the chlorination (with NaOCl) of wastewater effluents from two wastewater treatment plants (WWTPs) located in North East Spain. Two different WWTPs, one with nitrification-denitrification process (CB1) and the other without (CB2) have been chosen. The concentrations of individual N-nitrosamines in non-chlorinated tertiary treated wastewater effluents ranged from <LOD to 75 ng L−1. That range increases to 114 and 1092 ng L−1 after chlorinating tertiary-treated wastewater samples at 5 and 15 mg L−1 of free chlorine, respectively. NDEA and NMEA are the most abundant compounds in both non-chlorinated and chlorinated secondary and tertiary-treated wastewater effluents. The disinfection of tertiary treated wastewater at 5 mg L−1 of free chlorine gave a total N-nitrosamines concentration of about 300 ng L−1 in samples from the two studied WWTPs. Total N-nitrosamine concentrations in chlorinated secondary treated wastewater samples were significantly higher than those obtained from the chlorination of tertiary treated wastewaters (p < 0.05). This may be due to the capacity of the tertiary treatment processes for removing N-nitrosamines precursors. The experiments have revealed that in addition to NDMA, relatively high concentrations of other N-nitrosamines are produced when treated wastewater effluents are disinfected with chlorine for agricultural irrigation purposes.

Comprehensive Evaluation of Biological Growth Control by Chlorine-Based Biocides in Power Plant Cooling Systems Using Tertiary Effluent

Recent studies have shown that treated municipal wastewater can be a reliable cooling water alternative to fresh water. However, elevated nutrient concentration and microbial population in wastewater lead to aggressive biological proliferation in the cooling system. Three chlorine-based biocides were evaluated for the control of biological growth in cooling systems using tertiary treated wastewater as makeup, based on their biocidal efficiency and cost-effectiveness. Optimal chemical regimens for achieving successful biological growth control were elucidated based on batch-, bench-, and pilot-scale experiments. Biocide usage and biological activity in planktonic and sessile phases were carefully monitored to understand biological growth potential and biocidal efficiency of the three disinfectants in this particular environment. Water parameters, such as temperature, cycles of concentration, and ammonia concentration in recirculating water, critically affected the biocide performance in recirculating cooling systems. Bench-scale recirculating tests were shown to adequately predict the biocide residual required for a pilot-scale cooling system. Optimal residuals needed for proper biological growth control were 1, 2-3, and 0.5-1 mg/L as Cl2 for NaOCl, preformed NH2Cl, and ClO2, respectively. Pilot-scale tests also revealed that Legionella pneumophila was absent from these cooling systems when using the disinfectants evaluated in this study. Cost analysis showed that NaOCl is the most cost-effective for controlling biological growth in power plant recirculating cooling systems using tertiary-treated wastewater as makeup.

Water quality and brine shrimp ( Artemia sp.) population in Al Wathba Lake, Al Wathba Wetland Reserve, Abu Dhabi Emirate, UAE

Al Wathba Lake is located at Al Wathba Wetland Reserve which is located 40 km east of Abu Dhabi Island on the left side of the truck road to Al Ain. The water body extends for approximately 1.5 km in length and 0.5 km in width with a maximum depth of almost two meters (in the period of 2010). Al Wathba Reserve exists primarily because it is supplied with tertiary treated waste water from the Mafraq Waste Water Treatment Plant (WWT). The salinity of the water throughout the lake is variable due to the fresh water input and the underlying Sabkha substrate. The maximum salinity recorded in the lake is 230 ppt although typically the salinity is around 180 ppt. Over the period of February 2010 to December 2010, monitoring programme was carried out with the purpose of understanding the population dynamics, ecology and habitat requirements of the brine shrimp (Artemia sp.) at Al Wathba Lake which is the main food source for greater flamingo (Phoenicopterus roseus) in the reserve. Nine fixed sampling locations, distributed all over the entire lake’s area and two inlet samples were sampled monthly at day time to determine water temperature, salinity, pH, dissolved oxygen, nitrite, nitrate, ammonia, phosphate, total organic carbon (TOC), copper, cadmium and iron. The monthly average of total number of Artemia numbers counted in the sample was between 1.3 and 115 individuals/L but varied significantly between months. For the period considered, cysts were noted to be more abundant than the adults. Key words: Water quality, brine shrimp, population, Al Wathba wetland reserve, physical parameters, chemical parameters.

Investigation on the Factors Affecting Corrosion of Tertiary-Treated Municipal Wastewater

Tertiary treatment of municipal wastewater is necessary to reduce its scaling potential for using as makeup water of circulating cooling systems. In this study the corrosivity and the factors affecting corrosion of municipal wastewater tertiary-treated by nanofiltration membrane process were assessed by weight-loss method. The results show that concentration of salt ions such as Ca2+, Mg2+, Cl- and SO42- has a significant effect on corrosivity to carbon steel. Certain quantity of calcium and magnesium ions could inhibit the corrosion of carbon steel, however, chlorine and sulfate ions could accelerate the corrosion of carbon steel. The corrosion inhibition effect of three inhibitors (PC-604, RP-101 and poly epoxy succinate (PESA)) in tertiary-treated municipal wastewater on the carbon steel was evaluated. PC-604 had the best corrosion inhibitor effect and the lowest dosage. This research has guiding significance for using tertiary-treated municipal wastewater as makeup water of circulating cooling systems.

Wastewater filtration and re-use: An alternative water source for London

The rapid growth and climate of the Greater London region have contributed towards large deficits in water supply. Inexpensive, energy-efficient and sustainable water resource schemes are increasingly sought as a means to boost supply. Here, we propose a small-scale recycling scheme whereby tertiary-treated wastewater is pumped to the Cretaceous chalk of the London Basin. By taking advantage of the natural filtration properties of the underlying chalk, contaminants can be effectively attenuated over relatively short length scales to result in pure water. The problem is approached from four different scales. First, we define two localities in London where such a pumping scheme might operate; regions which combine a thick unsaturated zone and high chalk transmissivity, both essential to ensure maximum contaminant removal and minimum environmental impact. Secondly, the effects of pumping fluid into the Chalk at the two localities are quantified using a finite-difference groundwater flow model. We show that rivers impose a regular groundwater flow regime, whereas pre-existing abstraction wells will lead to less predictable results. Thirdly, we consider the effect of fractures on channelling rapid fluid flow within the rock mass. By digitising a fracture map based upon outcrop measurements from chalk exposed on the Kent coast similar to that beneath London, we quantify transport patterns of wastewater after injection. Imbibition to the chalk matrix (and therefore filtration) will occur where fluid pressure gradients are highest, for instance around disconnected fracture tips. Finally we demonstrate the efficacy of chalk in contaminant removal by injecting an analogue ‘effluent’ through a chalk core. ICP-AES analysis on the recovered solution shows the contaminants (viz. a suite of heavy metals) are arrested or removed over relatively small time- and length-scales. Numerical and analytical solutions fit the data poorly, shedding some light on the importance of hydrodynamic dispersion of aqueous contaminants within the chalk.

Monitoring the occurrence of emerging contaminants in treated wastewater and groundwater between 2008 and 2010. The Baix Llobregat (Barcelona, Spain)

The occurrence of 166 emerging compounds and four heavy metals (Cd, Ni, Hg and Pb) in treated wastewater and groundwater has been monitored at the Llobregat delta (Barcelona, Spain) over a period of 3 years. Selected compounds were pharmaceuticals, personal care products (PCPs), dioxins, polycyclic aromatic hydrocarbons (PAHs) and priority substances included in the 2008/105/CE Directive. Analysis was performed in tertiary treated wastewater (TWW), after an additional treatment of ultrafiltration reverse osmosis and UV disinfection, and groundwater from a deep confined aquifer. This aquifer is artificially recharged with TWW through injection wells. After the advanced treatment, 38 pharmaceuticals, 9 PCPs, 9 pesticides and 7 PAHs still showed a frequency of detection higher than 25% in the TWW, although at low concentration levels (ng/l). Not all active compounds found in the TWW were present in groundwater, indicating possible degradation within the aquifer media after the injection. A number of chemicals, mainly 10 pesticides and 10 pharmaceuticals were only present in groundwater samples, confirming a different origin than the injected TWW, probably agricultural activities and/or infiltration of poorly treated wastewater.

Transformation of 1H-Benzotriazole by Ozone in Aqueous Solution

Recent studies have shown that 1H-benzotriazole is a widespread contaminant of wastewater and surface water. Although disinfection by ozone has been shown to efficiently remove this compound, the transformation products have not been identified. To that end, the reaction of ozone with 1H-benzotriazole in aqueous solution has been studied in real time employing quadrupole time-of-flight mass spectrometry (Q-TOF MS) and negative electrospray ionization. The transformation products have been identified by calculating their empirical formulas using accurate mass measurements, and further confirmed by performing the reaction with stable isotope-labeled 1H-benzotriazole and measuring product ion spectra. Stable reaction products were distinguished from transient species by plotting their extracted mass profiles. The products that resulted from ozone and hydroxyl radicals in the reaction were qualitatively identified by modifying the conditions to either promote the formation of hydroxyl radicals, or to scavenge them. Based on experimental evidence, a mechanism for the direct reaction between ozone and 1H-benzotriazole is proposed that results in the formation of 1H-1,2,3-triazole-4,5-dicarbaldehyde, which has an empirical formula of C(4)H(3)O(2)N(3). Lastly, it was confirmed that the same transformation products formed in surface water and tertiary-treated wastewater, although they were observed to degrade at higher ozone doses.