Converting rain into drinking water: Quality issues and technological advances

With growing pressures on water supplies worldwide, rainwater harvesting is increasingly seen as a viable option to provide drinking water to an ever expanding population, particularly in developing countries. However, rooftop runoff is not without quality issues. Microbiological and chemical contamination have been detected in several studies, well above local and international guidelines, posing a health risk for consumers. Our research explores the use of silver ions, combined with conventional filtration and settling mechanisms, as a safe and affordable model for purification that can be applied on a small scale. The complete systems were installed and tested in rural communities in a Mexican semi-arid region. Efficiencies up to 99.9% were achieved in the removal of indicator microorganisms, with a marked exception where cross-contamination from external seepage occurs. Sites without overhanging branches or with relatively clean surfaces show an absence of total coliforms in the untreated runoff, compared with others where values as high as 1,650 CFU/100 ml were recorded. Thus, given adequate maintenance, the system can successfully deliver high quality drinking water, even when storage is required for long periods of time. © IWA Publishing 2011

Detection of trace peroxide explosives in environmental samples using solid phase extraction and liquid chromatography mass spectrometry

This paper presents solid phase extraction (SPE) and liquid chromatography-mass spectrometry (LC-MS) methods for the trace detection of the peroxide explosives triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD). Furthermore, experimental studies use these methods to explore the efficiency of wastewater treatment plant (WWTP) processes at removing trace levels of peroxide explosives from water samples to assess the application of the developed methods for the detection of explosives in the environment. The principal results of this study showed that the greatest removal of TATP and HMTD from spiked water samples occurred following the biological treatment stage, however, the WWTP processing did not completely remove all of the analytes from the water suggesting that such chemicals could contaminate downstream river water samples. The toxicity of chemical pollutants is often determined by their concentration, however, even at trace levels, the monitoring of explosives in the natural environment could be extremely informative for the detection of criminal activity as well as long term effects upon aquatic life. These findings also have significant implications for crime prevention and disruption approaches that can use this type of data as intelligence to guide investigations regarding the source and attribution of detected explosives

Application of pulsed UV-irradiation and pre-coagulation to control ultrafiltration membrane fouling in the treatment of micro-polluted surface water.

A major cause of ultrafiltration (UF) membrane fouling is the accumulation of microorganisms and their associated soluble products. To mitigate fouling the application of pulsed short-wavelength ultraviolet (UVC) light (around 254 nm) within the membrane tank together with pre-coagulation was investigated. In mini-pilot-scale tests carried out in parallel with conventional pre-treatment (CUF), the impact of pulsed UV (CUF-UV) at different UV irradiances and fluxes on the increase of trans-membrane pressure (TMP) was evaluated and explained in terms of the quantity and nature of membrane deposits in the membrane cake layer and pores. The results indicated that at a flux of 20 L m(-2) h(-1), the pulsed UV (1 min within 31 min cycle) at 3.17 × 10(-2) W/cm(2) prevented any measureable increase in TMP over a period of 32 days, while there was a fourfold increase in TMP for the conventional pre-treatment. For the CUF-UV system the concentration of bacteria and soluble microbial products was much less than the conventional CUF system, and the cake layer was thinner and contained less biopolymers (proteins and polysaccharides). In addition, the pores of the CUF-UV membrane appeared to have less organic deposits, and particularly fractions with a high molecular weight (>10 kDa). At a lower UV irradiance (1.08 × 10(-2) W/cm(2)), or higher flux (40 L m(-2) h(-1)) with the same UV irradiance, there was a measurable increase in TMP, indicating some fouling of the CUF-UV membrane, but the rate of TMP development was significantly lower (∼50%) than the conventional CUF membrane system. Overall, the results show the potential advantages of applying intermittent (pulsed) UVC irradiation with coagulation to control UF membrane fouling

Simultaneous measurement of free and conjugated estrogens in surface water using capillary liquid chromatography tandem mass spectrometry

Given detrimental impacts induced by estrogens at trace level, determination of them is significant but challenging due to their low content in environmental samples and inherent weak ionisation. A modified derivatisation-based methodology was applied for the first time to detect estrogen in free and conjugated forms including some isomers simultaneously using liquid chromatography tandem mass spectrometry (LC-MSn). Derivatisation reaction with previously used 1,2-dimethyl-1H-imidazole-5-sulphonyl chloride allowed significant increase of mass spectrometric signal of analytes and also provided distinctive fragmentation for their confirmation even in complicated matrix. Then satisfactory recovery (>75%) for the majority of analytes was achieved following optimisation of solid phase extraction (SPE) factors. The linearity was validated over a wide concentration with the correlation coefficient around 0.995. The repeatability of this methodology was also confirmed via the intra-day and inter-day precision and was less than 11.73%. Validation of method quantification limits (MQLs) for all chosen estrogens was conducted using 1000 mL surface water, ranging from 7.0 to 132.3 pg L−1. The established methodology was applied to profile presence of targeted estrogens in natural surface water samples. Out of the ten compounds of interest, three free estrogens (E1, E2, E3) and two sulphate estrogens (E1-3S and E2-3S) were found over their MQLs, being in the range of 0.05–0.32 ng L−1

The application of GAC sandwich slow sand filtration to remove pharmaceutical and personal care products

Lab-scale GAC sandwich slow sand filters with different GAC layer depths were evaluated for the first time to remove selected pharmaceutical and personal care products (PPCPs) (namely DEET, paracetamol, caffeine and triclosan, 25 μg/L). Coarse sand (effective grain size of 0.6 mm) was used instead of conventional fine sand. In addition to single sand and GAC filters, GAC sandwich filters were assessed at three filtration rates (i.e. 5 cm/h, 10 cm/h and 20 cm/h) to compare removals. Sandwich filter with 20 cm GAC achieved the best average PPCP removal (98.2%) at 10 cm/h rate. No significant difference of average PPCP removal was found between 10 and 20 cm/h filtration rates for the three GAC sandwich filters (p > 0.05). Among the selected PPCPs, DEET, the recalcitrant compound, was most effectively removed by the GAC sandwich filters. Combining the GAC layers with the slow sand filters significantly enhanced the removal of the target PPCP compounds (p  0.05). Results of this lab-scale investigation show that GAC sandwich slow sand filter is potentially an effective process for removing PPCPs from tertiary wastewater

A novel high-throughput analytical method to quantify microplastics in water by flow cytometry

Microplastics (MPs) are pervasive contaminants with unclear toxicological impacts. Current research on MP pollution relies on low-throughput methodologies, which are time-consuming and cannot directly measure MP concentration in suspensions. This study presents a qualitative and quantitative flow cytometry-based method for analysing MPs in water, offering a faster and more sustainable alternative. The method involves density separation to remove interfering particles, UV irradiation to eliminate microorganisms, and filtration to remove particles above 100 µm. The sensitivity of the method for different types of MPs, such as polystyrene (PS), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polyamide (PA) microbeads, ranges from 2 µg/L to 1 mg/L. For these MPs, good linearity was found in matrix-matched calibration where the most concentrated standard was 5 mg/L (R2 0.9820–0.9989) although the linear range can be larger (e.g. 42 mg MP/L for PS microbeads). The repeatability and reproducibility of the method for the model PS MP were <17.0% and 8.5%, respectively. The sample treatment method consisting of density separation and UV pretreatment, when carried out independently, led to 95.0% and 93.4% recoveries. The overall trueness of the optimized method for various sizes and compositions of microbeads is about 97%, according to validation supported by microscopy analysis. This method can substitute the traditional quantitative analytical approach based on counting microbeads with microscopy

Evaluation of a silver-ion based purification system for rainwater harvesting at a small-scale community level

Silver has been known for centuries to be a powerful disinfectant, with no known harmful effects to humans if applied in adequate doses. Although its use was partially discontinued with the advent of chlorination and modern antibiotics, the discovery of bacterial resistance and disinfection by-products has enabled its re-emergence as a viable water purification option. On the other hand, implementation in small-scale rainwater harvesting (RWH) systems has received little attention, possibly due to a general perception that it is a complex and/or expensive technology. This can be overcome by efficient designs that dose silver ions into the water at a minimal cost. The authors evaluated a dozen RWH systems equipped with silver releasing devices, which have been providing drinking water to schools and clinics in a rural area of Mexico. This paper represents a follow-up to a previously published study on an evaluation performed in the same region. A number of water quality parameters have been analysed, examining the long-term efficiency of the projects. Our observations show that the silver ion devices act as an effective disinfection mechanism, as long as adequate maintenance is provided. The combination with conventional settling tanks and filtration units seems to greatly enhance the overall performance of the system

Investigating reverse osmosis membrane fouling and scaling by membrane autopsy of a bench scale device

In response to the escalating world water demand and aiming to promote equal opportunities, reverse osmosis desalination has been widely implemented. Desalination is however constantly subjected to fouling and scaling which increase the cost of desalination by increasing the differential pressure of the membrane and through decline in permeate flux. A bench-scale desalination equipment has been used in this research to investigate the mitigation of fouling and scaling. This study also involved the performance of membrane autopsy for fouling characterisation with special attention to flux decline due to sulphate precipitation and biofouling. Visual inspection, scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and microbiology tests (API) were performed. Results obtained showed the presence of diatoms, pseudomonas and polysaccharides as the main foulants causing biofouling. Analysis revealed sulphate deposits as well as aluminium, calcium and silica as the main elements contributing to inorganic scaling. Findings pointed out that the pretreatment system of the small-scale reverse osmosis water treatment was inefficient and that selection of pretreatment chemicals should be based on its compatibility with the membrane structure. The importance of characterization for the verification of fouling mechanisms is emphasized

Assessing the Vulnerability of Agriculture Systems to Climate Change in Coastal Areas: A Novel Index

This study proposes a novel index to evaluate agricultural vulnerability to climate change in coastal areas, using the case of Andhra Pradesh, the state with the second longest coastline in India. Field data was collected from more than 1000 farmers (involved in over 50 varieties of crops) in 22 riverine and coastal case study areas. Data was collected through site visits, surveys and five workshops conducted between November 2018 and June 2019. Based on the collected data sets, a new Agricultural Coastal Vulnerability Index (AGCVI) was developed and applied to the 22 sites located in two districts (Krishna and Guntur) of Coastal Andhra Pradesh. The analysis revealed that the areas with three crop seasons (Kharif, Rabi and Zaid) per year are highly vulnerable to climate change. On the other hand, sites with one crop season (Kharif) per annum are the least vulnerable to climate change. Moreover, grains (particularly rice), flowers and fruit crops are more susceptible to climate change and its induced impacts. Rice is no longer a profitable crop in the case study areas partly as a result of unfavourable weather conditions, inadequate insurance provision and lack of government support for farmers. Cumulatively, all these circumstances impact farmers’ incomes and socio-cultural practices: this is leading to a marriage crisis, with a reduction in the desirability of matrimony to farmers. These findings provide valuable information that can support climate and agriculture policies, as well as sustainable cropping patterns among farmers’ communities in coastal areas of India in the future

Optimisation of biochar filter for handwashing wastewater treatment and potential treated water reuse for handwashing

Portable handwashing facilities help fight the transmission of water-borne diseases. However, in places lacking piped drainage systems, handwashing wastewater (HW) is commonly discarded into the ground. This harms the environment and public health and wastes reusable water. This study optimised the biochar filtration parameters such as particle size (0.5–2 mm), filter depth (15–30 cm) and flow rate (1–2.5 L/h) to remove colour, turbidity, phosphates and E. coli from HW using Response Surface Methodology. Fifteen configurations studied the impact of filtration parameters on pollutant removal. Quadratic models provided the best fit for pollution removal data. Optimal conditions were 1.25 mm particle size, 30 cm filter depth and 1 L/h flow rate, with predicted removals of 97.06, 97.50, 82.67 and 73.06 % for colour, turbidity, phosphates and E. coli, respectively. Biochar filter performance under optimal conditions validated the models. Actual removal efficiencies of 97.63, 99.85, 85.94 and 76.08 % for colour, turbidity, phosphates and E. coli, respectively, aligned closely with predicted values. Treated HW quality complied with several international water quality standards. Optimising biochar filtration is crucial for integrating this technology into portable handwashing facilities with potential water reuse, benefiting communities in developing countries with limited handwashing infrastructure and access to water