Assessment of the 20L SODIS bucket household water treatment technology under field conditions in rural Malawi.

Two billion people worldwide consume unsafe drinking water. The problem is particularly pronounced in Sub-Saharan Africa, where more than a quarter of the population relies on unimproved surface water sources. Based on the principles of solar water disinfection (SODIS), a new household water treatment technology, the SODIS bucket, was developed to improve the microbial quality of water from these sources based on controlled tests in a laboratory setting. This study set out to evaluate the efficacy of the technology in a field setting, in rural communities in the Chikwawa District in southern Malawi. SODIS experiments were carried out in two different vessels (1-L PET bottles and 20-L polypropylene SODIS buckets), over three months using unprotected water sources normally used by community members. Vessels were exposed to direct sunlight for 8 h per day in a village setting and were sampled at regular intervals to determine total coliforms, E. coli, turbidity, UV transmittance and UV dose. In these experiments, the SODIS bucket reached inactivation targets for E. coli (<1 CFU/100 mL) in two of seven experiments and for total coliforms in one of seven for total coliforms (<50 CFU/100 mL), despite having greater UV doses than were seen in the evaluation carried out under controlled conditions during the bucket's development. PET bottles reached inactivation targets for both E. coli and total coliforms in five of seven experiments. There was no single factor that could be identified as preventing adequate inactivation, but the role of organic matter, inconsistent nature of the water source, and vessel size, when coupled with organic matter, were identified as contributing factors. This study highlights the need for further prototyping to provide a suitable pre-treatment step for unprotected water sources, and the importance of field testing with real-life parameters to ensure new technologies are context appropriate.

Effect of operational strategies on microbial water quality in small scale intermittent water supply systems: The case of Moamba, Mozambique.

Intermittent drinking water supply affects the health of over 300 million people globally. In Mozambique, it is largely practiced in cities and small towns. This results in frequent microbial contamination of the supplied drinking water posing a health risk to consumers. In Moamba, a small town in Southern Mozambique with 2,500 water connections, the impact of changes in operational strategies, namely increased chlorine dosage, increased supply duration and first-flush, on the microbial water quality was studied to determine best practices. To that aim, water quality monitoring was enhanced to provide sufficient data on the microbial contamination from 452 samples under the different strategies. The water at the outlet of the water treatment plant during all strategies was free of E. coli complying to the national standards. However, E. coli could be detected at household level. By increasing the chlorine dosage, the number of samples that showed E. coli absence increased at the two sampling locations in the distribution network: in Cimento from 72% to 83% and in Matadouro from 52% to 86%. Modifying the number and duration of supply cycles showed a different impact on the water quality at both locations in the distribution network. A positive effect was shown in Cimento, where the mean concentrations decreased slightly from 0.54 to 0.23 CFU/100 mL and 16.7 to 7.3 CFU/100 mL for E. coli and total coliforms respectively. The percentage of samples positive for bacteria was, however, similar. In contrast, a negative effect was shown in Matadouro where the percentage of positive samples increased and the mean bacterial concentrations increased slightly: E. coli from 0.9 to 1.5 CFU/100 mL and total coliforms 17.6 to 23.0 CFU/100 mL. Enhanced water quality monitoring improved operational strategies safeguarding the microbial water quality. The E. coli contamination of the drinking water at household level could point at recontamination in the distribution or unsafe hygienic practices at household level. Presence of faecal contamination at household level indicates potential presence of pathogens posing a health risk to consumers. Increasing chlorine dosage ensured good microbiological drinking water quality but changing the number of supply cycles had no such effect.

Low voltage iron electrocoagulation as a tertiary treatment of municipal wastewater: removal of enteric pathogen indicators and antibiotic-resistant bacteria.

In this paper we analyse the feasibility of low voltage iron electrocoagulation as a means of municipal secondary effluent treatment with a focus on removal of microbial indicators, Antibiotic Resistant Bacteria (ARB) and nutrients. A laboratory scale batch unit equipped with iron electrodes was used on synthetic and real secondary effluent from a municipal wastewater treatment plant. Synthetic secondary effluent was separately assayed with spiked Escherichia coli WR1 and with bacteriophage ΦX174, while real effluent samples were screened before and after treatment for E. coli, Extended Spectrum Betalactamase-producing E. coli, Enterococci, Vancomycin Resistant Enterococci, Clostridium perfringens spores and somatic coliphages. Charge dosage (CD) and charge dosage rate (CDR) were used as the main process control parameters. Experiments with synthetic secondary effluent showed >4log10 and >5log10 removal for phage ΦX174 and for E. coli WR1, respectively. In real effluents, bacterial indicator removal exceeded 3.5log10, ARB were removed below detection limit (≥2.5log10), virus removal reached 2.3log10 and C. perfringens spore removal exceeded 2.5log10. Experiments in both real and synthetic wastewater showed that bacterial removal increased with increasing CD and decreasing CDR. Virus removal increased with increasing CD but was irresponsive to CDR. C. perfringens spore removal increased with increasing CD yet reached a removal plateau, being also irresponsive to CDR. Phosphate removal exceeded 99%, while total nitrogen and chemical oxygen demand removal were below 15% and 58%, respectively. Operational cost estimates were made for power and iron plate consumption, and were found to be in the range of 0.01 to 0.24€/m3 for the different assayed configurations. In conclusion, low voltage Fe-EC is a promising technology for pathogen reduction of secondary municipal effluents, with log10 removals comparable to those achieved by conventional disinfection methods such as chlorination, UV or ozonation.

Application of UVOX Redox® for swimming pool water treatment: Microbial inactivation, disinfection byproduct formation and micropollutant removal.

Alternative disinfection technologies may overcome some of the limitations of conventional treatment applied in swimming pools: chlorine-resistant pathogens (e.g. Cryptosporidium oocysts and Giardia cysts) and the formation of chlorinated disinfection byproducts. In this paper, results of full scale validation of an alternative disinfection technology UVOX Redox® (hereinafter referred to as UVOX) that combines ozonation and UV irradiation are presented. The performance was assessed in terms of microbial inactivation, disinfection byproduct formation and micropollutant removal. UVOX was able to achieve 1.4-2.7 log inactivation of Bacillus subtilis spores at water flows between 20 and 76 m³/h. Lower formation of trichloromethane and dichloroacetic acid was observed with UVOX followed by chlorination when compared to chlorination alone. However, due to the use of ozone and the presence of bromide in the pool water, the formation of trihalomethanes and haloacetic acids shifted to more brominated byproducts. Chlorine alone was able to remove the target micropollutants: acetaminophen, atenolol, caffeine, carbamazepine, estrone, estradiol, and venlafaxine (>97% removal) after 24 h, with the exception of ibuprofen (60% removal). The application of UVOX in chlorinated water enhanced the removal of ibuprofen. The application of UVOX could lower the usage of chlorine to the level that provides an adequate residual disinfection effect.