Alternatives to the use of synthetic organic coagulant aids in drinking water treatment: improvements in the application of the crude extract of Moringa oleifera seed

[EN] Drinking water treatment is a process based on multiple stages that has a main objective to provide water safe enough to be consumed by humans. Coagulation–flocculation is used to remove colloidal and suspended solids. This process improves the performance of subsequent stages (as sedimentation or filtration) as well as the water quality with a desired end-use. For many years, inorganic and organic synthetic polyelectrolytes have been used in coagulation–flocculation processes. However, its use has been deeply studied recently to determine the potential impact of residual concentration of these substances on human health and the environment. Strict regulations limit the concentration of free residual monomer after the addition of polyacrylamide (PAM) in drinking water treatment and study the effect of interaction of the residues with disinfection products. Therefore, in the last years there has been a resurgence of interest to use natural materials with the same performance that synthetic, but with lower hazard for the environment and humans. This work studies the use of the flocculant extracted from Moringa oleifera seed, in combination with polyaluminum chloride (PAC). The performance is compared with the combination PAC–PAM in terms of coagulant activity and physical–chemical quality of the water treated. Jar test was carried out using two types of natural water (with presence of bentonites) and different combinations of coagulant and flocculants. Results show that coagulant activity of PAC–Moringa combination is comparable with the results obtained with PAC–PAM, reducing initial turbidity up to 90% in all the tests. With regard to physical–chemical quality of the treated water, PAC–Moringa produces values under the drinking water quality standards for all the parameters analyzed. It is remarkable that the decrease of 50% in the trihalomethanes formation potential rate shown for PAC–Moringa combination, observed when treating natural water with presence of bentonites. Therefore, the results obtain in this work encourage the use of Moringa oleifera extract as a natural, low cost, effective, and low-toxicity alternative to the use of synthetic organic polyelectrolytes as polyacrylamide for drinking water treatment.This research has been done in the framework of the project “Study of synthetic and natural coagulants susceptible of being used in the water treatment plant of “Ribarroja del Turia” (Valencia) as substitutes for polyacrylamide”. The authors wish to thank the staff of the laboratory of the Department of Water Quality of the company “Aguas de Valencia” located in La Presa (Manises) for its collaboration in the water tests of this work.García Fayos, B.; Arnal Arnal, JM.; Monforte Monleon, L.; Sancho Fernández, MP. (2015). 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Malaria transmission after five years of vector control on Bioko Island, Equatorial Guinea.

BACKGROUND: Malaria is endemic with year-round transmission on Bioko Island. The Bioko Island Malaria Control Project (BIMCP) started in 2004 with the aim to reduce malaria transmission and to ultimately eliminate malaria. While the project has been successful in reducing overall malaria morbidity and mortality, foci of high malaria transmission still persist on the island. Results from the 2009 entomological collections are reported here. METHODS: Human landing collections (HLC) and light trap collections (LTC) were carried out on Bioko Island, Equatorial Guinea in 2009. The HLCs were performed in three locations every second month and LTCs were carried out in 10 locations every second week. Molecular analyses were performed to identify species, detect sporozoites, and identify potential insecticide resistance alleles. RESULTS: The entomological inoculation rates (EIR) on Bioko Island ranged from 163 to 840, with the outdoor EIRs reaching > 900 infective mosquito bites per year. All three human landing collection sites on Bioko Island had an annual EIR exceeding the calculated African average of 121 infective bites per year. The highest recorded EIRs were in Punta Europa in northwestern Bioko Island with human biting rates of 92 and 66 mosquito landings per person per night, outdoors and indoors, respectively. Overall, the propensity for mosquito biting on the island was significantly higher outdoors than indoors (p < 0.001). Both Anopheles gambiae s.s. and An. melas were responsible for malaria transmission on the island, but with different geographical distribution patterns. Sporozoite rates were the highest in An. gambiae s.s. populations ranging from 3.1% in Punta Europa and 5.7% in Riaba in the southeast. Only the L1014F (kdr-west) insecticide resistance mutation was detected on the island with frequencies ranging from 22-88% in An. gambiae s.s. No insecticide resistance alleles were detected in the An. melas populations. CONCLUSIONS: In spite of five years of extensive malaria control and a generalized reduction in the force of transmission, parasite prevalence and child mortality, foci of very high transmission persist on Bioko Island, particularly in the northwestern Punta Europa area. This area is favorable for anopheline mosquito breeding; human biting rates are high, and the EIRs are among the highest ever recorded. Both vector species collected in the study have a propensity to bite outdoors more frequently than indoors. Despite current vector control efforts mosquito densities remain high in such foci of high malaria transmission. To further reduce transmission, indoor residual spraying (IRS) needs to be supplemented with additional vector control interventions