Pretreatment using Opuntia cochenillifera followed by household slow sand filters: technological alternatives for supplying isolated communities

• Published in: Environmental technology Vol. 41; no. 21; pp. 2783 - 2794
• Main Authors: Souza Freitas, Bárbara Luíza, Sabogal-Paz, Lyda Patricia
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 18-09-2020; Taylor & Francis Ltd
• Subjects: biosand filters; Coagulants; coagulation; Continuous flow; decentralized treatment; E coli; Filters; Fragility; Influent water; isolated communities; Larvae; Opuntia cochenillifera; Pretreatment; proximate analysis; RDF; Safe water; Sand; Sand filters; thermogravimetry; Toxicity; Turbidity; ultimate analysis; waste to energy; Water purification
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2019.1582700

Household slow sand filter (HSSF) performance in continuous and intermittent flows was evaluated when influent water was treated with a natural coagulant extracted from Opuntia cochenillifera. The water under study, used as influent, had a turbidity of 111 ± 17.3 NTU. When clarifying the water with O. cochenillifera, the best condition obtained was 30  mg L
−1
in natural pH (without correction), generating clarified water with turbidity satisfactory to filters operation (7.83 ± 2.32 NTU). The results indicated a better performance of continuous flow HSSF in turbidity removal (79.2% ± 8.39%) and higher efficiency of intermittent flow HSSF in the removal of E. coli (2.86 log ± 0.79 log for 12  h pause period and 2.41 log ± 0.42 log for 4  h pause period). For the sake of comparison, the evaluated HSSFs had the same production (60 L day
−1
). The impact on the interruption of the 96-h feed into the HSSFs was analysed and the results indicated a significant change in the quality of the filtered water after resuming the operation. This fragility of technology must be considered when it is implemented as lack of water can be a reality in the target communities. Acute toxicological assays with C. xanthus larvae showed no toxicity for pretreated and filtered water; however, more testing should be performed.