Field Evaluation of Long-Term Performance and Use of Biosand Filters in Posoltega, Nicaragua

Abstract

An evaluation was conducted in 2007 on biosand filters that were installed in Posoltega, Nicaragua in 1999 and 2004.The objectives were to characterize the condition and use of filters eight and three years after installation, determine filter performance of those filters still in use, and identify determinants of successful long-term use and performance. Methods consisted of household identification, user questionnaires, and water quality testing. Of the 234 filters installed, only 24 were found to still be in use. Average log reductions were 1.73 (98%) for total coliforms, 1.36 (96%) for Escherichia Coli, and 0.91 (88%) for turbidity. Statistically significant effects were detected for the magnitude of the contamination of source water, the peak hydraulic loading rate, and the standing depth of water over the filter media. Questionnaire results indicated user training on filter maintenance could improve the peak hydraulic loading rate and hence filter performance. The low rate of sustained use (10%) is an indication of failed implementation, and is attributable to structural failure, particularly cracking of the concrete filters from 2004. Nonetheless, this evaluation demonstrated the biosand filter technology to be robust since those filters still in use were performing as expected three and eight years postimplementation.

Household Water Treatment Technologies For Microbial Removal in Kabale District, Southwestern Uganda

“…The study found out microbial removal effectiveness of biosand filter did not significantly differ between source water samples; KMS2, RWA1 and KMS1 ( Table 2). The present study partially supports Vanderzwaag et al (2009), who reported that average log reductions were 1.7 (98%) for total coliforms and 1.4 (96%) for Escherichia coli. Stauber et al (2011) reported that when analysis of biosand filters was restricted to samples that had higher Escherichia coli concentrations, removals greater than 99% were measured.…”

Household water treatment and safe storage – effectiveness and economics

“…Figures 9 and 10 provide a summary of the reported removal efficiencies of biosand filters. Overall, the reported log removals of biosand filters for bacteria (E. coli) and viruses (mostly echovirus and bacteriophage) are between 0-3 and 0-7, respectively (Ahammed and Davra, 2011;Akvopedia, 2014c;Baumgartner et al, 2007;Duke et al, 2006;Murphy et al, 2010a;Palmateer, 1999;Sswm.info, 2014;Stauber et al, 2009;Vanderzwaag et al, 2009;Wang et al, 2014). The log removal of bacteria is centred on 0.4-2; while the distribution of log removals reported for viruses is widely scattered.…”

Educational Concerns of Implementing Biosand Water Filters in Rural Uganda

“…One of their recommendations is, "Education about waterborne diseases, methods of safe water storage, and methods of disinfecting the stored filtered water should accompany the installation of the filter" (p. 9). Similarly, in a study of BSF use in Nicaragua, Vanderzwaag, Atwater and Bartlett (2009) found that improper operator use contributed decreased effectiveness of the filter:…”

“…The researchers found only 10% of the filters were still in use after 8 years. Of those still being used they averaged a reduction of 98% total coliforms (Vanderzwaag et al, 2009). The researchers suggested the low use rate was a result of a failure of implementation and specifically the cracking of the earlier concrete filters.…”

“…Earwaker (2006) found a use rate ranging from 44-100% depending on the village in rural Ethiopia after 4 years. The only study reviewed showing less use of BSFs after time was Vanderzwaag et al (2009) in Nicaragua where 10% were still in use; but this study assessed the BSFs after a longer period of time, 3-8 years. Also, the researchers noted an intervening hurricane that impacted households.…”