Association between the concentration of protozoa and surrogates in effluents of the slow sand filtration for water treatment

Abstract

Currently, a major challenge on producing high-quality drinking water is to monitor pathogens, such as Giardia, Cryptosporidium and enteric viruses. Due to limitations of the analytical methods available to detect pathogens in water, the research of surrogate indicators is an up-to-date subject. In view of these aspects, a pilot scale study was performed to evaluate the association between microbiological and physical indicators and the presence of Giardia spp and Cryptosporidium sp in the effluent of upflow and downflow slow sand filters. The results showed that efficient bacterial removal could indicate suitable protozoa removal. Although coliforms and Escherichia coli do not present the appropriate physiological profile for an "ideal" indicator, they are still good references for drinking water microbiological quality, specifically for slow sand filtration. The results also point out to the need of deeper researches about the use of anaerobic spores as routine indicator. Regarding the control of Cryptosporidium outbreaks, the expectation that a single indicator will satisfy all purposes is unreal. It may be more useful to know the advantages and disadvantages of several indicators, and integrate them appropriately.

A Comparison of Water Quality Indexes for an Inland River

“…By attaching themselves to particulate matter, pathogens reduce their exposure to disinfectants. Studies have shown a strong relationship between removal of turbidity and removal of protozoa [43,44]. In this study, average turbidity values varied between 195.49±65.62 and 94.03±14.74 NTU for the WS and DS, respectively.…”

Performance of slow sand filters in the after-treatment of effluent from Pernambuco state textile center

“…The color of a sample, shown in Figure 4b, indicates the presence of dissolved organic or inorganic matter and refers to the presence of suspended material, being a parameter that can be quickly and easily determined (Heller et al, 2007). Figure 4b shows the study of apparent color for slow sand filters.…”

Avaliação da remoção de Giardia spp. e Cryptosporidium spp. em processos de tratamento de esgoto sanitário

“…Fonte: BASTOS et al, 2003;HELLER;PÁDUA, 2006;USEPA, 1999;WEF, 1996;WHO, 2006. (retirada de MEDEIROS, 2010.…”

“…Entre os microrganismos relatados, Giardia e Cryptosporidium merecem destaque pois são excretados em alta concentração, possuem baixa dose infectante e são resistentes a processos de desinfecção comumente utilizados para tratamento de água e de efluentes (HELLER;PÁDUA, 2006).…”

“…Segundo Heller et al (2007), existe a necessidade de pesquisa em indicadores físicos e microbiológicos para avaliar a eficiência dos processos de tratamento de esgoto quanto à remoção de patógenos.…”