Ferric sulphate flocculation as a concentration method for Giardia and Cryptosporidium in filter backwash water

Filter backwash water (FBW) is a prominent residue from water treatment plants (WTPs) that is often disposed into water bodies or recycled within the WTP without due disinfection. FBW usually contains particles within a size range that includes pathogenic protozoa, as the infective forms of Giardia and Cryptosporidium, parasites responsible for waterborne diseases outbreaks. Quantifying (oo)cysts is essential for addressing this matter, as it might assist research on giardiasis and cryptosporidiosis epidemiology, as well as shed light onto disinfection technologies for FBW. However, (oo)cyst recovery from FBW and other complex matrices still lacks a standard protocol and entails specialized professionals and expensive material. Seeking to provide insight in a reduced-cost recovery method, this study analysed the recovery efficiency (RE) obtained by acid flocculation with ferric sulphate, a common coagulant, on bench-scale simulated FBW. Steps included concentration by flocculation, centrifugation, and quantification by immunofluorescence. Although recovery was sufficient for Cryptosporidium parvum (40.59%), Method 1623.1 recommendations were not reached for Giardia muris (1.76%). Coefficients of variation obtained for both organisms were not satisfactory, highlighting the variability to which environmental matrices are subjected and why defining a methodology for (oo)cyst recovery in WTP residues is important.

The efficacy of a recovered wash water plant in removing cyanobacteria cells and associated organic compounds

The treatment works under investigation uses a recovered wash water plant (RWWP) to remove impurities prior to recycling filter backwash water. Filter backwash water (raw water) is characterized by high quantities of cyanobacteria cells and associated organic compounds; a potential threat when recovered water is recycled. The aim of this study is to identify the cyanobacteria cells and associated organic compounds in the filter backwash water and to subsequently evaluate the effectiveness of the RWWP in removing these organic impurities during the following periods; autumn-winter and spring-summer. Results showed that at least six major phytoplankton groups were present in the filter backwash water with turbidity levels (59 and 46 NTU; autumn-winter and spring-summer, respectively) being much higher than the drinking water productions standard of ≤5 NTU. Cyanobacteria were a dominant group (mean of 80% and above) in the total phytoplankton composition of the raw water and consisted of three genera (Anabaena sp., Microcystis sp. and Oscillatoria sp.), which were effectively removed by the RWWP (up to 99%). However, associated organic compounds such as geosmin, total organic carbon (TOC), dissolved organic carbon (DOC) and microcystin were not effectively removed during the different seasonal periods but were of such low concentrations that they posed no major risk to the drinking water quality, meeting the RWWP water quality standard.

Physicochemical, microbiological and parasitological characterization of the filter backwash water from a water treatment plant of Blumenau - SC and alternatives for treatment and reuse

Filter Backwash Water (FBW) from water treatment plants (WTP) is composed of raw water waste, chemicals and microorganisms. Inappropriate disposal of this residue impacts negatively in the environment and in the health of human populations. Aiming to characterize the FBW from one WTP of Blumenau-SC, physiochemical, microbiological and parasitological assessments and tests with different flocculants polymers were performed in order to propose strategies for treatment and reuse of this residue. Subsequently treated liquid is discharged into the Itajaí-Açu River (Class 2). Physicochemical and microbiological analyses showed results higher than those permitted by CONAMA Resolution n° 430/2011 and Giardia duodenalis (Assembly B) cysts and Cryptosporidium spp. oocyst positivity was observed, characterizing as polluted and contaminated residue that shouldn't be released in the hydric body. The anionic flocculant polymer showed satisfactory results in the turbidity sample reduction (99.49%), which may be a promising alternative in the treatment of this residue.

Influence of spent filter backwash water recycling on pesticide removal in a conventional drinking water treatment process

The effects of recycling spent filter backwash water (SFBW) on the removal of 14 organic pesticides were examined in a simulated conventional drinking water treatment process.