Removal of contaminants and pathogens from secondary effluents using intermittent sand filters

Abstract

Intermittent infiltration percolation of wastewater through unsaturated sand bed is an extensive treatment technique aimed at eliminating organic matter, oxidizing ammonium and removing pathogens. The main purpose of this study was to determine the depuration efficiencies of a sand filter to remove contaminants from secondary wastewater effluents. Elimination of pathogenic bacteria (total and faecal coliforms, streptococci) and their relationship with the filter depth were investigated. Results showed a high capacity of infiltration percolation process to treat secondary effluents. Total elimination of suspended solids was obtained. Mean removal rate of BOD(5) and COD was more than 97 and more than 81%, respectively. Other water quality parameters such as NH(4)-N, TKN and PO(4)-P showed significant reduction except NO(3)-N which increased significantly in the filtered water. Efficiency of pathogenic bacteria removal was shown to mainly depend on the filter depth. Average reductions of 2.35 log total coliforms, 2.47 log faecal coliforms and 2.11 log faecal streptococci were obtained. The experimental study has shown the influence of the temperature on the output purification of infiltration percolation process.

The effect of sub-irrigation with untreated and treated municipal wastewater on organic matter and Nitrogen content on two soil types

“…An ammonium increase was also observed by Qian and Mecham (2005) when soil was irrigated with wastewater. When urban wastewater was applied in columns of an unsaturated sand layer, NH4-N was showed a significant reduction, (Bali et al, 2011) and according to Nola et al (2006) NH4 + was withheld up from 97.37 to 98, 74% in the soil profile. In clay soil NH4-N concentrations decreased after sub-irrigation with wastewater and this could be attributed to NH4-N nitrification and fixation within clay, and to NH3 volatilization (Jiajie, 2013).…”

“…According to Yadav et al (2002) nitrates concentration contained in untreated wastewater are much lower than in treated one. According to Bali et al (2011) and Jiajie (2013), an increase in NO3 -N in filtered water was observed, when wastewater after secondary treatment was applied in an unsaturated sand layer. In addition, nitrates increased in full depth of the soil (sandy, clayey, limestone-clayey).…”

“…When SL and LS soils were compared for the same treatment, total N% was statistically significant only in control treatment (Wα Vs Wβ) (p  0.032) (see Yable 7). Qian and Mecham (2005), Galavi et al (2010), Bali et al (2011), Abegunrin (2016), and Jiajie (2013) found that during irrigation with wastewater there was a significant increase in total N % (p ≤ 0.05) and according to Alrajhi (2015) total N% increased by 4 %. This could be explained by the fact that wastewater addition to soil increases nitrogen concentration (Monnett et al, 1996;Fuentes et al, 2002;Cooper et al, 2015) which could be attributed to urea and nitrogen contained in the urban wastewater (Bernala et al, 2006;Fonseca et al, 2005a).…”

Electrical Conductivity, pH and other soil chemical parameters after sub-irrigation with untreated and treated municipal wastewater in two different soils.

“…On the whole, total % of phosphorus increased in soil after irrigation with treated wastewater. Therefore, PO 4 -P showed a significant reduction in filtered water of an unsaturated sand layer, when secondary treatment wastewater was applied (Bali et al, 2011).Regarding soil columns, PO 4 concentration was lower in the effluent than in the applied wastewater contained, indicating its retention in soil profile (Chahal et al, 2011). Moreover, phosphorus was reduced by 30% in a thick limestone layer (vadose zone-9 m) when secondary treated wastewater penetrated it (Bekele et al, 2011) and it was removed by 94% (53 tones) in an area (100 hectares) irrigated with wastewater (Kadlec, 2009).…”

Removal of phosphorus from secondary effluents using infiltration–percolation process

“…Infiltration-percolation is a commonly used treatment process which is capable of oxidizing and decontaminating wastewater (Mottier et al 2000;Eturki et al 2011;Bali et al 2010). It has been developed as tertiary treatment of secondary effluents in several Mediterranean countries (Auset et al 2005;Bali et al 2011). It can be used as an alternative method for phosphorus removal.…”