Domestic wastewater disinfection by combined treatment using multi-soil-layering system and sand filters (MSL-SF): A laboratory pilot study

- A conceptual model of multi-soil-layering system and sand filter is proposed.
- Fecal indicators and helminthes eggs were highly reduced.
- A good operational stability and high contaminant removal efficiency were noted.
- Low applied hydraulic loading rate was recommended.
- Treated wastewater could be reused in agriculture practice.

This study aims to present the removal of bacterial indicators of fecal contamination and parasites in a combined treatment using a multi-soil-layering system with sand filters (MSL-SF). This experiment was carried out in a laboratory scale. The MSL pilot (height 65 cm, width 36 cm, depth 30 cm) was composed of soil mixture layers (SML) and gravel layers that are arranged in a brick-layer like pattern. The soil mixture layers are composed of local sandy soil mixed with sawdust, metal iron and charcoal at the ratio of 70, 10, 10 and 10%, respectively, on a dry weight basis. The applied hydraulic loading rate (HLR) was 200 L m−2 day−1. The experimental sand filter included three parallel similar sand columns (inside diameter 12.5 cm, height 120 cm). Each column was filled with 80 cm of fine sand and 10 cm of gravel in the top and the bottom of the filter. Three sand columns HLRs (100, 200 and 400 L m−2 day−1) were compared. The obtained results indicated that the conceptual model based on the combination of the MSL method and sand filter (MSL-SF) showed very high efficiency in organic matter, nutrients, bacteria and the reduction of parasites. The high performances were noted in the low HLR. The main removal percentage of SS, BOD5, COD, TN and TP were respectively 99.73, 97.78, 98.40, 92.93 and 96.21% for the HLR-100. In addition, the Log10 removal for total coliforms, fecal coliforms and fecal streptococci were 4.46, 4.47 and 4.13 Log unit respectively. MSL-SF is capable of removing 100% of helminthes eggs. The MSL system is an efficient method, especially for organic matter and nutrients (N, P) removal. Sand filters have experimentally been proved to be useful for fecal indicators and the removal of parasites. Good operational stability and high contaminants removal efficiency of the combined systems were observed. Therefore, the combination of the MSL system and sand filter offer a good alternative option for agricultural wastewater reuse.