Two-stage vertical flow multi-soil-layering (MSL) technology for efficient removal of coliforms and human pathogens from domestic wastewater in rural areas under arid climate

Lahbib Latrach; Naaila Ouazzani; Abdessamad Hejjaj; Mustapha Mahi; Tsugiyuki Masunaga; Laila Mandi

doi:10.1016/j.ijheh.2017.10.004

Two-stage vertical flow multi-soil-layering (MSL) technology for efficient removal of coliforms and human pathogens from domestic wastewater in rural areas under arid climate

Int J Hyg Environ Health. 2018 Jan;221(1):64-80. doi: 10.1016/j.ijheh.2017.10.004. Epub 2017 Oct 13.

Authors

Lahbib Latrach¹, Naaila Ouazzani¹, Abdessamad Hejjaj², Mustapha Mahi³, Tsugiyuki Masunaga⁴, Laila Mandi⁵

Affiliations

¹ National Center for Research and Study on Water and Energy (CNEREE), Cadi Ayyad University, PO Box: 511, 40000, Marrakech, Morocco; Laboratory of Hydrobiology, Ecotoxicology and Sanitation (LHEA-URAC33), Faculty of Sciences Semlalia, Cadi Ayyad University, Marrakech, Morocco.
² National Center for Research and Study on Water and Energy (CNEREE), Cadi Ayyad University, PO Box: 511, 40000, Marrakech, Morocco.
³ International Institute for Water and Sanitation, National Office for Electricity and Potable Water (ONEE), Rabat, Morocco.
⁴ Faculty of Life and Environmental Sciences, Shimane University, Matsue 690-8504, Japan.
⁵ National Center for Research and Study on Water and Energy (CNEREE), Cadi Ayyad University, PO Box: 511, 40000, Marrakech, Morocco; Laboratory of Hydrobiology, Ecotoxicology and Sanitation (LHEA-URAC33), Faculty of Sciences Semlalia, Cadi Ayyad University, Marrakech, Morocco. Electronic address: mandi@uca.ma.

PMID: 29042198
DOI: 10.1016/j.ijheh.2017.10.004

Abstract

This paper investigates the removal efficiency of organic matter, nitrogen, phosphorus, coliforms and pathogens from rural domestic wastewater in a two-stage vertical flow multi-soil-layering (MSL) system. The effects of wastewater quality, season and arid climate conditions on pollutants removal efficiency by the system were examined for one year. The experimental setup included two similar MSL systems composed of two layers: soil-mixture-layers (SML) and gravel permeable layers (PL) that are arranged in a brick like pattern. The applied hydraulic loading rate was 1000Lm^-2day^-1. Results showed that most of the physicochemical contaminants elimination occurred while the wastewater percolated through the first MSL stage. The second stage demonstrated an improvement in the reduction of all pollutants, especially fecal bacteria indicators and pathogens. The mean overall removal rates performed by the two-stage MSL system were 97% for TSS, 96% for BOD₅, 91% for COD, 96% for TN and 95% for TP. For bacterial indicators, the combination of two-stage MSL system achieved high log removals between 2.21 and 3.15 log units. Contaminants reduction processes in MSL technology are more dependent on internal than external environmental factors. The effectiveness of the two-stage MSL system to treat domestic wastewater was strongly influenced by wastewater quality. Significant relationships between influent contaminants level and their removal efficiency were found. The efficiency of MSL technology to reduce contaminants is not sensitive to season and air temperature fluctuations. This is due to the capacity of MSL system materials to withstand the air temperature variation, which highlights one of the advantages of MSL's technology. Wastewater quality is the most important factor affecting the removal of contaminants in the MSL, which could be a critical parameter to considered when designing MSL system. Two-stage MSL system achieved a high treated wastewater quality amenable for treated wastewater reuse in agriculture recommended by Moroccan code of practice. Therefore, the combination of two-stage vertical flow MSL system could be considered an efficient and promising domestic wastewater treatment solution in arid countries to promote environmental protection and wastewater reuse.

Keywords: Fecal bacteria; Nutrients; Organic matter; Pathogens; Rural domestic wastewater; Two-stage vertical flow multi-soil-layering system.

Publication types

Evaluation Study

MeSH terms

Enterobacteriaceae / isolation & purification*
Rural Population
Water Microbiology
Water Purification / methods*
Water Quality