A team of Moroccan researchers have designed an efficient filter system for the treatment of rural wastewater. The system uses layers of soil and gravel which clean domestic waste water, make it suitable for agriculture irrigation.
The multi-soil-layering (MSL) system was successfully tested by scientists of Morocco’s Cadi Ayyad University. The results of the tests carried out on this filter were published last October in the International Journal of Hygiene and Environmental Health.
The filter prototype, tested in the rural region of Al Haouz, near Marrakech, has managed to remove a large amount of waste such as solid particles, organic pollution, nitrogen and fertilizer residue.
The system also kills coliform bacteria and other pathogens in the water including faecal matter, E.coli and streptococci bacteria. The filter system consists of a two-stage process that can be easily assembled with local material in water barrels.
The researchers created filter ‘bricks’ from sandy soil, charcoal, sawdust and iron scraps, and packed these into the barrels with gravel. While running through the barrel, the water is filtered alternatively by the bricks and the gravel.
Laila Mandi, a lead researcher of Cadi Ayyad University, said the soil bricks on their own were good enough to filter organic waste and nutrients from the water. But when combined with the gravel, the two-stage system became effective enough to tackle pathogens.
She said the system could provide cheap and low-tech water filtration to rural, arid areas. “The cost of this technology is very low compared with systems like lagoon filters, wetlands and sand filters,” Laila Mandi said.
It also has benefits such as simple maintenance, no frequent clogging and no energy requirements, she added. The expected lifetime of each filter system, if correctly maintained, is about 20 years
The researchers have meticulously controlled for one year the wastewater quality and checked the efficiency of the system in pollutants removal.
The efficiency of MSL technology to reduce contaminants was not affected by 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.
According to the Moroccan researchers’ team, the two-stage MSL system achieved a high treated wastewater quality for its reuse in agriculture.