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Friday, 14 March 2014 11:07

Tanzania: Scientists Embark On Green Water Recycling Technique

By Salvatory Mushi and Sharifa Kalokola

DAR ES SALAAM, Tanzania, March 14, 2014 (TDN) -- Tanzania scientists are exploring an affordable innovation, constructed wetlands technology, for treating and reusing waste water for agriculture.

A constructed wetland is a shallow pool 0.6 meters deep, filled with limestone or gravel of different sizes designed to cleanse water that create growing conditions for plants. Vegetations like Phragmites grasses that remove pollutants are planted on the pond.

Features of artificial wetlands mimic those of the natural swamps and ponds but do not replace their functions.

As the debris from septic tanks seeps into the limestones, contaminants are filtered. Once the water reaches the root zone of wetland plants, micro-organisms in the soil destroy disease causing organisms-pathogens. The cleansed water is then channelled either into a pond, drainage or piped back to be re-used.

'This technique addresses water scarcity and shortage of fertilisers in agriculture,' says Prof Jamidu Katima from the College of Engineering and Technology, University of Dar es Salaam.

The lead researcher of the project says that the waste water contains rich plant nutrients; phosphorous and nitrogen, that flourishes crops like rice, maize, tomato and beans. In the project, the scientists use water from the pond for irrigating farms and fish farming. The research is currently happening in Morogoro. The Municipal Authority owns and maintains the ponds.

Prof Katima's research group has dispelled doubts regarding health dangers resulting from eating fish from the constructed wetland's pond.

The research group has health experts who monitor the quality of both fish and agricultural produce to ensure they don't cause health risks to human health.

Studies on constructed wetlands started way back in 1995 as collaborative research projects between the Royal Danish School of Pharmacy, University of Copenhagen, the Engineering Academy of Denmark and the University of Dar es Salaam. The Danish government was initially the main sponsor.

The Tanzanian Commission for Science and Technology in Tanzania (COSTECH), the government organisation that co-coordinates and promotes research and technology development activities, is currently the project funder. The organisation has also the role of disseminating research results to the public.

'This is the first time for our research group to receive government's money. With this opportunity, we aim to convince the government to incorporate this technique in water treatment systems,' Prof Katima adds, "We did a similar study previously in Moshi, now we are in different settings to duplicate results and gain confidence on this technique."

Tanzanian sanitation authorities currently use water standardisation ponds to treat waste water. The wastewater stabilisation ponds are shallow lagoons, one to two meters deep, built in series where raw sewage is treated by natural processes involving algae and bacteria.

While these ponds offer the primary treatment of raw sewage, constructed wetlands ponds offer an eco-friendly option of secondary treatment by further polishing the wastewater, so that it can be used for fish farming or recycled for other human uses, according to the academics.

Both of these lagoons, however, may provide a breeding area for mosquitoes and may produce an offensive smell if not properly maintained.

The academics have promoted constructed wetland technology in schools, hospitals and industries. The technology has proven handy in Iringa girls and Ruaha secondary school.

Adriano Akioo, former wetland co-ordinator at Ruaha Secondary School says that the technique saved the school from cost of emptying the septic tanks.

'We used to empty the septic tanks four times in a year since we had 700 students. But with the help of scientists, we managed to build a wetland that reduced school's expenditure,' he says.

Akioo says that the cleansed water is used to irrigate animal feeds.

"The water from the wetland is unsoiled and odourless. Staff workers use it for watering their gardens," he says.

The scientists have also applied the technique at industrial level at the Arusha winery. The winery lets the effluent into the biogas digester that produces electricity and then channels the remaining waste into the constructed wetlands.

The academics have been consulted to develop the ponds in Kenya, Madagascar and Comoro.

'Houses located in areas with high water table can apply this method since septic tanks fill up quickly in such areas. I advise communities to team up and build one wetland for many houses,' Katima urges.

Constructed wetlands technology is old nevertheless unpopular, according to Prof Katima. This year the 14th constructed wetland conference will be held in China. The last one was hosted in Tanzania.

*This article was orginally published by Tanzania Daily News.


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