Wednesday, 15 August 2012

Using Wastewater for Banana and Biogas Production

Biogas education Southern Africa Zambia

Using Wastewater for Banana and Biogas Production

Extracted from BORDA Southern Africa/ SADC website:


Wherever people live, they need water and wherever water is consumed there is generation of wastewater (or sewage).Wastewater can originate from washing processes or transportation like in flush toilets. It can contain soap residues, organic waste, soil, urine and excreta, animal waste and chemicals.Not all wastewater is per se dangerous. As long as wastewater is untreated, it contains a large quantity of plant nutrients and is therefore both, a source for irrigation and a replacement of other forms of fertilizer.

Using wastewater as opposed to fresh water saves the producer the purchase of other input like artificial fertilizer and/or animal manure. 


Plants will usually respond positive on wastewater (or sewage). Well treated wastewater can deliver a significant and sustainable contribution to food production in Zambia.It is estimated that about 40% of the vegetable produced in Zambia are produced with waste water. It is a common practice to puncture wastewater pipes to get a part of the effluent and grow crops with it.


Extended vegetable fields can be found in the vicinity of sewage treatment installations. The sewage flowing through the vegetable field in Chamba Valley, Lusaka  comes straight from a sewage pond. Peasant farmers grow maize, pumpkin, sweet potatoes, cassava, banana, rape and many other vegetable crops.


Wastewater should not flow untreated in rivers or water bodies. Many people may exist downstream and need the water for their living. Dirty water can easily spread diseases.


Decentralized Wastewater Treatment


WASAZA promotes and pilots DEWATS (Decentralized Wastewater Treatment Solutions) In Zambia. The objective is to turn something that is considered negative into several “positives”.      


The centre of the treatment system is a biogas plant or in other words a bio digester.


It digests organic matter into 

•    Biogas which is piped into the kitchen and used as cooking gas

•    Water, partially treated, which can be used for irrigation

•    Sludge which can be dried and used as compost soil.

The post treatment is done in a planted gravel filter which can be planted out for instance with flowers and banana. After this process the wastewater has lost its smell and danger for spreading diseases.


The most prominent DEWATS build by WASAZA in conjunction with its partner BORDA (Bremen Overseas Research and Development Association) is in eastern Lusaka at Pestalozzi School at Ibex Hill. It treats the wastewater and the organic kitchen waste of the boarding school, generates biogas for the kitchens and wastewater for the students garden for irrigation.  


WASAZA has also provided the technology for wastewater treatment for the low cost housing compounds in Kariba (Ndola), Libuyu (Livingstone) and,   Kandundu, (Solwezi). The community which was formerly confronted with pathetic sanitation conditions, is now having flush toilets and some of them can enjoy the biogas generated from the wastewater and do not need charcoal any longer for their cooking. The project was organized by Devolution Trust Fund (DTF) and executed by the respective Commercial Utilities.


The abattoir waste on Fringilla Lodge is not contaminating the farm surrounding any longer, but generates energy for the restaurant kitchen and the slaughtering process.


The big slaughterhouse in Kalomo will soon generate gas for a restaurant from the wastewater generated from slaughter operations.


Waya School near Kabwe has been equipped with a bio latrine. 450 students have better toilet facilities and the food for the 80 most vulnerable students is cooked on the energy generated from the toilet waste. The project is done in cooperation with BOCCS (Buyantanshi Open Christian Community Schools), Munich Advisors and Share for Smiles.


Mubanga and Jonathan Sim High school in Kalomo District are equipped with several DEWATS for the dormitories. Gas will be used in the school kitchens, the effluents will support gardening. The project was done in cooperation with World Vision Zambia.


Kapapa farm, south of Choma is equipped with an agricultural biodigester and 4 biolatrines for 6 households of farm workers each (total 24 toilets). All 24 households will soon cook on biogas as the gas from the large digester will feed into the biolatrines and will be distributed to the households from there. The project is implemented with Southern BioPower, Lusaka.


Chishembela farm treats piggery waste with 5 large biogas plants. The system will help to minimize odor disturbances and produce at the same time large amounts of energy to keep the fish ponds at a constant temperature.


Among others WASAZA plans with its partners and clients within this year  DEWATS for St. Paul’s Hospital in Kashikishi, Cheshire Orphanage in Kaoma. Fecal sludge treatment digesters in Kanyama and Water Hyacinth digesters in Livingstone providing energy for the hotels 


Biogas for cooking and banana plantations in planted gravel filter fed from treated wastewater are becoming popular in Zambia 

Marisa Naude