Welcome to Nakuru Defluoridation Company Ltd

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1      Institutional filters



The institutional filters are recommended where the water consumption for drinking and cooking is between 50 to 500 L per day.

The inflow to the institutional filter is connected to the water supply system and controlled by a ball valve. A flow meter shows the exact amount of water that has passed through the filter. The filter consists of a standard PVC tank (650 L), containing ~ 450 L of bone char of different sizes: Middle size bone char (0.63 - 2 mm) at the top (330 L) and coarse bone char (2 - 4 mm) at the bottom (120 L). Ballast at the bottom of the filter enables the drainage of the treated water, which is then collected in PVC pipes. These pipes contain cuttings, turned towards the bottom of the filter, where the water can enter. A nylon mosquito prevents the wash-out of the bone char into the drainage layer and hence prevents clogging of the system (see Figure 2‑1). Due to the raised outlet, the filter medium is always saturated with water and hence never dries up. Depending on the wishes of the customer, the filter outlet can either be connected to a supply system, which for instance serves a kitchen with defluoridated water or it is connected to a tap where the people can withdraw defluoridated water.



The institutional filter costs KES 150,000 excluding the installations to the water supply system and/or a desired connection to the household.




Figure 2‑1: Sketch and picture of an institutional filter.


No daily maintenance is required as the operation does not differ from using a standard water storage tank. After a certain time, the bone char is saturated and has to be regenerated (see “Draft on CDN’s experiences in producing bone char”). Based on the fluoride concentration in the raw water, estimations on the amount of treatable water can be given. The flow meter then indicates the time when the filter material has to be regenerated.