Waterberg-Okakarara Water Supply Scheme – Waterberg Purification Works

 

AGF: Autonomous Gravity Sand Filter

Client: NamWater – a commercial entity owned by the Namibian government. 
Industry: Water Supply Scheme
Region: Okakarara, Namibia
Product: 3 x AGF – Autonomous Gravity Sand Filters, Model ASF-42S, 7 MLD capacity
Installation: 1988

Challenge

  • The Waterberg-Okakarara Water Supply Scheme provides water to Okakarara and rural communities in the Waterberg Area. These communities are utterly dependent on this source of potable water. 
  • The groundwater is supplied via an open canal to the Waterberg Purification Works, where suspended solids need to be removed efficiently enough to meet drinking water standards.
  • Many challenges had to be overcome in this rural area – including the remote rugged location, no electricity supply and a lack of local skills.

Application

  • Polishing filters for NamWater Waterberg Purification Works for the removal of fine suspended solids from the water to provide potable water.

Solution

  • The design engineers from Lund Consulting Engineers (LCE) CC relied on the technical expertise of the Superior Filtration team to help them to find the right solution. 
  • Three identical Superior Filtration ASF42S mechanical self-cleaning valve-less Autonomous Gravity Sand Filters (AGF) with a 7 MLD capacity each, connected in parallel, were installed in 1988.
  • Factors taken under consideration:
    • Ease of Installation (reducing capital outlay)
      • Minimum civil works on site.
      • Filters are transported to site and installed in place with limited mechanical assembly.
    • Zero Energy Consumption.
    • Human Intervention Limited to periodic maintenance inspections.
    • Completly Autonomous Function i.e. automatic backwash, no backwash pumps, no human inputs, no external controls.
    • Low Maintenance with virtually no downtime due to high reliability and efficiency.

Results

  • The filters were installed and commissioned easily and rapidly despite the remote location .
  • After 35 years of continuous and autonomous operation, the AGF Autonomous Gravity Sand Filters are still producing high quality filtrate with extreme reliability, even in the harshest conditions. 
  • The AGF filters continue to operate smoothly and entirely autonomously, without any electricity, human intervention or downtime.
  • Since 1988, the filters have only been maintained once – to replace the sand. No other maintenance, upkeep or spares have been required, thanks to the high durability of these filters.

Client Quote

“These filters are very efficient, operating with a mere 1.2 m to 1.5 m head loss, doing so entirely without any outside energy supply, and even backwash takes place without the need for backwash pumps and valves.”