August 2010, Vol. 22, No.8

Problem Solvers

Amiad Filtration Systems Filters Water in Waku Kungo, Angola

Problem: The Waku Kungo region of Angola lacked clean water for municipal, industrial, and agricultural uses.
Solution: Build a new water filtration and disinfection plant for the region.

 

According to a 2009 UNICEF report, nearly 8.7 million people in Angola have no access to clean water, resulting in unsanitary conditions and low crop yields.

The water supply for Angola’s Waku Kungo region has been piped in from a spring on nearby Mount Lopupa. This old system had a low flow rate and was built from decades-old asbestos piping. While this technology was deemed appropriate when Waku Kungo’s population was smaller and the use of electricity was limited, the gravity-based system was no longer sufficient to provide either the necessary quality or quantity of water for city residents.

Responding to the need for clean water, a development company called on Amiad Filtration Systems (Kibbutz Amiad, Israel) to design and implement a system to provide clean water to the 50,000 city inhabitants, as well as the 15 villages surrounding the city.

Amiad responded with a water treatment facility that treats the city’s main water supply, the Keve River, by removing suspended solids and providing disinfection. This facility, which cost $500,000, will provide potable water for household, agricultural, and industrial use.

The company recently finished installing the facility and completed its testing phase in late March. The facility is the first combined-use water treatment plant in Africa.

 

Operations and Maintenance at the New Facility
The new water treatment facility is designed to provide clean water at a flow rate of 900 m3/h, with filtration down to 25 µm. Source water for the facility is pumped from the Keve River, which is 20 km from the city. The facility utilizes the Amiad Filtration System, which consists of 150-mm (6-in.) Filtomat series filters with 80-µm filtration capacity and 200-mm (8-in.) EBS series filters with 25-µm filtration capacity.

Generators will supply the facility’s power needs for pumping, filtration, and disinfection. Maintenance of the facility will be operated by local teams that receive training from the development company.

This system was chosen because it uses less water and energy than other systems, providing an ecologically sound, budget-friendly water treatment solution.

Automated Self-Cleaning Screen Filters
The system’s 80- and 25-µm screens self-clean when suspended solids, or filter cake, are detected. The system’s programmable logic control function regulates the cleaning cycle through one of three options: a preset value of pressure differential, a time-interval parameter, or a manual start.

Gradual buildup of dirt on the inner screen surface of the filter causes an increase in the pressure differential across the screen. When the pressure differential reaches the preset value and/or time interval, the self-cleaning mechanism is triggered, and a unique suction scanner begins a flushing cycle.

The self-cleaning mechanism consists of nozzles that spiral across the screen and an exhaust valve that opens to create a high-velocity suction stream at the nozzle tip that “vacuums” the filter cake from the screen. The option of a continuous flush cycle is possible, as the suction scanner cleans small sections at a time while the rest of the filter is still filtering flow.

This cleaning method is fully automated and cleans all of the screen area quickly, using less than 1% of the total process water for cleaning. Compared to other available water treatment options, this system saves up to 75% of the backflush water in the self-cleaning process. This system also can use source water to backflush instead of clean water.

 

Benefits of the System and Future Projects
Because the Amiad system detects shifts in pressure differential, cleaning is initiated according to set parameters measured on-line, reducing the cost of maintenance and amount of energy used when compared to systems that clean only by time intervals.

“We are proud that our system was chosen for this special project, and we are honored to provide much needed clean, filtered water to the citizens of Waku Kungo,” said Arik Dayan, chief executive officer of Amiad Filtration Systems. “Amiad works hard to provide flexible and efficient solutions that are tailored to specific regional and individual needs, and we greatly look forward to providing additional filtration solutions to villages across Africa.”

© 2010 Water Environment Federation. All rights reserved.