The Steuben Lakes Regional Waste District (SLRWD) has modernised the Waste District Wastewater Treatment Plant in Angola. The SLRWD has installed new filters in the plant to improve its operation to 9,092.18 m3 per day.
The SLRWD has also equipped the plant with a “more efficient filtering system that is less sensitive to weather-related disturbances The new filter system installed at the Waste District’s wastewater treatment plant uses a fabric media suspended on large rotating discs. These allow the plant to filter and remove all solids from the wastewater that has been treated and is ready to leave the plant.
According to SLRWD, prior to the rehabilitation project, the Waste District Wastewater Treatment Plant used a large two-stage settling tank that simply allowed solids to settle to the bottom of the tank as it passed. These settled solids then accumulated over time, producing ammonia and hydrogen sulphide gas that polluted the water before it left the treatment plant.
The new filtration system installed includes a levelling basin equipped with two pumps. This water is then purified using two fabric disc filters. Each filter has a flow rate of 4,546.09 m3 per day. “A chemical feed system finally removes phosphorus from the water using polyaluminium chloride, unlike the old system which used ferrous chloride. The polyaluminium chloride system provides more efficient phosphorus removal and reduces the use of chemicals by about 40%,” explained the SLRWD.
Financing the upgrade
The government of Angola provided US $2.5m for the upgrade of the treatment plant which was 68% of the overall cost that was estimated at US $3.7m. The wastewater treatment plant upgrade took nine months to complete.