Processing Tertiary Treated Sewage Effluent for Reuse
We produced a turnkey water treatment system for an industrial company in the Klein Karoo that was looking to process tertiary treated effluent for reuse.
Our client, a manufacturer in Oudtshoorn in the arid Klein Karoo area, required a custom water treatment system that processes a significant volume of tertiary treated municipal water to a usable, potable standard for reuse at their facilities. Specifically, the standards that had to be met are Guidelines for Drinking-water Quality as set out by the World Health Organisation (WHO).
We commenced by performing comprehensive water testing to determining the main concerns regarding water quality.
The tests showed that the main factor we had to take into consideration was the anticipated fluctuation in the raw water quality.
Design and Manufacture
Our team of water treatment specialists designed and manufactured a system that purifies the water in multiple stages.
These stages are:
Reverse osmosis (RO)
The pre-treatment stage consists of a combination of coagulation, pH adjustment and oxidation. This facilitates the efficient precipitation of dissolved metals, organics, and microbial content.
In order to increase the ultrafiltration membranes' lifespan, a screening stage had to be introduced before proceeding to the filtration stage.
Our screen of choice was the Helix Automatic FT200 AA DLP disc filter, one of the most sustainable disc filters on the market. It ensures that the particles in the water are filtered down to 25 micron, followed by automatic backwashing using a combination of water and compressed air.
The filters used in the filtration stage are ultrafiltration modules and media filters, followed by chemical dosing before the water enters the storage tank.
Firstly, ultrafiltration deals with any fluctuations the water may have. It offers filtration down to 0,08 micron and can produce filtrate at turbidity of 0,10 NTU. The next filtration stage, media filtration, assists in the removal of suspended organic matter from the water.
Reverse osmosis stage
The next stage of treatment consists of reverse osmosis. RO technology – A RO feed pump and high-rejection RO membranes – removes dissolved ionic species in order to achieve the required final product water quality. The RO unit operates at a high recovery rate of 75%.
Post treatment stage
The final stage comprises of disinfection and pH adjustment. In terms of disinfection, sodium hypochlorite dosing will keep biological growth at bay through to point of use. This is followed by sodium hydroxide dosing to maintain a slightly higher pH to prevent corrosion.
Today, the product water consistently meets the World Health Organisation's standards for water quality. As such, the manufacturer is able to reuse the water daily in various manufacturing and cleaning processes at their facilities. Contact us if you would like more information on this project.