Civil Designer Showcase

GATEWAY TO BOOM TOWN

EAST London is literally buzzing with the latest activities in waste water treatment projects and Victor de Wet at Arcus Gibb is currently in high demand. With an Honours degree in water utilisation engineering, Victor is regarded as an expert in water treatment design and thrives on the challenge of providing his designs in an integrated system.

"One of the unique features of a treatment works design is that any design change seems to have the most amazing ripple effect. In fact, one design change can change up to 10 different drawings at a time. That is why Civil Designer is such a pleasure to work with because it identifies potential clashes and you can update the design in a matter of seconds," explains Victor.

Two of the projects that Victor is currently working on include the Maclear and Peddy Wastewater Treatment Works (WwTW). "The Maclear and Peddy WwTW has a size of 1,4 and 2 million litres respectively and is a multidisciplinary project encompassing various aspects such as the biological process, unit process, hydraulics, structural, water reticulation, road & stormwater terrace design as well as the checking of pipe clashes throughout the whole interlinked system."

"Ukatlamba District Municipality is the water service authority for Maclear WwTW with the water service provider being Elundini Local Municipality and this venture has a total estimated value of approximately R18 million for each project," notes Victor.

Victor goes on to explain the involved process of the design. "When I began working on the assignment in April, I started by designing the platforms and pond to balance the cut and fill volumes and spent a large portion of my time on the unit process and hydraulics design. The structures for the WwTW consist of an inlet works, reactor (comprising of an anaerobic, anoxic and aerobic zone), a sedimentation tank, chlorine contact tank, a thickener, sludge drying beds and the relevant recirculation and waste pumps."

"Basically, the raw sewage enters the WwTW through the inlet works which removes the solids and grit from the water. From here the screened sewage flows through the reactor where the biological process takes place and then goes through the sedimentation tank where the solids are separated from the water by gravity settling. The clear water is then disinfected with chlorine and flows through the channelled chlorine contact tank to ensure sufficient disinfection time before the water is discharged into the Mooi River."

"Finally, the settled activated sludge from the sedimentation tank is recirculated back to the reactor to ensure the desired concentration of organisms in the system to clean the water. Sludge also has to be wasted to the drying beds to control the concentration of sludge to the reactor and the wasted sludge is then thickened in the thickener to a fifth of its volume," he explains.
 
Maclear & Peddy WwTW | Arcus Gibb


But what happens to the dried material and the level of waste when addressing pollution levels? According to Victor, the sludge from the thickener "feeds to a sludge pump station and then gets pumped to drying beds to dry out. The dried sludge material, which oxidates to a non-toxic state will then be distributed to farmers as fertiliser, leaving almost no waste."

In cases of power failures a unique buffer against pollution is provided. "We provide a lined earth dam after the chlorine contact tank. This earth dam is also linked to a pump station which could pump the contents from the earth dam back to the inlet works to help with pollution" says Victor.

According to Victor, one of the biggest challenges when you are dealing with a treatment works assignment is to ensure that everything works together as a unit and that no detail is left unchecked. "When you work with a program like Civil Designer it simplifies this task tremendously. You can create a virtual model of what is on site so that you get an accurate picture of what the obstacles are. As an engineer, this gives you a great sense of peace and once you have explored all the options, you can set about with your design in AllyCAD and the output is really quick," he says. The Maclear WwTW development project is currently under construction and is likely to be completed in March 2007.

In the last year Victor has worked on two extensive waste water treatment works projects and each one has remained uniquely different to the next. With the next venture lurking in the not too distant future, there is little opportunity for a rest and Victor's office will no doubt get a lot busier in the boom town of East London.


 
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