The City of Cape Town’s Mayoral Committee has approved two major construction contracts linked to the R5-billion upgrade of Potsdam Wastewater Treatment Works (WWTW).

The upgrade of the WWTW will increase capacity from 47-million litres of treated wastewater a day to 100-million litres a day, with membrane technology incorporated to ensure high wastewater treatment standards.

“With the tender appeals dismissed, all that remains is a 30-day statutory public participation before the contracts can be awarded,” said Cape Town Mayor Geordin Hill-Lewis, adding that the City Council is expected to approve the projects on March 29 during a final statutory public participation.

A Section 33 Municipal Finance Management Act public participation process is required for projects exceeding three years before entering into a contract with a service provider.

The Potsdam upgrade project is split into two components in the upgrade and expansion of the Potsdam WWTW, namely the mechanical and electrical tender for the design, supply, installation and commissioning of mechanical and electrical infrastructure and the civil tender for the civil construction of infrastructure and buildings, including demolition works.

“Construction is set to start in May on the Potsdam upgrade if all goes to plan. We will monitor this upgrade closely to ensure it stays on track,” he said, noting that multibillion-rand upgrades to Potsdam, the surrounding sewer network and pump stations were a major step towards restoring the health of Milnerton Lagoon.

“Consultants are also due to complete their study on short-term interventions to improve lagoon water quality and odour, including options to potentially aerate or bio-remediate the lagoon.”

The City aims to steadily close off pollution sources to the lagoon, building up to the ultimate goal of dredging and removing the sediment at the bottom, along with decades of pollution build-up.

Hill-Lewis said the City’s upcoming 2023/24 Budget proposes R8.6-billion in capital upgrades to wastewater treatment works over three years, alongside R1.4-billion in bulk sewer upgrades to the Milnerton, Cape Flats, Gordon’s Bay and Philippi lines.

Meanwhile, work is nearly complete on the re-engineering of natural reed beds adjacent to Potsdam WWTW to prevent polluted stormwater from reaching the Diep river.

“The reed beds are now better able to retain this stormwater through raised walls and valve installations. Historically, the reed beds acted as natural filters for pollution in stormwater before it reaches the Diep river. Now the polluted stormwater can be largely retained, and pumped back to Potsdam for treatment,” he explains.

Major work to drain and clean maturation ponds at Potsdam is also under way, with completion expected by June.

“Effluent is meant to be retained in these ponds before release, but pollution build-up in the pond sediment has prevented this. As a result, the ponds are currently being by-passed using pumps as far as possible.”

Once cleaned, the ponds will be able to retain final effluent, before a final UV treatment of effluent prior to release into the Diep river. This is set to have a significant positive impact on effluent quality.