The City of Johannesburg (Co) has introduced the Blue Economy programme that is aimed at taking stock of the critical challenges that the City is facing. The Blue Economy is about generating jobs, responding to basic needs and ensuring that growth is generated into the local economy. This programme allows the City to design a profound impact on economic and social development using locally available resources. The methodological process (scan, screen and implement) covers basic needs like water, food, housing, energy, health, mobility, jobs, ﬁnance, waste management and education and links everything into a comprehensive model. Johannesburg Water has commenced two projects in support of the Blue Economy brigade, the installation of in-pipe turbines and the replacement of 9 litre toilet cisterns with 4.5 litre cisterns.
The installation of In-pipe turbines entails reduction of minimum night-flow (leakage rate at night) and harness renewable energy from the water flowing through our pipe system at strategic locations. Taking advantage of the opportunities presented by our investments in renewable energy.
The replacement of the 9 litre toilet cistern with a 4.5 litre cistern is linked to the water conservation initiative and the pilot project will commence in Soweto.
Energy intensive technology, as used in activated sludge plants, will become unaffordable and a scarce resource in meeting the future demands of the high technology driven wastewater treatment market and this will impact on the economy, environment, health services and social activities in Johannesburg. Energy therefore has become a key driver in the Municipal wastewater services value chain and the City of Johannesburg (CoJ) has recognised the use of biogas as a means of contributing to the Green Economy, which forms part of the New Growth Path of National Government.
Johannesburg Water (JW) manages operates and maintains six wastewater treatment Works (WWTW) on behalf of the CoJ for the central Gauteng region. Followed by the new wastewater Sludge Utilisation and Disposal Guidelines promulgated by the Department of Water and Sanitation in March 2006, Johannesburg selected anaerobic mesophilic digestion as most economical and sustainable process. Besides the process producing a compliant and well stabilized end product, biogas is also produced, which is the essential fuel for Combined Heat and Power (CHP) production.
The initial installation at Northern WWTW was completed in 2012 and is capable of producing 1.1MW of power for the waste water treatment plant, around 12.5% of the waste water plant’s power requirements.
The impact of the installation is the production of 1.2 MW-e renewable electricity and a reduction in emission of 10 000tCO₂. Since inception in 2012 4,385MWh electricity was generated with 4,516 tons of CO₂ Green House Gas offset.
Furthermore, the Northern WWTW was the first of Johannesburg’s six wastewater treatment facilities to undergo expansion and upgrade to improve sludge digestion and comply with the Department of Water Affairs’ South African Guidelines for Wastewater Sludge Handling and Disposal. Johannesburg Water opted to implement biogas collection and storage facilities at the Northern WWTW. The high energy costs that were being experienced, coupled with the increase in biogas production from the high performance digestion facilities, presented Johannesburg Water with the unique opportunity of implementing a biogas to energy project. The use of cell lysis technology in the application of biogas to energy for a WWTW facility is certainly unique in South Africa. This has increased the efficiency of the overall biogas to energy system and saved on electricity costs for Johannesburg Water.
The South African Institution of Civil Engineering (SAICE) awarded Johannesburg Water as the winner of the 2012/2013 Most Outstanding Civil Engineering Project Achievement in the category: Technical Excellence projects for the Biogas to Electrical Energy project.
Driefontein WWTW was upgraded to a 55Ml/d facility with the installation of digestion as part of the upgrade. Commissioning of the wastewater treatment facility is in testing phase. The second biogas to energy installation was part of this upgrade and is nearing completion and included two CHP units of 376kW electrical power (kWe) each. Commissioning of this CHP plant is planned for early 2016.
Future installations at Bushkoppies, Goudkoppies and Olifantsvlei are planned and will follow once the digester capacity at these Works is installed and optimized.