IWA Publishing

IWA Publishing

Water recycling project - Durban South Africa

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Courtesy of IWA Publishing

1. Overview and key points

South Africa’s first private water recycling project, operating on a 20 year Buy-Operate-Transfer (BOT) basis has turned out to be a success. Constructed in order to treat Durban’s wastewater, it provides a good example of Public Private Partnership (PPP), where appropriate wastewater treatment technology was used in order to provide effluent of a particular standard for industries. This enabled potable water to be freed and directed towards previously unserviced households and at the same time allowed for key industries to reduce their costs by purchasing reclaimed water rather than previously supplied drinking water.

2. Background

Durban is part of the eThekweni Municipality, located on the east coast of South Africa. The combination of limited water resources in the city along with sewage capacity constraints, lead to the investigation of different wastewater recycling processes since the region was producing 450million litres of wastewater a day.

3. Project planning and design

Based on the scarcity of water, the Council’s eThekwini Water Services (EWS) researched the viability of the recycling of treated wastewater. Following laboratory and pilot scale tests on the development of a reclamation process for the production of high quality reclaimed water, it was decided that this was a possible alternative to tackle the water scarcity existing in the area. The construction of a secondary waste water treatment plant and a recycling plant was aimed therefore, at treating wastewater and supplying the treated effluent to a standard, acceptable to industry. It was decided that Mondi Paper located adjacent to the Southern Wastewater Treatment Works (SWTW), having approached EWS previously, be the main customer for this reclaimed water, alogn with Sapref’s fuel refinery as a second client. The aim was to treat 47.5million litres of domestic and industrial wastewater (approximately 10% of the city’s wastewater) to a standard near to potable for sale to these industrial customers for use in their processes.

4. Technology option

In order to provide this service, the existing activated sludge process was upgraded from 50 to 77ml/day, a new tertiary plant was built, the SWTW high level storage tank was refurbished and finally the reclaimed water reticulation system was installed.

For the activated sludge process, a conventional design was used removing 95% of the incoming calculated oxygen demand (COD) and 98% of incoming ammonia loads. The tertiary plant on the other hand focused on the removal of iron through lamella settlers. Lastly, dual media filtration was used to remove the iron precipitate as well as ozonation in order to break down the remaining non-biodegradable organic compound

5. Institutional and management arrangements

EWS recommended to the Council that it would be in their best interest to engage in a PPP, considering the costs, technical complexity and risks associated with the project. Thereafter, following a formal tender process, Durban Water Recyling (Pty) Ltd, was awarded a 20-year concession contract for the production of high quality reclaimed water. Technology and processes are managed by Veolia Water Services (VWS), who make sure that the installations are highly specialised and tailored specifically to meet the water quality requirements of Durban Water Recycling’s primary clients. Preliminary and primary wastewater treatment processes were performed by EWS, whilst the effluent from the primary settlement tank which is fed into the activated sludge planoperated by VWS. At the end of the contracted 20 year period, the facilities would be handed over to the Municipality.

6. Financing arrangements

The capital investment was financed by the Development Bank of Southern Africa (DBSA), Rand Merchant Bank, Societe General and Natexis (two French banks). These investors made sure all initial costs were covered. Where upgrading, new technology investments as well as the risks involved with meeting specific water quality criteria are concerned, this is covered by VWS under their BOT concession. In addition to this, the company pays the municipality for wastewater as well as renting the land where construction has taken place. With 51% of shareholding, VWS is the main stakeholder in this project.

In exchange for the service, the only two clients who make use of this reclaimed pay a standard price/m3 for water.

7. Project outcomes and impacts

At operational capacity the reclamation plant was said to meet 7% of the city’s current potable water demand and at the same time reduce the city’s treated wastewater output by 10%, minimising the wastewater load discharged into the marine environment. Moreover, the volume of potable water saved increased since industrial needs in this case were being satisfied with recycled wastewater.

The provision of reclaimed water to industry proved to be beneficial to these companies, since the tariff paid for this service was much lower when compared to the regular tariff paid for potable water. Two of the main customers were Mondi Paper Mill as well as the Sapref Refinery, owned by Shell and BP.

In addition to this, the technology used was designed specifically for the clients in question and thus the recycled water met the specifications required in order to provide paper of an appropriate quality in the case of Mondi Paper.

8. Overall sustainability of system

Since a substantial amount of water is now being recycled, and used in industry, the demand for potable water for this sector has consequently been reduced. Thus, a larger quantity of drinking water has been freed to provide drinking water to previously unserviced households. At the same time, the treatment of wastewater means that lesser effluent is being discharged, reducing the negative impact on the environment. In addition to this, no new piping was installed, instead the existing facilities were simply upgraded.

For industries this is a viable option since their investment towards this service is a lot lower than it was when engaging in their operations with potable water, thus making it more profitable for them.

Moreover, the technology used was designed so as to work well in combination in order to satisfy the needs of these industries. Although individually each of the technological components used to treat wastewater were standard in the water technology industry, when put together, a highly specialized process was created which was of prime importance to the clients.

Lastly, since the contract was signed on a BOT basis, once the technology and service is returned to the city in 2021, the management and operation skills will be retained since the operations are run mainly by skilled local labour and thus the service can function independently of foreign aid.

9. Lessons learned / Recommendations

Commitment towards purchase of end-product.

Mondi Paper committed its entire paper production to recycled water. This gave the project a high assurance since the end product had a secured client. It also worked for the industries as well since an attractive tariff was offered thus making the initiative profitable.

Wastewater seen as a resource for industry

A profitable use was found for a product which would in the past be discharged into the environment, contributing to pollution. This new perspective seems to have been advantageous not only to the community who enjoys a greater supply of drinking water, but to the reclaimed water clients, who are able to satisfy their production requirements with the treated wastewater for a lower price.

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