Unlocking the value of wastewater

In the cycle of life, sewage treatment works are pivotal in providing safe sanitation, and in ensuring that treated effluent re-enters the environment for future abstraction.

Alastair Currie speaks to Kennedy Chihota, managing director at ERWAT, about his organisation’s role as the City of Ekurhuleni’s dedicated wastewater treatment company, as well as key action plans that could assist other municipalities nationally.

What’s your field of expertise?

KC I’m a civil engineer by profession with a core interest in water and wastewater. Over the years, I’ve worked on both small- and large-scale projects within the municipal engineering space. These include rural municipalities in Limpopo, the City of Cape Town and Johannesburg Water, prior to joining the City of Ekurhuleni in 2013, where I started off as the divisional head responsible for strategic planning on key infrastructure projects. The latter included the progressive construction of some 40 reservoirs, where the objective was to increase the City’s overall average storage capacity from 24 to 36 hours to improve water supply security.

I was subsequently seconded to ERWAT (Ekurhuleni Water Care Company) in December 2021 to serve as acting MD and was officially appointed in a permanent capacity from 1 October 2022. I’m tremendously excited about the opportunity it presents to take ERWAT to new levels of performance.

Who owns ERWAT?

ERWAT is a municipal-owned entity and the

City of Ekurhuleni is the major shareholder (97%). The remaining shareholders are the City of Johannesburg (1.5%) and Lesedi Local Municipality (1.5%).

As an NPC, our operating mandate is ostensibly limited to the boundaries of the City of Ekurhuleni. This is definitely the case where we perform on-site services for private clients in terms of outsourced operations and maintenance (O&M) contracts. However, we can perform work for any municipality nationally if this is agreed to by a municipal council resolution.

The point to emphasise is that NPCs don’t pay out dividends to shareholders, but they still need to run as going concerns – and that requires money. For this reason, ERWAT has a responsibility to all its stakeholders to ensure it’s as financially self-sufficient. Essentially, we must ensure that sufficient funds are available to optimise the life and performance of our assets.

What’s ERWAT’s vision and operational strategy?

Our vision is to become a globally recognised water resources company – with a major emphasis on the word ‘resources’ because wastewater has a value. In this respect, we’re focusing on two major beneficiating streams: first, reuse – treating effluent to a standard acceptable for industrial applications, like cooling; and second, finding a commercial use for our sludge – the solids wastewater treatment by-product. Current volumes across our plants are around 200 t/day.

At present, we often end up transporting this treated sludge, at our own cost, to farmers, where they use it as a fertiliser – a common practice worldwide. But this is not financially sustainable, so we need to find a solution that makes our sludge a desired and saleable product. This requires investing in specific processes, like hydrolysis, that further improves the quality and commercial value to a broader market.

By ‘cooking’ the sludge through thermal hydrolysis, we can kill the pathogens, but retain the nutrients. The end-product can then be sold in small or bulk bags for domestic and/or industrial application.

An allied option is to use the sludge to produce methane to run gas turbine generators. This type of waste-to-energy concept has already been piloted in Europe and there’s strong interest locally.

Either way, our plan going forward is to investigate a public-private partnership (PPP) concession model for the beneficiation and sale of marketable sludge. Watch this space.

What is the percentage of effluent currently being treated?

Currently, Ekurhuleni buys some 1 000 Mℓ/day of bulk water from Rand Water. Of that, some 15% is consumed, so it doesn’t find its way into the sewer system, but the balance does, equating to a daily effluent inflow of around 850 Mℓ/day. This is a substantial volume to manage and treat to standard before it can be discharged back into the environment through rivers, dams and streams.

Of the 850 Mℓ/day treated, 630 Mℓ/day is what we are required to discharge in terms of ERWAT’s water use license conditions. Remember, there are other downstream users (predominantly municipalities, but also private industry and farmers) who will be abstracting this treated effluent for potable water treatment. So, the cycle must be maintained.

What happens to the surplus effluent?

We see huge opportunity in commercialising the 220 Mℓ treated surplus effluent. We can polish it and sell it to industries that don’t require potable water for their operations. As opposed to buying potable water at, say R12.00/k ℓ , industrial users could potentially buy our treated reused water (not to potable standard) at as low as

Structa Technology’s Prestanks are hygienically safe, cost effective and a reliable way to store water for commercial sectors, private sectors and even for personalized storage. Temporary or permanent erection at mines, powerstations, building sites, hospitals, water affairs,municipalities, rural communities and agriculture.

R2.00/kℓ – a massive saving and a winwin from a sustainability perspective. Plus, ERWAT could raise some money that can be used to fund and upgrade facilities and services.

We’ve completed an off-taker feasibility study as part of preparing the business case. The next stage is to build a dedicated polishing plant, and we intend to advertise for design bid proposals in the coming months. Currently, we sell around 50 Mℓ/day of treated effluent to mines in the area, but we now want to upscale the whole operation.

Are all of ERWAT’s plants running at optimum capacity?

Process efficiencies are on par with local and international standards. The main challenge, however, is the diverse range and size of our 19 water care works (WCWs). For example, ERWAT’s Ester Park WCW facility is a 1 Mℓ plant, while our largest treatment works, Waterval, is designed to process around 174 Mℓ

The extreme variability in plant sizes is due to historical factors, namely the post-1994 integration of various towns as part of the establishment of today’s Ekurhuleni metro footprint. Since these towns were originally planned in isolation from each other, operational consolidation and streaming now needs to take place, which has been identified in the City’s 50-year masterplan. That will entail reducing the number of ERWAT plants to 10 and upscaling five of them, with a panel of external consulting engineers currently working on their redesign. There’s a possibility that two of the five, which includes Waterval, could be run as PPPs. That’s a key factor in bridging any National Treasury funding gaps. Waterval is also a logical site for our proposed new polishing plant.

Just to illustrate the point when it comes to scalability, the City of Johannesburg only has six plants, but they receive almost 15% more daily effluent than ERWAT. Johannesburg’s largest plant – Northern Works – is a modern facility with a capacity of 400 Mℓ. So, we need to follow a similar operating model to maximise efficiencies. Plus, we need to build additional capacity in preparation for future residential and industrial expansion.

Aside from new construction, bestin-class maintenance regimes are essential. The international benchmark is around 5% of turnover on repairs and maintenance annually. In ERWAT’s case, that’s about R400 million, mostly directed at electromechanical systems where the highest availability is critical.

How have the plants performed in terms of the Green Drop programme?

Green Drop certification is a very important initiative by the Department of Water and Sanitation, and ERWAT fully supports the bi-annual audit process.

According to the 2022 Green Drop Report, there are around 950 wastewater treatment plants in South Africa. Of these, only 22 were Green Drop certified following the most recent 2021 assessment. Seven were ERWAT plants. That’s good in terms of ERWAT’s overall performance, but really concerning for the country, with 334 WCWs in critical state.

I want to add that our other 12 plants that didn’t pass the Green Drop audit are far from dysfunctional. The Green Drop process is based on a multicriteria assessment. Examples include capacity management, environmental management, technical management, financial management, effluent and sludge management. ERWAT incurred points deduction due to hydraulic overloads on seven WCWs, compliance in the other three main criteria notwithstanding.

Simply put, if a plant has a designed capacity of 10 Mℓ/day but is receiving 11 Mℓ/day – irrespective of whether the plant is performing to standard in all the other criteria – there’s an immediate 10-point deduction. The Green Drop ‘pass rate’ is 90%. In ERWAT’s case, we have eight plants that are hydraulically overloaded. They came close but didn’t make the cut.

What about load-shedding?

Of course, load-shedding is a factor, which we need to manage for now. In response, we’re progressively installing gensets as backups on critical process stages. Longer term, we need to look at alternative power solutions to minimise interruptions and save costs. Last year, for example, ERWAT’s electricity bill was approximately R157 million.

Our power requirement is around 28 MW to run all our plants and we believe investing in solar PV could meet a key part of this demand, based on a recent study. The anticipated capital outlay is around R800 million, with a payback period of between five to ten years. Since these PV installations can easily last 20 years, that’s a great return on investment, namely 10 years of free electricity.

And in closing?

Delivering world-class wastewater services is ERWAT’s first priority because without effective process performance in this area, no society can function. Since its formation in 1992, ERWAT has led the way in the adoption of new technologies and sustained our operations by investing in the best engineering and technical talent.

The fact that so many municipal treatment works in the country are not running to the required standard is distressing and we believe it’s ERWAT’s responsibility to assist wherever practical, either in terms of expert mentorship and/or O&M services. The seven Green Drop awards achieved by ERWAT testify to that.

Going forward, we need a universally adopted circular economy strategy on wastewater and a clear understanding of the vital imperative of reuse to sustain our environment and society.