Activated Carbon in Wastewater Treatment – An Expensive Mistake?
Activated carbon is considered an effective means of removing micropollutants from wastewater, but appearances are deceptive. In this interview, Dr Reinhard Voigt sheds light on the ecological and economic downsides of this method and shows what sustainable alternatives are available for wastewater treatment.
Activated carbon is often proposed as a solution for removing micropollutants from wastewater. Why do you see this approach as problematic?
Dr. Reinhard Voigt: Activated carbon may initially seem like an effective method to remove micropollutants from wastewater. However, when we examine the environmental and economic impacts, it becomes clear that large-scale use brings significant disadvantages. Producing activated carbon requires enormous amounts of raw materials and energy. The resource consumption is staggering, as large quantities of coal or biomass like wood or coconut shells are needed. Additionally, the costs for disposing of the used activated carbon are high, as it typically must be incinerated. With the phase-out of coal-fired power, finding suitable incineration facilities is becoming increasingly difficult. All of this shows that using activated carbon is neither sustainable nor viable in the long term.
Can you elaborate on the scale of resource consumption and its impact on the CO₂ balance?
Dr. Reinhard Voigt: Let’s take the ZeroTrace project as an example: To achieve an average reduction of 80% in micropollutants, about 30 to 40 grams of powdered activated carbon (PAC) per cubic meter of wastewater are required. When scaled to large treatment plants, this results in an annual demand of around 94,000 tons of activated carbon in Germany alone. The mentioned 94,000 tons of activated carbon are necessary if all wastewater treatment plants of size classes 5 and 4 in Germany were equipped with activated carbon for the fourth treatment stage.
To produce this, about 280,000 tons of hard coal must be processed. Alternatively, it would require 15 times the amount of wood or coconut shells, which is equally unsustainable. The energy needed to activate the carbon is around 85 gigajoules per ton, leading to an additional consumption of 266,000 tons of hard coal per year. In total, we’re talking about 546,000 tons of hard coal annually—a staggering amount. The CO₂ emissions are equally alarming: the production of activated carbon alone generates about 171,000 tons of CO₂ per year. And this doesn’t even account for transportation and disposal costs. These figures highlight the significant environmental footprint of using activated carbon.
Are there alternatives to activated carbon that are more sustainable both environmentally and economically?
Dr. Reinhard Voigt: Yes, there are promising approaches currently being researched. One example is the use of enzymatic reactions in cascaded membrane systems. Unlike activated carbon, which merely binds micropollutants, these processes aim to break down the pollutants directly. This not only reduces raw material and energy consumption but also eliminates the disposal problem associated with used activated carbon. While research in this area is still in its early stages, initial results are promising. Such technologies could offer a more resource-efficient and effective alternative. It’s important that we don’t rely solely on existing, seemingly effective solutions but instead invest in innovative and sustainable methods. In the long run, this would not only benefit the environment but also reduce operational costs for wastewater treatment plants.
Dr. Reinhard Voigt
Head of R&D
Phone: +49 3621 73 77 922
Email: r.voigt@wta-unisol.com
