The use of activated carbon in drinking water treatment means that it has to be reactivated on a regular basis, and so this type of treatment has a significant environmental impact. Studying the different types of activated carbon available on the market shows that it is mainly the standing time of the carbon in the treatment process that determines the total impact rather than the raw materials from which the carbon is made.
Environmental impact of filtration with carbon on drinking water treatment
Filtration with activated carbon is an effective approach to drinking water treatment that is widely used. However, it has a relatively large environmental impact (about 5% of the total impact of the purification treatment process) because of the regular reactivation of the carbon. This means that the carbon has to be transported to the supplier, where it is treated at high temperatures, and partly replaced. Above all, this process consumes a lot of energy.
At present, for a variety of reasons (sustainability, availability, cost, properties and also competitiveness), carbon manufacturers supply all kinds of carbon made from different raw materials. This study looked at whether new types of activated carbon of this could help to reduce the environmental impact of water treatment. A Life Cycle Analysis (LCA) was conducted for this purpose.
Three different types of activated carbon
On the basis of literature data, available databases and information from carbon producers, an overview was drawn up of the impact of different types of activated carbon on the environment. The study looked at the use of activated carbon-based on coal, wood and coconut shells with a specific focus on water treatment.
Standing time as a major factor
The environmental impact of activated carbon is mainly attributable to energy consumption during reactivation, which is required regularly. The impact of the reactivation process in itself is similar for all three types of carbon. However, approximately 10-15% of the carbon is lost during this process and it has to be replaced by fresh activated carbon. Obviously, the raw material plays a greater role in the overall environmental impact with fresh carbon than when it is regenerated, and coal-based carbon has most impact. However, this accounts for only 10-15% of the impact of reactivation.
It has emerged that the raw material does have a major effect on the service life of the carbon and therefore on the regeneration frequency. Coconut carbon has to be reactivated more often initially, increasing the impact of this carbon. The best way to reduce the impact of the activated carbon process is to try and extend the standing time of the carbon. Transport and raw materials make only a limited contribution to the environmental impact.