Activated carbon (AC) is an effective adsorbent in water treatment but its production method has significant emissions to the environment. This study aims to quantify the environmental impacts of various AC types and determine whether raw material selection could reduce the footprint of AC. A cradle-to-gate life cycle assessment (LCA) was conducted on coal, coconut shell, wood, peat, and reactivated coal ACs. The different types of raw materials were selected to reflect typical global and local availability in the selected location. Life cycle data was collected from the Ecoinvent database, scientific literature, and an industrial producer. Using CML 2001 as a characterization method, potential environmental impacts were calculated for 12 categories. The direct emissions of AC production and electricity production were the largest contributors to environmental impacts. Coal AC had the highest impact in ten out of the twelve categories. On the other hand, reactivated coal and coconut AC had the lowest impacts in three and five categories, respectively. The comparison in carbon footprints between the AC types were found to be dependent on inclusion or exclusion of biogenic emissions: When including biogenic carbon emissions, the Global Warming Potential (GWP) of reactivated coal AC was 72-80% lower than for the virgin ACs. When biogenic carbon emissions were excluded, the GWPs of the residual biomass ACs (coconut shell and wood) were found to be about 50% lower than that of reactivated coal AC. The results demonstrate that raw material choice and production method significantly affect the environmental impact of AC. To minimize site-specific impacts of AC application, technical feasibility of AC and use phase emissions need to be assessed.

Low-pressure membranes (including microfiltration and ultrafiltration) for natural organic matter removal in drinking water treatment have gained increasing interest in the Nordic countries. Microfiltration can produce stable water quality and requires less space than conventional treatment. Hollow fibre microfiltration coupled with chemical coagulation was tested at a Finnish surface water treatment plant to study its feasibility and environmental impact compared to clarification, rapid sand filtration and ozonation. Microfiltration improved both physical and chemical water quality, while natural organic matter removal was similar to that of conventional treatment. Membrane treatment would increase operational costs by 2.5–3.5 euro cents per m³. Most of the costs derive from chemicals used in membrane cleaning. Membrane treatment is an energy-intensive process, but energy production in the Nordic countries has a low emission factor. Greenhouse gas emissions from operating microfiltration are estimated at 16 g CO₂-eq./m³ of permeate. Lowering chemical consumption and using renewable energy in production could decrease total emissions.