🌊 What are the results of using Powdered Activated Carbon (PAC) and Granular Activated Carbon (GAC) to remove micropollutants in full-scale W...
Published on by Hossein Ataei Far, Deputy Manager of the Research, Technology Development, and Industry Relations Center at NWWEC
📈 The PAC has been used at over 20 WWTPs in Germany and Switzerland to extensively remove micropollutants.
🔎PAC is mainly used as a post-treatment by dosing it in tanks that treat the WWTP effluent.
🔎New initiatives are testing integrating PAC into existing WWTP processes, like dosing it into the activated sludge system. A study at the Papendrecht WWTPs showed this doubled micropollutant removal and halved effluent ecotoxicity.
🔎This can be done in special tanks after the existing treatment process (so-called post-treatment through PAC adsorption), but also by dosing powdered carbon directly into the activated sludge tanks (PACAS).
🔎A variant of the 1-STEP filter is the O3-STEP filter in which the 1-STEP filter is combined with ozone dosing. The working life of the activated carbon can then be much longer.
🔎Research aims to improve the effectiveness and efficiency of PAC use at WWTPs, including finding better dosing methods & and locations in the treatment process.
🔎Effects on effluent quality, WWTP operation, and sludge processing are also examined [1].
📈Granular activated carbon (GAC) works similarly to powdered activated carbon but also allows bacteria growth to remove nutrients like nitrogen and phosphate.
🔎A full-scale GAC filter at the Horstermeer WWTP in the Netherlands removes both micropollutants and nutrients. However, micropollutant removal decreases considerably after just 3 months.
🔎GAC is more expensive than PAC. It is not widely used in Germany and Switzerland due to the higher costs. The risks of unknown transformation products or carbon discharge are also unknown.
🔎New technologies are emerging that can improve GAC efficiency, but they are not yet widely used in Germany and Switzerland due to higher costs.
🔎Potential risks exist with GAC like the formation of unknown transformation products and the release of carbon particles. More research is needed to increase GAC effectiveness [1].
📈Super-fine powdered activated carbon (SPAC) is better than regular-sized
powdered activated carbon (PAC) for removing micropollutants from wastewater. In the tested effluent wastewater (5 mg/L DOC), a dose of 13-15 mg/L was necessary to achieve an 80% average removal of indicator micropollutants [2].
📈Activated carbon used currently is mostly from fossil sources like coal. This has a high CO2 footprint.
🔎Initiatives to develop "sustainable carbon" with a lower CO2 footprint are limited so far [1].
Reference:
[1]. Dutch Ministry of Infrastructure and Water Management and STOWA, (2021).
[2]. Bonvin, F., and et al. (2016).
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