A new decentralized biological treatment process based on activated carbon targeting organic micropollutant removal from hospital wastewaters

Although hospital wastewaters (HWWs) are usually discharged in urban sewage systems, their separate treatment has several benefits, such as the specific treatment of potential toxics as well as avoidance of further dilutions. In this work, an integrated industrial pilot plant (2200 L) corresponding to the technology SeMPAC(R) is proposed and validated for such purpose. The process consists of a sequential batch reactor (SBR) connected to an external submerged microfiltration membrane, in which powdered activated carbon (PAC) is directly added into the biological reactor to enhance the removal of the organic micropollutants (OMPs). The combination of different redox conditions in the SBR, as well as the operation at long sludge retention times (SRTs) and high biomass concentrations favored OMP biotransformation in the SBR, being their final removal efficiencies enhanced clearly after PAC addition, especially for the recalcitrant compounds. A periodical renewal of the adsorbent is necessary to overcome its gradual saturation. The main operational conditions were influenced by (i) the recalcitrant OMP carbamazepine, which defines the PAC dosage; (ii) the easily degradable OMP ibuprofen, which can be used to optimize the duration of the aerobic cycle; and (iii) the denitrification efficiency, which defines the correct time length of the anoxic period.