Vertical-flow constructed wetlands as a sustainable on-site greywater treatment process for the decrease of micropollutant concentration in urban wastewater and integration to households' water services.

Micropollutant removal from effluent of conventional wastewater treatment has recently become one of the most discussed topics in the design and operation of wastewater treatment plants (WWTPs). This is due to the need to add a post-treatment step to the conventional processes to comply with stricter quality standards for effluents as outlined in the revised Urban Wastewater Treatment Directive (UWWTD). The adoption of on-site or decentralized greywater (GW) treatment in sustainable buildings using vertical-flow constructed wetlands (VFCWs) is a promising direction. It represents an interesting alternative for the removal of micropollutants at the source of pollution, such as personal care products (PCPs) and some pharmaceuticals which are mainly present in this wastewater fraction. Additionally, the treated greywater could be used in households' water services which do not require potable water quality, thus saving drinking water. In this context, this work compares the results of micropollutant removal from projects using VFCWs as a polishing step of WWTPs effluent, as a centralized solution, to the results from a decentralized GW treatment. The results show that VFCWs can remove the investigated micropollutants (Diclofenac and DEET) with an efficiency of >90 %, in both centralized and decentralized treatments. The admixture biochar from plant residues and from cellulose-toilet paper proved to be a promising substitute for the mineral zeolite when mixed with sand to remove PCPs from GW and, therefore, a circular economy concept can be applied to this technology.

Operation of a pilot-scale lipid accumulation technology employing parameters to select Microthrix parvicella for biodiesel production from wastewater.

Wastewater treatment plants (WWTPs) may play a crucial role in shifting to a zero-emission future by becoming more sustainable and contributing to the circular economy (CE). Recovered lipids from urban sewage can serve as a raw material for biofuel production contributing to a waste reduction, mitigation of natural resources depletion and reinforcing security and energy independence. A novel, pilot-scale lipid accumulation technology (LAT) employing parameters to select M. parvicella for the biofuel/biodiesel production was implemented on a side stream of an urban WWTP. The LAT proved its concept as the average amount of extracted lipids accumulated in the bioreactors was three-fold higher when compared to the lipids existing in activated sludge. The average transesterification of extracted lipids to biodiesel resulted in a 1.6 % yield, meaning that from 1 kg of dried sludge, 16 g of biodiesel could be formed. The biodiesel produced complies with European standard specifications (EN14214).