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- Review of dry and wet decentralized sanitation technologies for rural areas: applicability, challenges and opportunitiesPublication . Lourenço, Nelson; Nunes, L.This paper reviews decentralized sanitation technologies comparing dry and wet solutions currently available, discussing their operational requirements, applicability, effluent output quality, efficiencies, environmental impacts, costs, challenges, as well as their advantages and implementation difficulties. Sanitation technologies vary from conventional centralized systems, typically used on urban areas, to decentralized systems, more common in sparse dwellings and small communities of rural areas. Compared with centralized sanitation, decentralized sanitation is being progressively considered as more sustainable solution. Most do not require energy or expensive or sophisticated operation, being easy to adapt to different geographic contexts. A general lack of consistent regulatory control over most dry rudimentary systems and primary treatment systems may compromise water quality and human health. In the future, a mix of new policies and accurate accounting of the location, performance, and degree of failure of such systems should be performed. However, forcing users and communities to face the capital, operational, or repairing costs may be challenging. Since many of the discussed technologies may be important sources of contamination with nutrients, pathogens and toxic chemicals, new opportunities are still open, which include the conversion of dry rudimentary systems into dry controlled systems.
- Life-cycle assessment of decentralized solutions for wastewater treatment in small communitiesPublication . Lourenço, Nelson; Nunes, L.This study benchmarks vermifiltration (VF) as secondary wastewater treatment in three natured-based decentralized treatment plants using life-cycle assessment. The comparison is justified by the comparatively easier and cheaper operation of VF when compared to more traditional technologies, including small rate infiltration (SRI), constructed wetlands (CW), and activated sludge (AS). Standard life cycle assessment was used and applied to three case-studies located in southern Europe. Material intensity during construction was highest for VF, but impacts during operation were lower, compensating those of the other phases. Impacts during the construction phase far outweigh those of operation and dismantling for facilities using constructed wetlands and activated sludge, when the number of served inhabitants is small, and due to lack of economies of scale. VF used as secondary treatment showed to contribute to reduce the environmental impacts, mainly in constructed wetlands and activated sludge. The replacement of CW by VF seems to bring important environmental benefits in most impact categories, in particular in the construction phase. The replacement by VF in facilities with SRI seems to result in the improvement of some of the impact categories, in particular in the operation phase. As for dismantling, no conclusive results were obtained.
- Optimization of a vermifiltration process for treating urban wastewaterPublication . Lourenço, Nelson; Nunes, L.Optimization of a vermifiltration process was made for hydraulic retention time (HRT), hydraulic loading rate (HLR) and recirculation ratio (R), organic loading rate (OLR), earthworm abundance and reactor type on organic matter removal from urban wastewater using a small-scale vermifiltration process comprising single stage, and four-stage vermifilter (VF) systems. All reactor modules were made of PVC with a total volume of 25 L using vermicompost as the filtering material and quartz sand and gravel as the inert filter. System performance was assessed by the removal efficiencies of BOD5, tCOD, sCOD, pCOD, TSS and NH4+. In the earthworm study, four abundances were evaluated: 10 g L-1 (W10), 20 g L-1 (W20), 30 g L-1 (W30) and 40 g L-1 (W40). In the four-stage VF the earthworm abundance evaluated was 20 g L-1. W20 proved to be the optimal treatment condition with efficiencies for BOD5, tCOD, pCOD, TSS and NH4+ of 97.5%, 74.3%, 91.1%, 98.2% and 88.1%, for a pCOD/tCOD ratio of 0.20. The four-stage sequential VF promoted a decrease of BOD5 (98.5%), tCOD (74.3%), pCOD (86.7%), TSS (96.6%), and NH4+ (99.1%). Results indicate that sequential VF systems can significantly improve treatment efficiencies when compared to single stage VF. (C) 2016 Elsevier B.V. All rights reserved.