Avaliação do Ciclo de Vida de sistemas de tratamento de efluentes urbanos utilizando Microalgas e Wetlands Construídos

Developing wastewater sanitation in a decentralized way makes it possible to study the shortage of almost 50% of Brazilian municipalities. Thus, the main purpose of this study was the use of the Life Cycle Assessment for the application of the integrated systems of anaerobic reactor, Wetlands Constructed (WCs) of vertical/horizontal flow and Microalgas (MA). The functional unit was defined as 1,200 m3 of effluent treated for 20 years, and the boundary of the system was delimited by the entry of the raw sewage into the UASB reactor until the departure of the final effluent treated to the receiving body. The ACV study used the SimaPro® 8.04 program and the Impact 2002+ method. For the categories of impact in the construction and operation stages were applied the Normalization, Characterization, Weighting and Network Inventory of the obtained data. Through it was possible to identify the main items for the sustainable environmental development of these systems, with the highest impacts in the construction phase (92.3%) related to the use of high density polyethylene (32.8%), sand (27.2%) and polyvinyl chloride (18.8%). Already in the operation phase the greatest impact was the use of electricity in the Microalgas Pre-Wetlands system due to the dependence of non-renewable resources.Desenvolver o saneamento de águas residuárias de forma descentralizada significa pesquisar a carência de quase 50% dos municípios brasileiros. Neste sentido a principal finalidade deste estudo foi o uso da Avaliação do Ciclo de Vida para aplicação dos sistemas integrados de reator anaeróbio, Wetlands Construídos (WCs) de fluxo vertical/horizontal e Microalgas (MA). A unidade funcional foi definida como 1.200 m3 de efluente tratado durante 20 anos e a fronteira do sistema foi delimitada pela entrada do esgoto bruto no reator UASB até a partida do efluente final tratado para o corpo receptor. O estudo de ACV utilizou o programa SimaPro® 8.04 e o método Impact 2002+. Para as categorias de impacto nas etapas de construção e operação foram aplicados a Normalização, Caracterização, Ponderação e Inventário de Rede dos dados obtidos. Desta forma foi possível a identificação dos principais itens para o desenvolvimento ambiental sustentável destes sistemas, sendo que foram identificados os maiores impactos na fase de construção (92,3%) relacionados a utilização de polietileno de alta densidade (32,8%), areia (27,2%) e policloreto de vinila (18,8%). Já na fase de operação o maior impacto foi a utilização de energia elétrica no sistema Microalgas Pré-Wetlands devido a dependência de recursos não renováveis

Floating treatment wetlands in domestic wastewater treatment as a decentralized sanitation alternative

Floating treatment wetlands (FTW) are technologies that have stood out for their efficiency, ease of installation and maintenance. They consist of macrophytes emerging in a floating structure that keep the plant roots in direct contact with the effluent regardless of the water flow variation over time, allowing the removal of pollutants by various processes. The application of FTWs for the treatment of domestic wastewater has the advantage of low costs in terms of removing nutrients and at the same time reducing the cost of maintenance and energy consumption when compared to the conventional centralized treatment of effluent. The lack of wastewater treatment in areas distant from urban centers is even more limited, mainly due to the high cost of tubing and pumps for the effluent to reach the treatment plants. Therefore, the objective of this study was to research FTW systems applied to the decentralized treatment of domestic wastewater. First, a bibliometric analysis was conducted comparing the main issues involving FTW, and the challenges regarding the integration of FTW and domestic wastewater treatment systems. The feasibility of the floating system as a decentralized treatment approach were discussed, as well as the removal of nutrients in domestic wastewater, which was the most covered topic by researchers who developed studies in the area. In addition, other technologies are being integrated into the phytoremediation systems seeking to improve the quality of the treated effluent and assessing the potential reuse in the homes where they are generated and treated, determining the costs and space requirements for the entire process. There is a large research gap regarding the treatment of domestic wastewater by FTW in decentralized systems, mainly in terms of operation, cost assessment and reuse Therefore, further investigations in order to better understand the performance of the process and the reactions that occur with physical, chemical and microbiological removal mechanisms are still necessary

Hybrid constructed wetlands integrated with microbial fuel cells and reactive bed filter for wastewater treatment and bioelectricity generation

The present study aimed to develop a pilot-scale integrated system composed of anaerobic biofilter (AF), a floating treatment wetland (FTW) unit, and a vertical flow constructed wetland coupled with a microbial fuel cell (CW-MFC) and a reactive bed filter (RBF) for simultaneously decentralized urban wastewater treatment and bioelectricity generation. The first treatment stage (AF) had 1450 L and two compartments: a settler and a second one filled with plastic conduits. The two CWs (1000 L each) were vegetated with mixed plant species, the first supported in a buoyant expanded polyethylene foam and the second (CW-MFC) filled with pebbles and gravel, whereas the RBF unit was filled with P adsorbent material (light expanded clay aggregate, or LECA) and sand. In the CW-MFC units, 4 pairs of electrode chambers were placed in different spacing. First, both cathode and anode electrodes were composed of graphite sticks and monitored as open circuit. Later, the cathode electrodes were replaced by granular activated carbon (GAC) and monitored as open and closed circuits. The combined system efficiently reduced COD (> 64.65%), BOD₅(81.95%), N-NH₃(93.17%), TP (86.93%), turbidity (94.3%), and total coliforms (removal of three log units). Concerning bioenergy, highest voltage values were obtained with GAC electrodes, reaching up to 557 mV (open circuit) and considerably lower voltage outputs with closed circuit (23.1 mV). Maximum power densities were obtained with 20 cm (0.325 mW/m²) and 30 cm (0.251 mW/m2). Besides the electrode superficial areas, the HRT and the water level may have influenced the voltage values, impacting DO and COD concentrations in the wastewater