Sistema combinado de reatores anaeróbios com Wetlands construídos + ozonização para o tratamento e reuso de águas residuárias.

Abstract

In Brazil, rural sanitation is nowadays one of the main challenges for the universal access to basic sanitation, primarily the collection and treatment of domestic wastewater, which still present lack of investments. This aspect, combined with the environmental crisis faced by today's society, are promoting the search for decentralized wastewater treatment technologies, with low costs and more environmentally sustainable. In this context, Constructed Wetlands (CWs) present an interesting technology with simple operation and that can promote the recycling of nutrients and water reuse. The present study's objective was to develop a combined system in batch flow and semi-pilot scale for treatment and reuse of wastewater, composed by anaerobic reactors (AR), Constructed Wetlands (CW), and lately ozonation,. The ARs consisted of 4 containers of HDPE and of 100 L each (1 sedimentation tank and 3bioreactors), fed with the campus of University of Santa Cruz (UNISC) wastewater, and with a HRT of 7 days. After the ARs, the wastewater was sent to the CWs, which were composed by 2 boxes of HDPE (W1 and W3), with 200 L each, and one fiber box (W2) with a 100 L volume. The first box (W1) had a floating macrophyte filter built with expanded polyethylene, as well as the second one (W2), but the W2 also had alternate flow (baffled) caused by vertical chicanes. The third and last CW (W3), was built using rocks (15 cm) and gravel n. 2 and n. 3 (25 cm). The CW were vegetated with different combinations of the H. grumosa, P. Stratiotes, Spirodela and Salvinia macrhophytes.. The HRT of each CW was 7 days, and the pollutant loading rates were observed and compared to literature recommendations. During the last 3 months, the ozonation process was applied to the treated samples in a 1,4 L reactor, for 1 hour and by bubbling with 240 mg O3 h-1. The developed combined system was monitored for 10 months, in which several parameters related to the wastewater emission and water reuse standards were analysed, before and after each stage of treatment. From the obtained results, it was possible to verify that the system was efficient at nutrients removal (mostly the W3 for N and P), and as well for organic matter, color and turbidity (although the ARs and W1 were the most efficient). In addition, the system also demonstrated great result for removing pathogenic organisms acute toxicity, transforming the wastewater from moderately toxic to absence of toxicity. The ozonation, on the other hand, resulted mostly in color removal and pH increase. The average month results for each parameter were compared to and stayed below the Brazilian emissions standards of CONSEMA 355/2017 and the effluent could be classified as water class 2 for reuse according to the NBR 13969/97.