Constructed Wetlands Integrated with Advanced Oxidation Processes in Wastewater Treatment for Reuse

New low-cost biofilters for SARS-CoV-2 using Hymenachne grumosa as a precursor

The ongoing global spread of COVID-19 (SARS-CoV-2 2019 disease) is causing an unprecedented repercussion on human health and the economy. Despite the primary mode of transmission being through air droplets and contact, the transmission via wastewater is a critical concern. There is a lack of techniques able to provide complete disinfection, along with the uncertainty related to the behavior of SARS-CoV-2 in the natural environment and risks of contamination. This fact makes urgent the research towards new alternatives for virus removal from water and wastewater. Thus, this research aimed to characterize new lost-cost adsorbents for SARS-CoV-2 using Hymenachne grumosa as a precursor and verify its potential for removing SARS-CoV-2 from the solution. The aquatic macrophyte H. grumosa had in natura and activated carbon produced with H. grumosa and zinc chloride (ZnCl_2,1:1) impregnation and carbonization (700 °C, 1 h) were incubated for 24 h with inactivated SARS-CoV-2 viral suspension, and then the ribonucleic acid (RNA) was extracted and viral load quantified through reverse transcription-quantitative polymerase chain reaction (RT-qPCR) technique. The results demonstrated the great adsorption potential, achieving removal of 98.44% by H. grumosa "in natura", and 99.61% by H. grumosa with carbon activation, being similar to commercial activated carbon (99.67%). Thus, this study highlights the possibility of low-cost biofilters to be used for SARS-CoV-2 removal, as an excellent alternative for wastewater treatment or watercourses decontamination.

Biomonitoring of urban wastewaters treated by an integrated system combining microalgae and constructed wetlands

The objectives of the present study were to apply different, toxicological assays for monitoring the toxicity of treated and untreated urban effluents produced at a university campus. The research was conducted at the wastewater treatment plant of the University of Santa Cruz do Sul, (UNISC), from october 2018 to april 2019. An integrated system with, anaerobic reactor (AR), microalgae (MA) and constructed wetlands (CWs) was, proposed for detoxification of the wastewaters produced at the university campus with a hydraulic detention time of 17 days. Daphnia, magna (ecotoxicity) and Allium cepa (phytotoxicity, cytotoxicity, and, genotoxicity) were used as tools to monitor the efficiency of the integrated system. Obtained results showed that the integrated system (MA, + CWs) presented good COD and BOD5 reductions, besides removal rates of, almost 98% for N-NH3, being much more efficient than the UNISC wastewater, treatment plant (UWTTP). The results of ecotoxicity presented the raw wastewaters (RW) as slightly toxic and an absence of ecotoxicity in all the treatments steps. Regarding phytotoxicity, the results showed no significant differences between the treatments. The cytogenetic assays indicated a significant increase in mitotic index (MI) (p < 0.001) after treatment by CWs compared to the final treatment UWTTP while the results, regarding binucleated cells (BNC) did not present significant differences, among the treatments. Micronucleus (MN) indexes were significantly different between the UWWPT and the integrated system (p < 0.01). In relation to chromosome aberrations (CA) the results indicate a significant difference between the CWs and UWWTP treatments (p < 0.01) and, RW and CWs (p < 0.001), confirming the detoxifying potential of the integrated system when compared to UWWPT. Thus, the results of the present research highlight the relevance in the proposition of the integrated system as an alternative of cleaner technology to the detriment of conventional technologies applied in wastewater treatment.

Algae turf scrubber and vertical constructed wetlands combined system for decentralized secondary wastewater treatment

Water shortage is a current problem faced by many regions. The deterioration of water bodies driven by the directly discard of untreated wastewater worsens the water shortage and implies in more costly treatments to meet local standards for water quality. In rural areas, the problem is even worse, once conventional centralized treatment plants do not encompass them. Decentralized treatment systems must present low-cost, local availability, standards-meeting efficiency, and simplified operation. The present study examines the combined use of algae turf scrubber and down-flow vertical constructed wetlands for a University's sanitary wastewater treatment. After a hydraulic detention time of 21 days, the unit was able to reach 49%, 48%, 98%, 82%, 99.2%, 70.1%, 44%, 83%, 72%, 86%, 69%, 95%, and 99.9% for conductivity, total soluble solids, turbidity, apparent color, N-NH₃, total nitrogen, P-soluble, total carbon, chemical oxygen demand, inorganic carbon, TOC, Escherichia coli, and total coliforms. In accord to the Brazilian standard ABNT 13969/97, the treated effluent is eligible for reuse in floor and sidewalks washing, garden irrigation, and landscaping purposes.