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AIM: This study aimed to assess the quality of water and sediment of urban streams (Lajeado, Preto, Pedras and Lewis-Pedroso) located in Santa Cruz do Sul County, RS, Brazil, using the microcrustacean Ceriodaphnia dubia as test-organism. METHODS: Quarterly scientific excursions to the streams were held on August and November 2011, February and May of 2012 in order to collect water and sediment samples, in the upper reaches (P1, P3, P5, P7) and lower reaches (P2, P4, P6, P8), totalizing 8 points. To evaluate the toxicity (acute and chronic), the microcrustacean C. dubia was used. RESULTS AND CONCLUSION: The results indicated high toxicity levels detected in samples P2, P6 and P8 (lower reaches), as they caused the mortality of 100% of organisms in the water samples (P6 and P8) and sediment samples (P2 and P8), denoting acute effect. Yet, all upstream sites showed chronic effects in sediment samples, at least for one collection period, with the highest significant toxicity level among all samples (55.2%), which indicates the presence of contamination even in upper areas. These results indicated a strong degradation of the water and sediment quality of urban streams coming from the wastewater and industrial discharges of the urban area, which can cause damage to the biota as well as the public health, due to the multiples uses of water that the local population does, highlighting many of them as inappropriate to the water quality detected, such as the primary contact recreation (balneability). OBJETIVO: O presente estudo teve como objetivo avaliar a qualidade da água e do sedimento de córregos urbanos (Lajeado, Preto, Pedras e Lewis-Pedroso) localizados no município de Santa Cruz do Sul, RS, Brasil, utilizando o microcrustáceo Ceriodaphnia dubia como organismo-teste. MÉTODOS: Excursões científicas trimestrais foram realizadas nesses arroios, em agosto e novembro de 2011; fevereiro e maio de 2012, para coletar amostras de água e sedimento nos trechos superiores (P2, P4, P6 e P8) e nos trechos inferiores (P1, P3, P5 e P7), totalizando 8 pontos. Para avaliar a toxicidade (aguda e crônica), utilizou-se o microcrustáceo C. dubia. RESULTADOS E CONCLUSÃO: Os resultados indicaram alta toxicidade nos pontos P2, P6 e P8 (trechos inferiores), uma vez que causaram 100% de mortalidade dos organismos nas amostras de água (P6 e P8) e amostras de sedimento (P2 e P8), denotando efeito agudo. Ainda, todos os trechos superiores mostraram efeito crônico em amostras de sedimento, em pelo menos uma época de amostragem, com os maiores níveis de toxicidade significativa entre todas as amostras (55.2%), o que indica a presença de contaminação mesmos em trechos superiores. Estes resultados indicaram uma forte degradação da qualidade da água e do sedimento dos arroios urbanos proveniente das descargas de águas residuais e industriais da área urbana, que podem causar danos à biota, bem como a saúde pública, devido aos múltiplos usos de água que a população local faz, destacando muitos deles como inadequados para a qualidade da água detectada, como a recreação de contato primário (balneabilididade).

This research evaluates the removal of nutrients by microalgae in different photoperiod cycles, combined with constructed wetland in the wastewater treatment plant of the University of Santa Cruz do Sul, RS, Brazil. The treatment used took place between July and December 2018 and consisted of the following steps: preliminary treatment, secondary treatment with an anaerobic reactor, microalgae tank (MT), sand filter and constructed wetland, using the macrophyte Chrysopogon zizanioides. In the microalgae tank, three light cycles were considered: 12h/12h, 24h and 18h/06h, whose lighting was powered by a white LED lamp of 9 Watts and 6000 Kelvin, regulated by a light controller. The results indicated that there were no significant differences (p>0.05) between the values of soluble phosphorus, ammoniacal nitrogen, COD and BOD for MT comparing the three photoperiod cycles (12h/12h, 24h and 18h/06h). However, the system setup removed 100% of total coliforms, E. coli and TSS in the three light cycles. Regarding the removal of nutrients and organic matter, the light cycle with the best performance was the 24-hour cycle, considering a removal of 67.6% for soluble phosphorus, 94.0% for ammoniacal nitrogen, 63.7% for COD and 42, 7% for BOD, at the end of the treatment process. These results demonstrate that the use of microalgae in combination with constructed wetland has greater efficiency in the removal of nutrients, mainly phosphorus and nitrogen, in addition to reducing physical-chemical parameters and eliminating effluent toxicity.  Keywords: light cycles, microalgae tank, wastewater treatment plant.

This analysis applied systematic review as a methodology for identifying, analyzing and interpreting data on the use of water quality indices for human consumption. Scientific articles were searched in the “PubMed”, “Scielo”, “ScienceDirect” and “Web of Science\" databases, using the keywords “drinking water” and “water quality index”, with a custom interval between 2000 and 2020. The results indicated 82,573 published articles, with 16 of them being selected after a filtering process. The occurrence of 11 water quality indices was verified, including 47 water quality parameters used to assess the quality of drinking water, highlighting that the parameters pH, Nitrate, Turbidity, Chloride and Sulfate were the most used, cited in 10 of the 16 articles selected (62,5%). We suggest that future studies seek to propose regionalized water quality indicators for consumption, in order to consider local aspects in the evaluation process and to determine intervention priorities by health surveillance agencies.

This research developed a Water Quality Index (WQI) for public supply in the Vale do Rio Pardo Region, RS, Brazil (WQI-VRP), from the database of the 13th Regional Health Coordination, totaling 1175 samples. A filtration process resulted in 285 samples with the variables free residual chlorine, turbidity, apparent color, pH, fluoride, total coliforms and Escherichia coli. For water consumption purposes, the Water Quality Index developed by the Sanitation Company of Goiás, Brazil, was used. A multivariate calibration of the weights of importance of the parameters included in the original index was performed, resulting in the WQI-VRP. Comparing the medians of the two indexes, it was found that there were significant differences (p<0.05), qualifying the WQI-VRP as more restrictive. The results indicated that 89.8% of the samples were classified as non-compliant samples by WQI-VRP, while 10.2% were classified as compliant samples. Of the 285 samples analyzed, 72 samples of chlorine, 12 of total coliform, 5 of E. coli, 2 of color, 200 of fluoride and 26 of pH, were below or above the minimum or maximum values required by Brazilian legislation. The pH and fluoride correspond to the critical variables of the study region, as they were the parameters that showed the greatest increases in relative weights when comparing the original index with the calibrated one. These results confirm the use of the WQI-VRP as an efficient tool to assess the quality of drinking water in Brazilian subtropical and temperate lotic systems.

The industrial processing of precious stones is a source of revenue for several Brazilian towns, especially in the state of Rio Grande do Sul. Given the growing number of small-sized companies that process precious stones, wastewater production is inevitable and is a cause for concern inasmuch as preservation of nature is considered. The present study investigates the detoxification of the wastewater produced by the process of rhodamine B dyeing using oxidation processes. Ozonization (O 3 ), ultraviolet irradiation (UV), and O 3 /UV methods were assessed. Some of the parameters used to measure the efficiency of the analyzed treatments included COD, ecotoxicity ( Daphnia magna ), cytotoxicity, and genotoxicity assays ( Allium cepa assays). Results show predominance of negative and local environmental impacts, which are reversible in more than 70% of cases. The major proposed reversibility measures were the change in the process layout and dye wastewater segregation. Among the analyzed methods, ozonization proved to be more efficient in decolorization, with 60 min of treatment, pH = 9 and dosage of 5.705 mg O 3 /mg of rhodamine B. A pseudo first-order reaction, with a kinetic constant of 7.5 × 10 −2  min −1 , was observed. The cytotoxic and genotoxic effects were assessed for both raw and treated wastewaters. Despite complete decolorization, cytotoxicity and genotoxicity assays revealed an EC 50 of 28.6, in addition to chromosome aberrations in 40% of dividing cells for the treated wastewater.

This research evaluated the effectiveness of the implementation of water resource preservation areas in the Hydrographical Basin of Andreas Stream, county of Vera Cruz, RS, Brazil, established through Payment for Environmental Services (PES), using an environmental monitoring program to assess physical, chemical and microbiological variables. The PES is linked to the \"Water Guardian\" project, which aims to ensure the preservation of water resources by paying farmers for providing the environmental services to protect the springs and riparian areas that lie within their properties. Twenty sampling stations were selected for collecting water samples monthly during the period July 2012 to June 2014 (460 samples) to evaluate the following variables: water temperature, pH, turbidity, dissolved oxygen, biochemical oxygen demand, nitrate, ammonia nitrogen, phosphate, total dissolved solids and thermotolerant coliforms. The evaluation was made based on decree 357/2005 of the National Environmental Council (CONAMA) and by applying the Water Quality Index (WQI). The results indicated a significant improvement in the water quality when comparisons were made between the periods before and after the installation of the preservation areas. The sampling points classified as “good” (CONAMA and WQI), which indicates water of good quality that is appropriate for multiple uses, increased from 52.0% to 72.0%. In this sense, promoting the preservation of headwaters and riparian zones becomes of fundamental importance and highlights the role of PES as an operational tool for water resource preservation.

The aim of the present study was to assess the ecotoxicity and genotoxicity of hospital laundry wastewaters generated from a regional hospital located in Rio Pardo Valley in the state of Rio Grande do Sul, Brazil. Physicochemical, microbiological, ecotoxicological, and genotoxic analyses were performed, and the results indicate that some parameters were not in accordance with the limit concentrations established by Brazilian and international guidelines for urban wastewaters. Daphnia magna (EC 50 2.01 %) and Danio rerio (LC 50 29.25 %) acute toxicity was detected, and sublethal effects were identified in Lactuca sativa (IC 25 12.50 %) and Allium cepa (IC 25 51.25 %). Cytotoxicity was observed at the five wastewater concentrations used yielding statistically significant differences ( p  < 0.05) in the meristematic cells of A. cepa compared with the negative control. The results obtained here warn about the necessity to develop treatment methods that can mitigate the environmental impacts caused by the ecotoxicity and genotoxicity of hospital laundry wastewaters.

This study aimed to assess the quality of water and sediment of urban streams located in Santa Cruz do Sul County, RS, Brazil, using the microcrustacean Ceriodaphnia dubia as test-organism. Quarterly scientific excursions to the streams were held on August and November 2011, February and May of 2012 in order to collect water and sediment samples, in the upper reaches and lower reaches, totalizing 8 points. To evaluate the toxicity, the microcrustacean C. dubia was used. The results indicated high toxicity levels detected in samples P2, P6 and P8, as they caused the mortality of 100% of organisms in the water samples and sediment samples, denoting acute effect. Yet, all upstream sites showed chronic effects in sediment samples, at least for one collection period, with the highest significant toxicity level among all samples, which indicates the presence of contamination even in upper areas.

This research evaluates the removal of nutrients by microalgae in different photoperiod cycles, combined with constructed wetland in the wastewater treatment plant of the University of Santa Cruz do Sul, RS, Brazil. The treatment used took place between July and December 2018 and consisted of the following steps: preliminary treatment, secondary treatment with an anaerobic reactor, microalgae tank (MT), sand filter and constructed wetland, using the macrophyte Chrysopogon zizanioides. In the microalgae tank, three light cycles were considered: 12h/12h, 24h and 18h/06h, whose lighting was powered by a white LED lamp of 9 Watts and 6000 Kelvin, regulated by a light controller. The results indicated that there were no significant differences (p>0.05) between the values of soluble phosphorus, ammoniacal nitrogen, COD and BOD for MT comparing the three photoperiod cycles (12h/12h, 24h and 18h/06h). However, the system setup removed 100% of total coliforms, E. coli and TSS in the three light cycles. Regarding the removal of nutrients and organic matter, the light cycle with the best performance was the 24-hour cycle, considering a removal of 67.6% for soluble phosphorus, 94.0% for ammoniacal nitrogen, 63.7% for COD and 42, 7% for BOD, at the end of the treatment process. These results demonstrate that the use of microalgae in combination with constructed wetland has greater efficiency in the removal of nutrients, mainly phosphorus and nitrogen, in addition to reducing physical-chemical parameters and eliminating effluent toxicity.  Keywords: light cycles, microalgae tank, wastewater treatment plant.

Water contamination by discharge of untreated or poorly treated wastewater into water bodies is a current issue that may cause harm to humans. Water quality assessment targets general parameters, which often misleads to underestimation of their implication in the environment. Acute and genotoxicity assays using Daphnia magna is a reliable tool for testing deleterious effects of wastewater exposure. This paper aimed at evaluating acute ecotoxicity as well as genotoxicity of a biological treatment system composed by an anaerobic bioreactor (AR), algal turf scrubber (ATS), followed by two downflow constructed wetlands (CW). The university’s wastewater treatment plant (WWTP) composed by an equalization tank (ET), an upflow anaerobic sludge blanket (UASB), followed by an aerobic bioreactor (AB) was also assessed for acute and genotoxicity. Our results showed the acute ecotoxicity ranged from moderately to extremely toxic, and from nontoxic to moderately toxic for ET and AB. For AR, most samples were moderately toxic. The outflow from ATS and CW’s tanks completely eliminated acute toxicity and genotoxicity evidencing that the proposed system combining ATS and vertical CWs is suitable for treating sanitary wastewater.