Rafael Kopschitz Xavier Bastos

Tratamento de esgotos sanitários em sistemas reatores UASB/wetlands construídas de fluxo horizontal: eficiência e estabilidade de remoção de matéria orgânica, sólidos, nutrientes e coliformes

This work presented the results of a 19-month study on the performance of constructed wetlands in terms of organic matter, solids, nutrients and coliforms removal in pilot scale unities with horizontal, subsurface and surface flow, with hydraulic retention time from 1.3 to 5.3 days, as post-treatment of UASB effluents (domestic wastewater). Organic matter and solids were effectively and consistently removed, with average values of 70, 80 and 60% for TSS, BOD5 and COD, respectively. Nutrients removal, after a promising start up, became unstable and apparently influenced by temperature. The treatment system has also shown high potential to remove coliforms, although with relatively wide variations over the study period: ≈ 2 log10 reduction of total coliforms and 2-4 log10 reduction of Escherichia coli.

Quantitative microbial risk assessment applied to irrigation of salad crops with waste stabilization pond effluents.

A quantitative microbial risk assessment model for estimating infection risks arising from consuming crops eaten raw that have been irrigated with effluents from stabilization ponds was constructed. A log-normal probability distribution function was fitted to a large database from a comprehensive monitoring of an experimental pond system to account for variability in Escherichia coli concentration in irrigation water. Crop contamination levels were estimated using predictive models derived from field experiments involving the irrigation of several crops with different effluent qualities. Data on daily intake of salad crops were obtained from a national survey in Brazil. Ten thousand-trial Monte Carlo simulations were used to estimate human health risks associated with the use of wastewater for irrigating low- and high-growing crops. The use of effluents containing 10(3)-10(4) E. coli per 100 ml resulted in median rotavirus infection risk of approximately 10(-3) and 10(-4) pppy when irrigating, respectively, low- and high-growing crops; the corresponding 95th percentile risk estimates were around 10(-2) in both scenarios. Sensitivity analyses revealed that variations in effluent quality, in the assumed ratios of pathogens to E. coli, and in the reduction of pathogens between harvest and consumption had great impact upon risk estimates.

Wastewater irrigation of salad crops: further evidence for the evaluation of the WHO guidelines.

This paper presents the results of an experiment on salad crop irrigation with waste stabilisation pond effluents, conducted in Southeast Brazil. Over about 18 months several trials were carried out using different effluent qualities to irrigate lettuce, kale, arugula, spinach, and green pepper. Equations for predicting the bacterial quality of irrigated crops (E.coli per gram) based on the irrigation water quality (E.coli per 100 mL) were derived for low and high growing crops. The quantitative microbial risk analysis (QMRA) technique, using pathogen-ingestion scenarios based on these field data and on official statistics of vegetables consumption in Brazil, was used to estimate infection risks arising from the consumption of wastewater irrigated crops. It is inferred that irrigation with effluents complying with the WHO guidelines for unrestricted irrigation should result in salad crops acceptable for consumption.

Post-treatment of UASB reactor effluent in waste stabilization ponds and in horizontal flow constructed wetlands: a comparative study in pilot scale in Southeast Brazil.

The results of a 20-month period study in Brazil were analyzed to compare horizontal-flow constructed wetlands (CW) and waste stabilization pond (WSP) systems in terms of land area requirements and performance to produce effluent qualities for surface water discharge, and for wastewater use in agriculture and/or aquaculture. Nitrogen, E. coli and helminth eggs were more effectively removed in WSP than in CW. It is indicated that CW and WSP require similar land areas to achieve a bacteriological effluent quality suitable for unrestricted irrigation (10(3) E. coli per 100 mL), but CW would require 2.6 times more land area than ponds to achieve quite relaxed ammonia effluent discharge standards (20 mg NH(3) L(-1)), and, by far, more land than WSP to produce an effluent complying with the WHO helminth guideline for agricultural use (< or =1 egg per litre).

Qualidade da água do Reservatório da Usina Hidrelétrica (UHE) de Peti, Minas Gerais

This work was developed at the Reservoir of the Hydroelectric Power Station (UHE) of Peti, located in the municipalities of Barao de Cocais, Santa Barbara and Sao Goncalo do Rio Abaixo, in Minas Gerais State, Brazil, from September 2004 to May 2005, to evaluate the influence of the land use around the reservoir upon water quality. For this purpose, five points in the reservoir representing the various land plant covers and uses were chosen and the following physical and chemical parameters were analyzed: Temperature, Dissolved Oxygen, Electric Conductivity, pH, Turbidity, Color, Total Solids, Fixed Total Solids, Volatile Total Solids and Total Solids in Suspension in three depths at each point of collection. The parameter Transparency was analyzed in each point. The results of water quality were divided into dry weather period (September, October, April and May), and rainy period (November, December, January, February and March). They usually showed a seasonal variation. In the rainy period, parameters such as solids, turbidity and color increased. A greater variation among the depths in the dry weather period was also observed. When going farther inside the reservoir (from upstream to downstream), parameters such as turbidity, color and total solids in suspension decrease because of their dynamics. By the parameters analyzed, it was not possible to clearly detect the effect of the various land uses on the water quality.

Vigilância da qualidade da água para consumo humano: abordagem qualitativa da identificação de perigos

A necessidade de que os servicos de vigilância da qualidade da agua para consumo realizem sistematica/permanente avaliacao de risco dos sistemas de abastecimento e um importante desafio. Como a metodologia de Avaliacao de Risco ainda nao se encontra estruturada para rotineira utilizacao, apresenta-se uma sugestao de identificacao de perigos e categorizacao de riscos associados ao abastecimento de agua, atraves da utilizacao da metodologia proposta no Manual de Procedimentos de Vigilância em Saude Ambiental Relacionada a Qualidade da Agua para Consumo Humano, com modificacoes. Foram identificadas situacoes de perigo na saida do tratamento e na rede de distribuicao do sistema estudado. A aplicacao da metodologia permitiu uma visao abrangente do sistema de abastecimento e informacoes para planejamento/priorizacao de medidas de forma a reduzir os perigos identificados e possiveis riscos a saude da populacao.

Drinking water standards in South American countries: convergences and divergences

In this paper we present a comparative assessment of drinking-water standards from almost all South American countries, using the USA and the Canadian standards and the World Health Organization (WHO) Guidelines as references. Similarities and discrepancies between standards/guidelines were identified through descriptive analyses and, in the case of chemical standards, clustering techniques. In general, one or another of the four consecutive editions of the WHO Guidelines were shown to be quite influential in setting drinking-water standards in the region, but not so much the USA and the Canadian standards. Considerable discrepancies between South American drinking-water standards were found, mainly with respect to chemical substances. Questions are raised about their scientific basis and/or the practicalities for their enforcement. In conclusion, the paper highlights that many drinking-water regulations in South America need updating, taking on the approach of health-based targets in setting these standards, as well as that of a broader risk-based preventive management in the entire supply system to assure water safety.

UASB-polishing ponds design parameters: contributions from a pilot scale study in southeast Brazil

This paper presents the results of five years monitoring of an experimental wastewater treatment plant in southeast Brazil, comprised of a UASB reactor followed by a submerged aerated biofilter (BF) (field scale) and shallow polishing ponds (pilot scale). Three ponds in series achieved high quality effluent standards in terms of ammonia and E.coli, but a fourth pond did not result in further efficiency. Well established models to predict ammonia and E.coli removal in facultative and/or maturation ponds were, in a way, validated for polishing ponds too. The paper also includes results of input design parameters, such as pH and E.coli die-off rate constants, and their variation along the pond series.

Further contributions to nitrogen removal modelling in waste stabilization ponds.

A large database from an experimental maturation pond system in Brazil was used to verify the agreement of field results with values predicted by some of the most widely accepted models to describe ammonium and total nitrogen (TN) removal in facultative and maturation ponds. The same database was used to derive a pH-independent linear model to predict ammonium removal in ponds, which was proved to be, essentially, a function of ammonium surface loading rate. In general, all these models made reasonable predictions of ammonium or TN removal but tended to overestimate low ammonium effluent concentrations while underestimating higher values of field data.

Vigilância da qualidade da água para consumo humano no âmbito municipal: contornos, desafios e possibilidades

A amplitude das atribuicoes da vigilância da qualidade da agua para consumo humano (VQACH) associada a heterogeneidade dos municipios brasileiros (perfil demografico e epidemiologico, recursos humanos e financeiros) impoe ao nivel local de gestao o desafio de implementar com efetividade e sustentabilidade as acoes previstas no modelo de atuacao da VQACH. Tendo como cenario de estudo um municipio mineiro de pequeno porte, o trabalho apresenta desafios e possibilidades vivenciados durante a implementacao do modelo. O atendimento as acoes estrategicas e basicas e aos principios doutrinarios, organizacionais e executivos previstos no modelo de atuacao foi verificado e as estrategias para o enfrentamento dos desafios impostos ao exercicio da VQACH foram apresentadas. A conformacao de uma equipe de profissionais em quantidade e qualidade compativeis com as acoes de VQACH foi aspecto fundamental, alem da melhor explicitacao de procedimentos como analise integrada dos sistemas de informacao e analise e classificacao do grau de risco a saude das diferentes formas de abastecimento de agua. O estudo permite adiantar aos gestores dos diferentes niveis de governo desafios e estrategias para contorna-los, bem como instrumentaliza a coordenacao da VQACH no nivel federal sobre questoes que necessitam tratamento mais detalhado e especifico.