Sílvia Maria Alves Corrêa Oliveira

Avaliação de 166 ETEs em operação no país, compreendendo diversas tecnologias. Parte 1: análise de desempenho

The paper analyses the performance of 166 wastewater treatment plants operating in Brazil. Six different treatment technologies have been investigated, comprising the following processes: septic tank + anaerobic filter, facultative pond, anaerobic pond + facultative pond, activated sludge, UASB reactors alone, UASB reactors followed by post-treatment. The objective of the research was to evaluate the effluent quality and the removal efficiencies of the parameters BOD, COD, TSS, coliforms, TKN and phosphorus. The paper compares the effluent quality and the removal efficiencies with typical values reported by the technical literature. In general, the performance in the removal of organic matter was as expected. TSS removal efficiencies were lower than reported, but coliform removal was higher than described in the literature. Nutrient removal was low, but none of the treatment processes have been designed with this objective.

Comparative performance evaluation of full-scale anaerobic and aerobic wastewater treatment processes in Brazil

This article evaluates and compares the actual behavior of 166 full-scale anaerobic and aerobic wastewater treatment plants in operation in Brazil, providing information on the performance of the processes in terms of the quality of the generated effluent and the removal efficiency achieved. The observed results of effluent concentrations and removal efficiencies of the constituents BOD, COD, TSS (total suspended solids), TN (total nitrogen), TP (total phosphorus) and FC (faecal or thermotolerant coliforms) have been compared with the typical expected performance reported in the literature. The treatment technologies selected for study were: (a) predominantly anaerobic: (i) septic tank + anaerobic filter (ST + AF), (ii) UASB reactor without post-treatment (UASB) and (iii) UASB reactor followed by several post-treatment processes (UASB + POST); (b) predominantly aerobic: (iv) facultative pond (FP), (v) anaerobic pond followed by facultative pond (AP + FP) and (vi) activated sludge (AS). The results, confirmed by statistical tests, showed that, in general, the best performance was achieved by AS, but closely followed by UASB reactor, when operating with any kind of post-treatment. The effluent quality of the anaerobic processes ST + AF and UASB reactor without post-treatment was very similar to the one presented by facultative pond, a simpler aerobic process, regarding organic matter.

Performance evaluation of UASB reactor systems with and without post-treatment.

This article evaluates and compares the actual behavior of 18 UASB reactor systems operating without (10 plants) and with (8 plants) post treatment, considering their performance and their reliability in terms of compliance with specified discharge standards. The following types of post-treatment processes were analyzed: aerated filter; anaerobic filter; trickling filter; dissolved air flotation unit; facultative pond and maturation pond. The effluent quality and the removal efficiencies were compared with typical values reported in the technical literature. A methodology developed by Niku et al. (1979) was used for the determination of the coefficients of reliability, in terms of the compliance of effluent BOD and TSS with discharge standards. The results showed that, in general, the inclusion of a post-treatment step, be it either aerobic, anaerobic or physical-chemical, can provide a substantial improvement of the effluent quality from UASB reactors in terms of BOD and TSS. In terms of the systems reliability, the actual effluent concentrations from UASB reactor followed by some post-treatment processes would meet more restrictive discharge standards than those considered in this study (60 mg L(-1) for both constituents-values prevailing in most states in Brazil).

Avaliação de 166 ETES em operação no país, compreendendo diversas tecnologias. Parte 2: influência de fatores de projeto e operação

O estudo avalia a influencia de fatores de projeto e de operacao no desempenho de estacoes de tratamento de esgotos, considerando a concentracao efluente e eficiencia de remocao de DBO. Apenas quatro das seis tecnologias de tratamento estudadas na Parte 1 forneceram dados suficientes para analise: lagoas facultativas, lagoas anaerobias seguidas por lagoas facultativas, lodos ativados e reatores UASB operando isoladamente. O objetivo da pesquisa foi verificar a influencia das condicoes de carga (sobrecarga, carga adequada e subcarga), do porte da estacao e do envolvimento operacional (tendo como indicador a frequencia de monitoramento) no desempenho das estacoes de tratamento. Os resultados mostraram que nao existe uma relacao consistente entre a eficiencia de remocao e as variaveis operacionais. A contribuicao e a influencia de cada variavel difere de ETE para ETE, e pode ser resultado de projeto, operacao ou ambos.

Lognormal behaviour of untreated and treated wastewater constituents

This article presents an extensive study to select the theoretical probability distribution that represents the concentrations of major constituents from 35 wastewater treatment plants located in Brazil, as well as to verify the influence of the adopted treatment technology on the data distributions. Due to the lack of a solid basis for selecting the distributions that best fit the data, various distributions had to be tried and the choice was based on statistical tests and visual techniques, comprising a total of 3,444 tests undertaken. While comparing suitability of five distributions (normal, lognormal, gamma, exponential and rectangular) for analysis of data (influent and effluent biochemical oxygen demand, chemical oxygen demand, suspended solids, nitrogen, phosphorus, thermotolerant coliforms and flow), it was observed that the lognormal distribution was the most suitable, which is in agreement with the findings from other research studies. This conclusion requires a different position from the one currently adopted when analysing plant performance, in which symmetry of the data is generally implied, which has been shown not to be the case with the large array of data sets investigated.

Análise da confiabilidade de estações de tratamento de esgotos

This article presents a reliability analysis of 166 full-scale wastewater treatment plants operating in Brazil, comprising six different treatment processes usually adopted. A methodology developed by Niku et al (1979) is used for the determination of the coefficients of reliability (COR), in terms of the compliance of effluent BOD, COD, TSS, TN, TP and FC to discharge standards. The design concentrations necessary to meet the prevailing discharge standards and the expected compliance percentages have been calculated from the coefficients of reliability obtained. The results showed that few plants, under the observed operating conditions, would be able to present reliable performances in terms of compliance with the analyzed standards. For all constituents and systems, the variability of the effluent quality was very large.

Risk estimate of water contamination by pesticides used in coffee crops

ABSTRACT A study was conducted in Manhuacu city, Minas Gerais, aiming to study the effects of pesticides used incoffee crops on surface and ground waters. Manhuacu is located in an important Brazilian region ofagricultural production. Moreover, the city possesses many different water sources directed to the publicwater supply, and 13 points of surface and groundwater pumping. There have also been severaloccurrences of cancer in the local population. A survey conducted among cities of Minas Gerais identified122 cities with high occurrences of death due to cancer, among which was Manhuacu. The physico-chemical properties and applied mass of the active ingredients of each pesticide studied were surveyed.Goss and GUS algorithms were applied to estimate the risk of surface and ground water contamination,respectively. Some of the most widely used pesticides in the region, whose contamination potential wasestimated as high, were later detected in surface waters through LC/MS-MS. This study can helpagriculturists and officials of environmental organizations select and control, respectively, less harmfulproducts to the water.

The application of filterability as a parameter to evaluate the biological sludge quality in an MBR treating refinery effluent

AbstractMembrane bioreactors (MBR) have been extensively employed at industrial effluent treatment plants; however the membrane fouling has restrained its more extensive application. Filterability is an important parameter to evaluate sludge properties and the potentiality of membrane fouling in MBR, nevertheless the lack of standardization of its assessment method has made it difficult to understand its actual role on MBR performance and compare its results. In this context, this work aims to compare three filterability assessment methods described in the literature (TTF, FT, and SFI) regarding its capability to sense sludge quality variation and reproducibility, and evaluate the application of this parameter as a tool to monitor and control fouling in MBR treating petroleum refinery effluents. This study showed that, among the methods evaluated, time to filter was the most effective to assess the filterability, both in terms of its capability to sense sludge quality variation and reproducibility. The re...

Elements for setting up discharge standards in developing countries based on actual wastewater treatment plant performance

The paper analyses the capability of 166 full-scale wastewater treatment plants operating in Brazil, in order to achieve different quality targets for wastewater discharge. These targets cover a wide range of possible situations, reflecting usual practices adopted worldwide. Six different treatment processes have been investigated: septic tank+anaerobic filter, facultative pond, anaerobic pond+facultative pond, activated sludge, UASB reactors alone, UASB reactors followed by post-treatment. The parameters investigated were: BOD, COD, suspended solids, total nitrogen, total phosphorus and thermotolerant coliforms. Most technologies showed a poor performance, and some of them were not capable to achieve even relaxed standards. The paper presents elements for setting up discharge standards in developing countries, based either on values that may be achieved by treatment processes commonly applied or on best available technologies.

Nova abordagem do Índice de Qualidade de Água Bruta utilizando a Lógica Fuzzy

For the performance evaluation of water treatment plants, the raw water quality presents significant relevance. In Brazil, the Index of Quality of Raw Water for Public Supply (IAP) and the Index of Quality of Raw Water (IQAB), developed according to deterministic models, can evaluate the treatability of natural waters. However, the IAP presents a high cost for actual implementation and the IQAB needs some adjustments related to the input parameters and grading criteria. Aiming at a non-deterministic model, able to deal with uncertain, nonlinearity of the parameters and expert knowledge, Fuzzy Logic was applied to a new approach of the IQAB. The Fuzzy Raw Water Quality Index (IQABF), in comparison with the original IQAB, presented more restrictive, more consistent and more flexible for future adjustments. Its application for six water sources of Southeast Region showed practically the same hierarchy in terms of the treatability in comparison with the original IQAB.