RESUMO
Post-treatment of anaerobic reactor effluent with maturation ponds is a good option for small to medium-sized communities in tropical climates. The treatment line investigated, operating in Brazil, with an equivalent capacity to treat domestic sewage from 250 inhabitants, comprised a upflow anaerobic sludge blanket reactor followed by two shallow maturation ponds (unbaffled and baffled) and a granular rock filter (decreasing grain size) in series, requiring an area of only 1.5â m2â inhabitant-1. With an overall hydraulic retention time of only 6.7 days, the performance was excellent for a natural treatment system. Based on over two years of continuous monitoring, median removal efficiencies were: biochemical oxygen demand = 93%, chemical oxygen demand = 79%, total suspended solids = 87%, ammonia = 43% and Escherichia coli = 6.1 log units. The final effluent complied with European discharge standards and WHO guidelines for some forms of irrigation, and appeared to be a suitable alternative for treating domestic sewage for small communities in warm areas, especially in developing countries.
Assuntos
Reatores Biológicos , Eliminação de Resíduos Líquidos/métodos , Amônia , Anaerobiose , Análise da Demanda Biológica de Oxigênio , Brasil , Filtração/métodos , LagoasRESUMO
Accumulated sludge in polishing (maturation) ponds reduces the hydraulic retention time (smaller useful volume), and this could potentially lead to a decrease in performance. However, settled biomass, present in the sediments, can contribute to nitrogen removal by different mechanisms such as nitrification and denitrification. This study investigated the influence of the bottom sludge present in a shallow maturation pond treating the effluent from an anaerobic reactor on the nitrification and denitrification processes. Nitrification and denitrification rates were determined in sediment cores by applying ammonia pulses. Environmental conditions in the medium were measured and bacteria detected and quantified by real-time polymerase chain reaction (real-time PCR). The pond showed daily cycles of mixing and stratification and most of the bacteria involved in nitrogen removal decreased in concentration from the upper to the lower part of the sludge layer. The results indicate that denitrifiers, nitrifiers and anammox bacteria coexisted in the sludge, and thus different metabolic pathways were involved in ammonium removal in the system. Therefore, the sediment contributed to nitrogen removal, even with a decrease in the hydraulic retention time in the pond due to the volume occupied by the sludge.
Assuntos
Nitrogênio/análise , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Reatores Biológicos , Brasil , Desnitrificação , LagoasRESUMO
This study presents a novel method for investigations on undisturbed samples from full-scale horizontal subsurface-flow constructed wetlands (HSSFCW). The planted fixed bed reactor (PFR), developed at the Helmholtz Center for Environmental Research (UFZ), is a universal test unit for planted soil filters that reproduces the operational conditions of a constructed wetland (CW) system in laboratory scale. The present research proposes modifications on the PFR original configuration in order to allow its operation in field conditions. A mobile device to obtain undisturbed samples from real-scale HSSFCW was also developed. The experimental setting is presented with two possible operational configurations. The first allows the removal and replacement of undisturbed samples in the CW bed for laboratory investigations, guaranteeing sample integrity with a mobile device. The second allows the continuous operation of the PFR and undisturbed samples as a fraction of the support media, reproducing the same environmental conditions outside the real-scale system. Investigations on the hydrodynamics of the adapted PFR were carried out with saline tracer tests, validating the proposed adaptation. Six adapted PFR units were installed next to full-scale HSSFCW beds and fed with interstitial liquid pumped from two regions of planted and unplanted support media. Fourteen points were monitored along the system, covering carbon fractions, nitrogen and sulfate. The results indicate the method as a promising tool for investigations on CW support media, rhizosphere and open space for studies on CW modeling, respirometry, kinetic parameters, microbial communities, redox potential and plant influence on HSSFCW.
Assuntos
Monitoramento Ambiental/métodos , Rizosfera , Poluentes Químicos da Água/análise , Áreas Alagadas , Reatores Biológicos , BrasilRESUMO
Stabilization ponds are a highly appropriate system for treating sewage in small to medium size communities. However, sludge accumulation at the pond bottom occurs with the passage of time, reducing the net pond volume, which, in principle, could affect its performance. The objective of this paper is to compare the behaviour of two equal ponds in parallel treating the same flow of municipal wastewater from an upflow anaerobic sludge blanket reactor in Brazil. Each pond treated a population equivalent of around 125 inhabitants. One pond had approximately 40% of its net volume occupied by sludge after 11 years of operation, while the other pond had previously undergone complete desludging. The study covers the removal of biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS), nitrogen fractions and coliforms. Owing to the presence of a sludge layer, the theoretical hydraulic retention time (HRT) was lower in the pond without sludge. For BOD, COD, SS and Escherichia coli there were no significant differences (Wilcoxon matched-pairs test) between both ponds. The pond without sludge had significantly better removal efficiencies in terms of total Kjeldahl nitrogen and ammonia-N. The sludge layer probably allowed the occurrence of removal mechanisms that compensated for the reduction caused in the HRT.
Assuntos
Esgotos/análise , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/análise , Anaerobiose , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Brasil , Cidades , Enterobacteriaceae/isolamento & purificação , Nitrogênio/análise , LagoasRESUMO
This paper presents a comparison between three simple sewage treatment lines involving natural processes: (a) upflow anaerobic sludge blanket (UASB) reactor-three maturation ponds in series-coarse rock filter; (b) UASB reactor-horizontal subsurface-flow constructed wetland; and (c) vertical-flow constructed wetlands treating raw sewage (first stage of the French system). The evaluation was based on several years of practical experience with three small full-scale plants receiving the same influent wastewater (population equivalents of 220, 60 and 100 inhabitants) in the city of Belo Horizonte, Brazil. The comparison included interpretation of concentrations and removal efficiencies based on monitoring data (organic matter, solids, nitrogen, phosphorus, coliforms and helminth eggs), together with an evaluation of practical aspects, such as land and volume requirements, sludge production and handling, plant management, clogging and others. Based on an integrated evaluation of all aspects involved, it is worth emphasizing that each system has its own specificities, and no generalization can be made on the best option. The overall conclusion is that the three lines are suitable for sewage treatment in small communities in warm-climate regions.
Assuntos
Reatores Biológicos , Esgotos , Eliminação de Resíduos Líquidos/métodos , Áreas Alagadas , Anaerobiose , Brasil , Filtração/métodos , Fósforo , Lagoas , Águas ResiduáriasRESUMO
This study investigated the behaviour of two intermittently fed vertical flow constructed wetlands (one planted with Tifton 85 and the other unplanted) working in parallel, treating raw municipal sewage in Brazil for a population equivalent around 100 inhabitants. Based on a monitoring programme of over 2 years, the following items were evaluated: influence of batch frequency and the presence of Tifton 85 on the wetlands performance in terms of several physico-chemical and biological constituents. The unit with plants performed better than the one without, indicating a positive influence of the presence of plants. More attachment by total and volatile solids and larger amount of bacteria involved in the nitrogen cycle were observed in the planted filter medium, which can explain its higher nitrification and solids removal. The application of a smaller influent volume with a higher batch frequency improved the performance of both units. No signs of medium clogging have been observed in both units. The system simplicity and the good removal efficiency of organic matter, suspended solids, ammonia and helminth eggs indicate its high applicability in small communities in developing countries such as Brazil.
Assuntos
Esgotos , Eliminação de Resíduos Líquidos/métodos , Áreas Alagadas , Amônia , Animais , Bactérias/metabolismo , Brasil , Características da Família , Filtração , Helmintos , Nitritos , Óvulo , Oxirredução , Purificação da ÁguaRESUMO
The objective of the work is to evaluate the performance of an innovative design of a trickling filter for small population sizes, which has been implemented for the post-treatment of sanitary effluent from a UASB (upflow anaerobic sludge blanket) reactor. The unit, named open trickling filter (OTF), operates with no side walls, no perforated bottom slab and no secondary settler. The OTF packing was 3.5 m high, composed of crushed stone, with a fixed distribution system made of channels with V-notch weirs. The OTF was operated with mean surface hydraulic loading rates of 4.1 and 9.3 m³ m⻲ d⻹, corresponding to population equivalents of approximately 250 and 550 inhabitants, respectively. For the surface hydraulic loading rate of 4.1 m³ m⻲ d⻹, the median removal efficiencies obtained by the OTF and overall system (UASB + OTF) were, respectively, 24 and 83% for total suspended solids (TSS), 44 and 79% for chemical oxygen demand (COD), 42 and 82% for biochemical oxygen demand (BOD), 40 and 40% for N-ammonia. For the surface hydraulic loading rate of 9.3 m³ m⻲ d⻹, the median removal efficiencies obtained by the OTF and global system (UASB + OTF) were 14 and 76% for TSS, 28 and 76% for COD, 25 and 86% for BOD, 15 and 15% for N-ammonia. Considering the great simplicity, no mechanization and small footprint of the system, these results can be considered satisfactory, suggesting that the OTF is suitable for small communities, especially in developing countries.
Assuntos
Cidades , Filtração/instrumentação , Amônia , Anaerobiose , Filtração/métodos , Eliminação de Resíduos Líquidos/métodosRESUMO
The purpose of this research was to determine the feasibility of a UV photoreactor for the disinfection of effluent from a polishing pond following a UASB reactor treating domestic wastewater. For this, a 20 mm diameter photoreactor (20.7 litre volume) equipped with four 30 W submerged low-pressure mercury arc lamps was used. Three tests with contact times and doses ranging from 45 to 90 s and from 16.9 to 31.3 mW s cm(-2) were carried out. Inactivation of total coliforms and Escherichia coli varied from 2.6 to 3.4 log-units, even with the presence of suspended solids in the range of 87 to 102 mg L(-1). These results have shown that UV radiation disinfection of pond effluents can be a feasible alternative in areas with land restriction.
Assuntos
Desinfecção/métodos , Enterobacteriaceae/efeitos da radiação , Raios Ultravioleta , Eliminação de Resíduos Líquidos/métodos , Poluentes da Água/efeitos da radiação , Reatores Biológicos , Contagem de Colônia Microbiana , Enterobacteriaceae/isolamento & purificação , Escherichia coli/isolamento & purificação , Escherichia coli/efeitos da radiação , Tamanho da Partícula , Poluentes da Água/isolamento & purificaçãoRESUMO
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.
Assuntos
Esgotos/química , Esgotos/microbiologia , Eliminação de Resíduos Líquidos/métodos , Purificação da Água/métodos , BrasilRESUMO
A sustainable option for nitrogen removal is the anaerobic ammonium-oxidizing (anammox) process in which ammonium is oxidized to nitrogen gas with nitrite as electron acceptor. Application of this process, however, is limited by the availability of anammox biomass. In this study, two Brocadia-like anammox phylotypes were successfully enriched, detected and identified from an activated sludge taken from a domestic wastewater treatment plant (Minas Gerais, Brazil) employing a Sequencing Batch Reactor (SBR). The dominant phylotype was closely related to 'Candidatus Brocadia sinica', but one clone seemed to represent a novel species for which we propose the name 'Candidatus Brocadia brasiliensis'. Based on Fluorescence in situ hybridization (FISH) analysis, this enrichment led to a relative population size of 52.7% (±15.6) anammox bacteria after 6 months of cultivation. The cultivation process can be divided into three phases: phase 1 (approximately 25 days) was characterized by heterotrophic denitrification metabolism, phase 2 was the propagation phase and phase 3 (from the 87th day onwards), in which significant anammox activity was detected. A long-term performance of the SBR showed a near perfect removal of nitrite based on the influent NO(2)(-)-N concentration of 61-95 mg L(-1). The average ammonia removal efficiency was 90% with the influent NH(4)(+)-N concentration of 55-82 mg L(-1). Therefore, anammox cultivation and enrichment from activated sludge was possible under a controlled environment within 3 months.