Wastewater Treatment In Brazil Research Articles

Systematic review of the last 20 years of research on decentralized domestic wastewater treatment in Brazil: state of the art and potentials.

A DEWATS (decentralized wastewater treatment system) is an alternative for expanding sanitation. In Brazil, DEWATS is acknowledged by law and is part of the National Sanitation Plan strategy for achieving the treatment of 85.6% of all the generated wastewater by 2033, improving the current treatment index of 49%. This review's aim is to identify DEWATS studies in Brazil and to verify their potential for narrowing the national wastewater treatment deficit. Hence, aspects such as cost, maintenance, and efficiency were assessed. The archival research method (ARM) was used to identify papers published in the last 20 years through the scientific databases of Scopus, Science Direct, and Web of Science. Data regarding the general characteristics of each study were collected and compared to Brazilian environmental regulation and sanitation status. The results showed the evaluation of different technologies such as DEWATS, highlighting their flexibility and potential use in 79% of Brazilian counties. However, although 81% of the studies conducted performance analysis, none covered the main parameters required by Brazilian law. Although legal gaps for DEWATS improvement and consolidation have been identified and the interest in studying DEWATS has been increasing in the last five years, many barriers to their widespread use remain.

Detection and removal of Giardia spp. cysts and Cryptosporidium spp. oocysts by anaerobic reactors in Brazil

ABSTRACT The discharge of raw wastewater into the environment can be a contamination source of Giardia spp. cysts and Cryptosporidium spp. oocysts. The UASB (Upflow Anaerobic Sludge Blanket) reactor is the most popular technology applied for wastewater treatment in Brazil, nevertheless there is little information concerning its capacity for (oo)cyst removal. In this context, this study investigated the occurrence and removal of Giardia spp. cysts and Cryptosporidium spp. oocysts by three different UASB reactors (i.e. Reactor A, B, and C) treating different wastewater types. In the wastewater influent, the concentration varied from 493.3 to 14,000 cysts·L-1 for Giardia spp. and from ‘not detected’ to 53.3 oocysts·L-1 for Cryptosporidium spp.. The (oo)cyst concentration increased after the anaerobic treatment in Reactors A and B, while Giardia spp. log-removal of 0.5 ± 0.2 was found in Reactor C. The increment in (oo)cyst concentration may happened due to the inefficacy for (oo)cyst removal by the specific UASB reactor and/or due to the reduction of matrix interference for reactor effluent samples in the detection method. The results suggest that hydraulic retention time (HRT) may be the key parameter for Giardia spp. removal by the UASB reactor. Furthermore, no parameter analysed (physical-chemical and indicator microorganisms) showed a common correlation with the (oo)cyst concentration in the three UASB reactors. Considering that official data of cryptosporidiosis and giardiasis cases are rarely reported in Brazil, monitoring Giardia spp. cysts and Cryptosporidium spp. oocysts in wastewater could be an alternative to estimate the occurrence of diseases in the served population.

Chlorine and peracetic acid in decentralized wastewater treatment: Disinfection, oxidation and odor control

Decentralized wastewater treatment is a viable and sustainable alternative to having universal access to sanitation, especially for developing countries and small communities. Chlorine and peracetic acid (PAA) have been studied widely to promote wastewater disinfection, however there are few comparative studies applied to decentralized wastewater treatments. This paper investigated the application of chlorine and PAA in two biological reactor effluents regarding disinfection, organic matter oxidation, and odor control. Full factorial design was used to quantify the effect of the Chlorine and PAA dose (5, 10, and 15 mg L−1) and contact time (5, 10, and 15 min) in the batch experiments. Chlorine and PAA were inefficient in reducing the organic matter showing an increment in the chemical oxygen demand (COD) concentration in most of the tests. Sulfide was oxidized by chlorine (0.0–39.9 %) and PAA (3.5–73.5 %) for both reactor effluents. Inactivation results from E. coli and total coliform by chlorine and PAA showed that the effluent quality has a stronger influence than the disinfectant type. The best operational condition (15 mg L−1, 15 min) were also tested in the continuous mode flow, whose results are in agreement with those found in the batch tests. These results provide valuable support in terms of establishing practical guidelines for chlorine and PAA applications in decentralized wastewater treatment in Brazil.

Microalgae cultivation for municipal and piggery wastewater treatment in Brazil

Microalgae are a source of high-valuable products covering a wide range of applications. However, costs incurred by cultivating them make it an expensive process. The combination of wastewater treatment and microalgae cultivation is a viable option to reduce expenses related to cultivation. However, municipal wastewater from the centralized Brazilian sanitation system is highly diluted, and it is technically and economically impractical to use it for microalgae cultivation. As an alternative, diluted effluent can be mixed with a different kind of wastewater, aiming to increase the nutrient concentration (carbon, nitrogen and phosphorus) for microalgae cultivation. In this study, microalgae cultivation and wastewater mixture (municipal and piggery wastewater) treatment were monitored for four weeks. The pilot treatment system consisted of UASB as pre-treatment and Chlorella sorokiniana cultivation in three flat panel photobioreactors. High UASB efficiency was obtained in organic matter removal (> 90%), even with a large variability of initial mixture characteristics. C. sorokiniana production reached about 1 g L−1, with an average removal of dissolved inorganic carbon, orthophosphate and ammonia around 46 to 56%, 40 to 60% and 100%, respectively. Possible solutions to improve the microalgae growth and the system treatment are discussed.

Vertical flow constructed wetland planted with Heliconia psittacorum used as decentralized post-treatment of anaerobic effluent in Southern Brazil

In order to investigate the potential of vertical flow constructed wetlands (VFCWs), a 24.5 m2 surface area filled with gravel and planted with Heliconia psittacorum, was implemented as an experimental system for domestic wastewater treatment in southern Brazil. The aims of the study were to (i) evaluate the performance of a full scale system septic tank (ST) and VFCW for decentralized domestic wastewater treatment, and (ii) identify the influence of Heliconia for hydraulic characteristics and consequent performance of the VFCW. The applied load rates in the VFCW were, on average, 10 g biochemical oxygen demand (BOD) m−2 day−1, 4 g NH4+-N m−2 day−1 and a hydraulic loading rate (HLR) of 60 mm day−1. Physicochemical analyses of wastewater treatment were carried out through grab sample methodology, for 5 months. Additionally, hydrodynamic tests were performed during plant development using rhodamine. The study demonstrated the viability of the system for decentralized wastewater treatment in Brazil, with average removal efficiencies of 78% for chemical oxygen demand (COD) and 84% for total suspended solids (TSS), according to national effluent discharge regulations. In spite of media’s large size, the VFCW achieved good average removal efficiencies. The tracer test results showed that the VFCW average hydraulic detention time increased as plants grew. This may have occurred due to interception of wastewater applied on the macrophyte’s leaves as well as a reduction in filter media permeability caused by the spread of roots and rhizomes. These results indicate that the plants played an important role in increasing wastewater contact time in wetlands with high hydraulic conductivity such as a gravel VFCW.

Simulação computacional do comportamento hidrodinâmico em lagoas facultativas com chicanas

Wastewater facultative ponds are used extensively to provide wastewater treatment in Brazil. While understanding the hydraulics of facultative ponds is critical to their optimization, there is a poor understanding of the behavior of the flow that exists within them. The objective of this study is to apply Computational Fluid Dynamics (CFD) modeling on waste stabilization ponds with many configurations including baffling. From the comparison of the results the following conclusions were drawn: (1) the flow for the geometry without baffles was characterized by high levels of short-circuiting and large re-circulation regions; (2) the use of baffles creates flow fields in the tanks which reduce short-circuiting and the re-circulating regions. Particularly, the results show that ponds with two longitudinal baffles are more effective in terms of hydrodynamic behavior because the use of baffles creates flow fields with significant volumes of “plug flow” and the regions with very low velocities are significantly diminished. Keywords: facultative ponds; baffling; hydrodynamic behavior; hydraulics

Wastewater treatment in Brazil: Institutional framework, recent initiatives and actual plant performance

Brazil, like many other developing countries, suffers from widespread pollution of the aquatic environment caused by the uncontrolled discharge of untreated urban wastewater. Some states have made greater progress towards the implementation of pollution mitigation strategies than others. However, a study undertaken in the states of So Paulo and Minas Gerais indicates that installation of treatment plants is not sufficient to meet effluent quality objectives. A range of different wastewater treatment processes were investigated and, although conclusive results were difficult to define due to the large differences in the frequency of sampling, the results showed a highly variable performance, in which many processes were not operating satisfactorily according to expected design performance or environmental standards set by the regulatory authority. In light of these findings, the paper discusses an innovative programme called PRODES, introduced by the National Water Agency (ANA), which aims to encourage public and private companies to implement new treatment plants and to improve the performance of existing wastewater treatment systems based upon a system of financial incentives according to the monitored reduction in pollutant loads. The paper concludes that this approach has considerable potential as part of a pollution mitigation strategy, but success is dependent on the development of a standardized framework for routine performance evaluation and monitoring to improve operational performance and regulatory procedures.

Pilot-Scale Experiments in Water Hyacinth Lagoons for Wastewater Treatment

Based on some information collected in foreign bibliography which classifies water hyacinth as one of the possible interesting alternatives for the treatment of some types of domestic sewage, CETESB has since 1980 been developing, in participation with other institutions, a series of pilot-scale experiments in order to evaluate the real applicability of this system of wastewater treatment in Brazil. The conclusions that can be drawn from the experiments that have been carried out up to the present have indicated that the water hyacinth lagoon presents a better performance when it is integrated with other treatment systems, mainly at tertiary level, instead of its direct application to raw sewage treatment. One of the operational problems of this system, which has been observed during the experiments, refers to the intense proliferation of mosquitos, the control levels of which were not satisfactory even with the periodical application of larvicide. The problem of water hyacinth removal and its use as biomass has not been solved at industrial level yet. In pilot-scale experiments carried out by CETESB, the use of water hyacinth as an organic compost has proved to be economically unfeasible, on an industrial scale, considering that there are many other residues which offer better alternatives both from the economical point of view and the available amounts.