Residual Chlorine Concentration Research Articles

Foundry Odor Removal Using Hypochlorous Acid Aqueous Solution

In this paper, a method to deodorize ammonia and formaldehyde generated in a foundry using an aqueous solution of hypochlorous acid is reported. Air containing ammonia or formaldehyde was absorbed by an aqueous solution of hypochlorous acid, and the concentration of ammonia and formaldehyde before and after absorption, the type of ions in the solution, and the concentration of residual chlorine were measured. The results revealed that ammonia and formaldehyde deodorized upon oxidation in an aqueous solution of hypochlorous acid. However, the oxidation of formaldehyde with hypochlorous acid was only efficient in the presence of an adsorbent. The results have revealed the possibility of reducing foundry odors using a hypochlorous acid solution.

A Feasibility Study on Application of Eulerian Path Concept to Design of Water Supply Pipe Network

Objectives : This study attempted to investigated the advantages that can be obtained by applying the concept of ‘Eulerian path’ called ‘one-touch drawing’ to the block type water supply network which actually has been operating in Korea.Methods : This study applied the ‘Eulerian path’ concept to an actual water supply network, and suggested simple C language program for searching adjacency matrix. Five Eulerian path based design scenarios were derived using the C language program. The pressure and residual chlorine distribution pattern of five design scenarios and the existing small block network were simulated using EPANET and compared each other. Also, by comparing all scenarios construction costs, the economic feasibility related to initial investment cost was reviewed.Results and Discussion : Five Eulerian path scenarios with two or more closed pipe loops were suggested using the C language program checking out adjacency matrix. One of them(scenario 5) consists of 7 closed pipes that can supply water to all nodes even if the number of pipes is reduced by about 10, and an increase in residual chlorine concentration of about 0.01 mg/L can be predicted at each node. In addition, it is expected that the initial investment cost of Scenario 5 can be reduced by about 23%, compared to the initial investment cost of the existing small block.Conclusion : Therefore, by applying the concept of an Eulerian path to the design of a water supply pipe network, it is possible to economically eliminate meaningless pipes while maintaining the redundancy of water supply.

Analysis of Factors Involving Drinking Water Contamination by Glyphosate and/or Nitrate in Urban Areas

This study investigated factors that could be related to drinking water contamination in urban areas in order to obtain quality profiles that characterized presence of the glyphosate and nitrate contaminants. Thus, in a period of one year, 4,853 tap water samples from 89 cities in the northeastern region of the State of São Paulo, Brazil, were analyzed in 21 physicochemical and 2 microbiological parameters. Additionally, 4 demographic variables were also included in multivariate data analysis. Principal Component Analysis of physicochemical and microbiological data showed that glyphosate concentration is positively correlated with nitrate concentration, especially in cities that make exclusive use of groundwater, besides correlating with conductivity and with concentrations of calcium, magnesium, fluoride, chloride, phosphate and free residual chlorine. The inclusion of demographic variables in Principal Component Analysis did not significantly change waters physicochemical profiles, but in cities that exclusive use groundwater for public supply the number of hospitalizations for diarrhea correlated positively with glyphosate, nitrate and chloride concentrations, in addition to conductivity. Linear Discriminant Analysis models involving 5 variables (conductivity and concentrations of calcium, magnesium, chloride and nitrate) were able to predict the cities vulnerability to groundwater contamination by nitrate.

Analysis of Residual Chlorine and Total Coliform on Consumers of Perumdam Maja Tirta, Mojokerto City

This study aims to determine the concentration of residual chlorine and net total Coliform distributed by Perumdam Maja Tirta Water Supply Company and received by consumers. Water samples were taken from 7 locations on the distribution network a residential area of Perumdam Maja Tirta, the first sample taken at the reservoir of the Water Treatment Plant of Perumdam Maja Tirta and six samples from consumers. The residual chlorine concentration data and Total Coliform were mapped using Surfer 16 Software, producing an iso concentration map in the form of contour lines. The results showed that the concentration of residual water chlorine received by consumers of Perumdam Maja Tirta Mojokerto City ranged from <LoQ 0.1 mg/L to 0.3 mg/L. The further away from the IPA, the concentration of residual water chlorine decreased. Total Coliform parameters ranged from <1.8 – 240/100 ml in water received by consumers of Perumdam Maja Tirta Mojokerto City. There is a need to improve the quality of water services to consumers regarding water treatment and distribution.

Bacterial community structure and metabolic activity of drinking water pipelines in buildings: A new perspective on dual effects of hydrodynamic stagnation and algal organic matter invasion

Eutrophication and algal blooms have become global issues. The drinking water treatment process suffers from pollution by algal organic matter (AOM) through cell lysis during the algal blooms. Nevertheless, it remains unclear how AOM invasion affects water quality and microbial communities in drinking water, particularly in the stagnant settings. In this study, the addition of AOM caused the residual chlorine to rapidly degrade and below the limit of 0.05 mg/L, while the NO2−-N concentration ranged from 0.11 to 3.71 mg/L. Additionally, total bacterial counts increased and subsequently decreased. The results of Biolog demonstrated that the AOM significantly improved the utilization capacity of carbon sources and changed the preference for carbon sources. Full-length 16S rRNA gene sequencing and network modeling revealed a considerable reduction in the abundance of Proteobacteria, whereas that of Bacteroidetes increased significantly under the influence of AOM. Furthermore, the species abundance distributions of the Microcystis group and Scenedesmus group was most consistent with the Mandelbrot model. According to redundancy analysis and structural equation modeling, the bacterial community structure of the control group was most positively regulated by the free residual chlorine concentrations, whereas the Microcystis group and Scenedesmus group were positively correlated with the total organic carbon (TOC) concentration. Overall, these findings provide a scientific foundation for the evolution of drinking water quality under algae bloom pollution.

Assessment of water, sanitation, and hygiene services in district health care facilities in rural area of Mekong Delta, Vietnam.

Access to sufficient water, sanitation, and hygiene (WASH) services is a crucial requirement for patients during therapy and general well-being in the hospital. However, in low- and middle-income countries, these services are often inadequate, resulting in increased morbidity and mortality of patients. This study aimed at assessing the current situation of WASH services in six District Health Care Facilities (DHCFs) in rural areas of the Mekong Delta provinces, Vietnam. The results showed that these services were available with inappropriate quality, which did not compromise the stakeholders' needs. The revealed WASH infrastructures have raised concerns about the prolonged hospital stays for patients and push nosocomial infections to a high level. The safety of the water supply was doubted as the high E. coli (> 60%) and total coliform incidence (86%) was observed with very low residual chlorine concentration (< 0.1mg/L) in water quality assessment. Moreover, water supply contained a high concentration of iron (up to 15.55mg/L) in groundwater in one DHCF. Technical assessment tool analysis proved that the improper management and lack of knowledge by human resources were the primary roots of the observed status WASH services. Improvement of the perceptions of WASH should be done for the hospital staff with collaboration and support from the government to prevent incidents in the future.

ANALYSIS OF RESIDUAL CHLORINE CONCENTRATION IN DISTRIBUTION NETWORK OF DRINKING WATER SUPPLY AT ISTANA DIENG II RESIDENCE OF MALANG, EAST JAVA, INDONESIA

The drinking water distribution network in Istana Dieng residence is categorized as an isolated network because it does not connect with the other water distribution networks provided by the Malang Water Company (Perusahaan Daerah Air Minum, PDAM). For this reason, the residual chlorine of the isolated distribution network needs to be monitored regularly. Aim: This study aims to observe residual chlorine distribution patterns and investigate the effect of distribution distance, pH, and temperature on residual chlorine concentration in the water distribution network. Methodology and Results: Analytical survey method with a cross-sectional approach was used in this study. The field survey results and the water analysis were inputted into the ArcGIS 10.6 software to generate an Isoconcentration map. Correlation and regression analysis were conducted using SPSS 16.0. Conclusion, significance and impact of study: The results showed that 65% of the residual chlorine concentration in the drinking water distribution network Istana Dieng residence did not meet the quality standard (&lt;0.2 mg/l). Twenty-six sample points showed a value of 0.1 mg/l, which was caused by the pipe's physical condition and the use of wells connected to the PDAM network. There was a significant correlation between distance and residual chlorine concentration. The significant correlation between pH and residual chlorine concentration showed a value of -0.690. The correlation between temperature and residual chlorine concentration was -0.633. It was proven that the lower the residual chlorine concentration, the higher the pH and temperature values in the distribution network.

Water as Source of Salmonella Species Contamination in Jordanian Broiler Farms

Broiler chickens are a major meat product worldwide. Maintaining the health of flocks is essential for poultry farming and it is critical to minimize exposure to waterborne pathogens. This study determined the extent of Salmonella spp. infections and identified sources of waterborne disease transmission at representative Jordanian broiler farms. We investigated 10 broiler farms located in five Jordanian Governorates; Amman, Irbid, Karak, Zarqa, and Madaba. Cloacal swabs were collected from chickens and water samples were collected from farm tanks, broiler house tanks, and drinking apparatus (drinkers) over three rearing cycles. Water was tested for pH and residual free chlorine. Salmonella spp. was isolated from the cloacal and water samples using biochemical methods and confirmed as Salmonella enterica serovar Enteritidis by PCR. Salmonella enterica serovar Enteritidis was detected at sampled farms at different percentages and the pathogen was found in 16.6% (15/90) of drinkers and 20% (30/150) of cloacal samples. The total and free residual chlorine concentrations in the water were lower than the recommended levels. The average pH was within the recommended values. This study concluded that S. Enteritidis is prevalent in broiler farms in Jordan. Thus, improved hygienic practices at broiler farms and the establishment of national water quality guidelines are necessary to decrease S. Enteritidis transmission in boiler farmers and thus enhance food safety in Jordan.

Performance Assessment for Increasing Connection Rates of Private Water Supply Operators in Cambodia

Private water supply operators (PWSOs) play an important role in extending piped water services in small cities in Cambodia. However, the connection rates to PWSOs are highly varied. Therefore, this study aimed to find the reasons for the low connection rates of PWSOs and to propose ways to increase the connection rates. The three PWSOs selected for this study supply water continuously, with sufficiently high pressure and good water quality except for the low concentration of residual chlorine, while the per capita supply volume varies significantly. Households with alternative water sources, namely rainwater and well water, consume less piped water than those without alternative water sources. Scattered service areas far away from water treatment plants had coverage rates that were lower than in compact service areas. The present connection costs and water tariffs are higher than those that non-connected households are willing to pay, though they pay high costs for bottled water. Due to the high variation in household income, connection fees and water tariffs are a financial burden for low-income households. Because the operating rates of the PWSOs are 21–47%, it is advised that PWSOs reduce their connection fees and water tariffs to obtain more connected households in their service areas.

Prediction of chlorine concentration of flows exiting pipe in cross junctions: experimental and numerical study

Abstract This paper aims to develop and validate an analytical equation to predict the concentration of residual chlorine exiting a typical pipe junction. In order to investigate the trend of the incoming flow rates before leaving the junction, experiments with inflow rates (North and West) ranging from 0.18 to 2.17 L/s, Reynolds numbers ranging from 14,324 to 110,780, and free chlorine concentrations ranging from 0.5 to 1.80 mg/L were performed. The results showed that flows tend to bifurcate rather than mix completely, and the bifurcation and mixing depend mainly on the relative flow rates entering the cross junction. Based on the experimental results, a dimensionless concentration (R) was estimated, allowing for predicting chlorine at the East outlet. Then, a solute mass balance was also performed within the cross junction to predict chlorine concentration at the South outlet. Finally, an adjustment of the R-value was performed by using 3D computational fluid dynamics (CFD), and the analytical equations were also validated with simulations. The standard k–ε turbulence model with enhanced wall treatment for modeling turbulence and near-wall effects, respectively, were used. More mixing models will improve water quality simulations to ensure proper control of chlorine and possible contaminants in water distribution systems.

Risk Assessment of Drinking Water Supply System of Talesh Based on World Health Organization Water Safety Plan in 2021: A Case Study

Water safety plan (WSP) is a new way to ensure the safety of drinking water by risk assessment and systematic prevention approach. The purpose of this study was to assess the risk and identify hazards from the production source to the point of use and plan to reduce or eliminate these hazards to provide safe drinking water. This study was conducted on the water supply system of Talesh city in 2021. The WSP has 12 stages and the third stage is risk assessment and hazard identification. This stage scored 69 points out of a total of 100 raw points, which indicates 69% coordination with the WSP. Based on the analysis, 47 hazards were identified in production sources, transmission lines, distribution network, and point of use. The presence of domestic sewage wells near the source of supply, undesirable chlorine concentration, and old pipes in the distribution network, as well as the failure of the check valve at the point of consumption are the most important risks. With the implementation of different phases of WSP, especially the stage of identification and assessment of microbial contamination risk in the distribution network, has been decreased to 0% and the desired residual chlorine concentration has been increased to 100%. Currently, water supply system of Talesh has a moderate level of safety.

An Automated Toolchain for Camera-Enabled Sensing of Drinking Water Chlorine Residual.

Chlorine residual concentration is an important parameter to prevent pathogen growth in drinking water. Disposable color changing test strips that measure chlorine in tap water are commercially available to the public; however, the color changes are difficult to read by eye, and the data are not captured for water service providers. Here we present an automated toolchain designed to process digital images of free chlorine residual test strips taken with mobile phone cameras. The toolchain crops the image using image processing algorithms that isolate the areas relevant for analysis and automatically white balances the image to allow for use with different phones and lighting conditions. The average red, green, and blue (RGB) color values of the image are used to predict a free chlorine concentration that is classified into three concentration tiers (<0.2 mg/L, 0.2-0.5 mg/L, or >0.5 mg/L), which can be reported to water users and recorded for utility use. The proposed approach was applied to three different phone types under three different lighting conditions using a standard background. This approach can discriminate between concentrations above and below 0.5 mg/L with an accuracy of 90% and 94% for training and testing data sets, respectively. Furthermore, it can discriminate between concentrations of <0.2 mg/L, 0.2-0.5 mg/L, or >0.5 mg/L with weighted-averaged F1 scores of 79% and 88% for training and testing data sets, respectively. This tool sets the stage for tap water consumers and water utilities to gather frequent measurements and high-resolution temporal and spatial data on drinking water quality.

Decay process of free residual chlorine concentration affected by travel time in water distribution systems

Chlorination is the most widely used method for disinfecting water for human consumption. While the chlorinated water travels through a distribution system, the concentration of free residual chlorine (FRC) declines depending on the natural water characteristics. This study investigated FRC decay in two types of water sources – ground and surface water – with varied concentrations of organic compounds. The travel time variable depended on water consumption patterns of both distribution systems which attend low density populations and their initial project needs. Based on mathematical simulation techniques of water quality models, the study also investigated the effects of water temperature and total organic carbon (TOC) on the kinetic constants (kb) of chlorine decay. Results show that travel time in the most critical locations in the water networks and the minimum disinfectant concentrations required at the entry points were 40 hours and 0.27-0.28 mg L-1 at Vale dos Pássaros housing complex, and 144 hours and 0.30-0.36 mg L-1 at Terras Alphaville housing complex.&#x0D; Keywords: disinfection, TOC, water quality.

Is your ice machine really clean? Uncovering the presence of opportunistic pathogens in hospital ice machines

Background: Ice is used in healthcare facilities for medical purposes and consumption by the medical staff and the patients, but some studies have revealed significant microbial contamination of ice machines leading to nosocomial outbreaks or pseudooutbreaks and infections by opportunistic pathogens, including the fungi Candida, the bacteria Pseudomonas aeruginosa, and nontuberculous mycobacteria (NTM). Although ice machines are complex devices that are prone to contamination, very little is known about their potential as vectors of infections for populations at risk in hospitals. Only few studies document efficient maintenance regimes, specifically cleaning procedures and microbial indicators that would ensure their safe use. Method: In this prospective study, combined samples of water and ice, and drain biofilm samples were collected from 36 ice and cold-water distribution machines of a recently built hospital, for a total of 72 samples. Physicochemical parameters (total and free chlorine, temperature, etc) were measured in water, and several opportunistic pathogens (ie, Candida spp, P. aeruginosa, NTM) and biological indicators (ie, heterotrophic plate counts (HPCs), total and viable bacteria and enterococci) were monitored in water and ice and biofilm. Culture methods were used for HPCs, Candida spp, P. aeruginosa, and enterococci, and total and viable bacterial populations were estimated using flow cytometry. NTM were monitored by quantitative polymerase chain reaction (qPCR). Results: We observed clear differences between the machines in terms of biological contamination, with frequent detection of NTM and presumed Candida. Thus, NTM were detected in the 36 samples of ice and water with concentrations from 0.5 to 2×104 gene copies/mL. Among the several species of fungi detected in the ice machines, some were identified as C. parapsilosis and C. guilliermondii, which are organisms of concern in healthcare facilities. Factors affecting the level of contamination in ice machines include the location of the machines and water quality (ie, temperature and chlorine residual concentration). Depending on the location in the building and the model of ice machine sampled, the biological indicators measurements indicated more or less significant contamination. No link was established between environmental strains recovered from the machines and clinical infections. Conclusions: Monitoring results showed that ice machines, while subject to few regulations and controls, can be reservoirs of unsuspected opportunistic pathogens that could lead to nosocomial infections of vulnerable patients. Cleaning procedures should be based on the disinfection of resistant opportunistic pathogens, such as Candida and NTM, and the use of general indicators, such as HPCs, should be questioned.Funding: NoneDisclosures: None

Induced Circulation by Plunging and Submerged Jets in Circular Water Storage Tanks Using CFD

Water circulation in storage tanks significantly impacts water quality in distribution networks since old water tends to have low residual chlorine concentrations that are insufficient to neutralize microbial regeneration. Their large capacity and long residence times result in uneven mixing, which can accelerate the disinfectant decay and the formation of potentially carcinogenic disinfection by-products. The phenomenon is strongly related to the tank inflow conditions, since there are no active mixing devices. This paper presents a comprehensive analysis of the flow dynamics in circular storage tanks using a three-dimensional computational fluid dynamics model. The main motivation is that the inflow—which mixing processes rely on—strongly influences the circulations. The numerical analysis provided includes a thorough investigation of interest in understanding flow dynamics for two inflow configurations: (i) the plunging jet modelling and comparison with published experimental data and (ii) the submerged jet as an improvement measurement for these storage tanks.

Evaluation of water quality and potential scaling of corrosion in the water supply using water quality and stability indices: A case study of Juja water distribution network, Kenya

Drinking water quality describes the conditions for water to be accepted as suitable for human consumption. The water quality index is characterized by including, in the assessment process, water quality parameters such as physical, chemical and micro-biological. The availability of adequate management strategies to maintain good quality water has always been a challenge for water utilities. To proffer a solution to ths problem, a simple and effective tool that can be used to easily assess the quality of water is required. Water Quality Index (WQI) and Water Stability Index (WSI) are the most reliable tools for assessing water quality and aggressiveness. This study, therefore assessed the water quality, potential scaling and corrosion of the water supply in the Juja water distribution network by using WQI and WSI based on Langelier Saturation Index (LSI). Five sampling locations including the treatment plant outlet and consumption points were selected for physical, chemical and bacteriological water quality analysis and determination of WQI and WSI. It was found that 100 % of the collected water samples had Calcium concentrations within the World Health Organization (WHO) and Kenya Bureau of Standards (KEBS) acceptable ranges.Additionally, all the collected water samples had TDS concentrations within the WHO and KEBS acceptable ranges. However, water quality parameters such as Residual Chlorine, E. coli, Alkalinity, and Turbidity deviated from the WHO and KEBS standards. The pH values ranged from 6.29 to 8.06 and were generally within acceptable limits. The WSI ranged between – 3.04 to – 0.99, indicating that the water is generally corrosive and may pose a risk to water quality and shorten the lifespan of the network facilities. Generally, the water from the Treatment Plant was of good quality, while at consumption points, JKUAT Main Gate, JKUAT Campus, High Point, and Juja Stage had fair water quality based on the calculated WQI. Also, low concentrations of residual chlorine and E. coli slightly dropped the water quality at all the stations. Overall, the water quality deteriorated in the distribution network and was corrosive throughout the system right from the Treatment Plant based on the WQI and WSI. The water company needs to improve on the water quality chemically by adjusting the Calcium and Alkalinity concentration up to 40 mg/L CaCO3 as recommended for stable water and relook at management strategies of the network to provide better services to consumers.

Solar-powered electrocoagulation treatment of wet flue gas desulfurization wastewater using dimensionally stable anode and induced electrode

Solar-powered electrocoagulation (EC) process is proven to be an alternative option for wet flue gas desulfurization (WFGD) wastewater treatment, due to simultaneous removal of multiple pollutants efficiently and reduce the operation costs significantly. Rapid and stable photoelectricity response is necessary for the removal efficiency of pollutants (eg. COD and turbudity), especially in low solar irradiation intensity. In this paper, dimensionally stable anode (DSA) and operation voltages in EC process driven by solar cells were investigated, for the purpose of the optimized removal of pollutants, including COD, turbidity, (free residual chlorine and chlorine dioxide). The results show that the removal efficiency of COD and turbidity can respectively reach 59.12% and 39.11% within 30 min of illumination time (the enhanced solar radiation = 915.8 W m-2), when Ti-based plates were adopted. The concentration of free residual chlorine and chlorine dioxide can reach 2.70 and 5.31 mg L-1, indicating that chlorine ions present in WFGD wastewater have been converted into active chlorine partly. Solar-powered EC equipped with Ti-based plates have a potential prospect in EC process for WFGD wastewater treatment.

Impact of pipe material on the wall reaction coefficients and its application in the rehabilitation of water supply system of San Pedro Nexapa, State of Mexico

Abstract One of the major challenges faced by water companies around the world is the high level of chlorine losses in distribution networks. This paper presents an experimental study to examine chlorine loss in different types of pipe materials and select the ones with low chlorine demand for the rehabilitation of the water distribution network of San Pedro Nexapa, State of Mexico. The materials investigated include: polyvinyl chloride (PVC), galvanized steel (GS), polypropylene (PP) and high-density polyethylene (HDPE). A 24-h chlorine consumption study was performed in a simulated water distribution network to assess the impact of wall reaction coefficient on chlorine decay. Four sets of independent pipe loops of 50 mm in diameter and 12 m in length were used. Two different scenarios were considered based on different initial chlorine concentration (1.21 mg/L and 1.60 mg/L). Samples were collected at each loop at two-hour intervals and physicochemical analyses were conducted. Results from the experimental distribution network showed that the wall coefficient values for GS, HDPE, PP and PVC were 0.165 h−1, 0.059 h−1, 0.043 h−1 and 0.026 h−1, respectively. Experimental results showed that wall reaction coefficient values depend on initial chlorine concentration and the characteristics of pipe material. The rate of free chlorine decay was found to be faster in steel pipe and slower in the plastic pipes. Based on its having the lowest chlorine demand compared with the other pipes, PVC pipe would be selected to rehabilitate Nexapa water distribution network, State of Mexico. The wall coefficients from the experimental study were incorporated into EPANET through four simulation runs to predict chorine decay of San Pedro Nexapa water distribution network, State of Mexico. In the PVC and PP pipes higher residual chlorine concentrations were observed that ranged from 0.30 to 0.90 mg/L and 0.50 to 0.95 mg/L, respectively. This study is important for utilities to operate their system effectively and protect public health.

Pollution Characteristics and Risk Assessment of DBPs in Typical Drinking Water Sources in Wuhan Under the COVID-19 Pandemic

In order to reveal the pollution characteristics and risk levels of DBPs in typical drinking water sources in Wuhan under the COVID-19 pandemic, 26 sampling sites were selected in typical drinking water sources in Wuhan. N,N-diethyl-1,4-phenylenediamine spectrophotometry and gas chromatograph-micro-cell electron capture detector (GC-μECD) methods were used to detect residual chlorine disinfectants and DBPs in water, respectively, and their health and ecology risks were assessed. The results showed that free chlorine or total residual chlorine were detected in 16 of the 26 water samples, and the maximum concentration was 0.04 mg·L-1, which exceeded the limit of the surface water standard in China. The concentration of residual chlorine was higher in sampling sites near the outfall of a municipal sewage plant. There were 34 types of DBPs measured in 10 sampling sites, and 24 types of substances were detected with the detection rate of 10.00%-100.00%. The ρ (total DBPs) was in the range of 0.11-104.73 μg·L-1, with an average value of 7.26 μg·L-1. The concentration of chloroform was the highest among all the DBPs, ranging from 9.98 μg·L-1 to 11.15 μg·L-1, with an average value of 10.47 μg·L-1. The concentration of 2-bromo-2-iodoacetamide was the lowest, ranging from ND-0.11 μg·L-1, with an average value of 0.01 μg·L-1. The overall detection level of the DBPs area was low in this study area, and the result of the health risk assessment showed that the DBPs had no carcinogenic or non-carcinogenic health risks to human body. However, the results of the ecological risk assessment showed that chloroform presented a high ecological risk to aquatic organisms.

Chlorine Efficiency in the Reducing Coliforms in the Sanitary Effluent of Septic Tank Treatment Systems with Anaerobic Filter

The lack of basic sanitation is still a problem in Brazil, only about half of all sewage produced undergoes treatment, due to difficulties in introducing sanitary effluent treatment plants considering that most Brazilian cities do not have financial resources for implementation and maintenance of these stations. In this way, many cities have been adopting different methods for treating sewage before discarding into the rain network. Thus, this work aimed to analyze the efficiency of chlorine in the reduction of coliforms in the sanitary effluent of a treatment system with septic tank, anaerobic filter and disinfection. Six sanitary sewage treatment systems were evaluated from different condominiums from august to december 2019. To check its efficiency, the following parameters were analyzed: pH, thermotolerant coliforms, free residual chlorine and chemical oxygen demand (COD). The results showed that of the six stations evaluated, only one (16,78%) presented the amount of thermotolerant coliforms within the permissible standards. Furthermore, of these only three stations (50%) presented the concentrations of free residual chlorine according to the required parameters. In addition, COD was high at four (66,66%) of the analyzed stations. These data allow us to conclude that the efficiency of chlorine in the reduction of coliforms in the sanitary effluent from a septic tank treatment system, anaerobic filter and disinfection unfortunately may not be happening, because this type of system needs to be well operated and inspected frequently, since the operation is mostly done by users.