Comparison of commercial disinfectants and an in loco-produced solution: free residual chlorine decay in human supply waters

Disinfection process is used in the treatment of water for human supply to promote sanitary safety and provide users with drinking water that meets potability standards. Thus, it is necessary to sustain a minimal concentration of free residual chlorine (FRC) throughout the entire distribution system. The present study investigated the decay process of FRC concentration in water destined for human supply. The decay was evaluated in bench-scale testing, using sodium hypochlorite, calcium hypochlorite, sodium dichloroisocyanurate (organic chlorine) as disinfectant agents, and also an alternative disinfectant solution (ADS) produced in loco, with oxidizing and disinfectant properties, which is being used in Brazilian sanitation industry. To evaluate the decay, four models were fitted: first-order, nth-order, limited first-order and parallel first-order, hence determining the corresponding parameters which describe the decay speed of the FRC concentration in water. Achieved results demonstrated that all models were statistically significant and predictive. However, parallel first-order model produced the best fit. Regarding the evaluated disinfectants, it was noted the preeminence of ADS solution when compared to the others, since it imparted a higher FRC over time, a behavior indicated by lower values for reaction rate constant in all models and when compared to other disinfectants used in this study.

Optimal Placement and Operation of Chlorine Booster Stations: A Multi-Level Optimization Approach

Chlorine demand as a disinfectant for water utility impacts on unintended energy consumption from electrolysis manufacture; thus, diminishing the chlorine consumption also reduces the environmental impact and energy consumption. Problems of disinfectant distribution and uniformity in Water Distribution Networks (WDN) are associated with the exponential urban growth and the physical and biochemical difficulties within the network. This study optimizes Chlorine Booster Stations (CBS) location on a network with two main objectives; (1) to deliver minimal Free Residual Chlorine (FRC) throughout all demand nodes according to country regulations, and (2) to reduce day chlorine mass concentration supplied in the system by applying an hour time pattern in CBS, consequently associated economic, energy and environmental impacts complying with regulatory standards. The application is demonstrated on a real-world WDN modeled from Guanajuato, Mexico. The resulting optimal location and disinfectant dosage schedule in CBS provided insights on maintaining disinfectant residuals throughout all the WDN to prevent health issues and diminishing chlorine consumption.

Physical-chemical and microbiological quality of water used for public supply in the municipality of Alvorada D’Oeste, Rondônia, Brazil

The study analyzed the physical-chemical and microbiological parameters carried out by the Autonomous Water and Sewage Service (AWSS) of the Municipality of Alvorada D’Oeste, Rondônia, Brazil. The parameters analyzed were: pH, turbidity, free residual chlorine, total coliforms (TC), thermotolerant coliforms (TTC) and heterotrophic bacteria. The values of hydrogen potential (pH) were obtained with a digital pH meter. The analyzes were carried out the 2013 to 2019. The turbidity and free residual chlorine values were obtained according to the method of the Practical Manual of Water Analysis of the National Health Foundation (FUNASA). To determine the microbiological parameters, PetrifilmTM plates (3MTM do Brasil Ltda) were used, following the manufacturer's guidelines. The analyzed values were compared with reference values described in Consolidation Ordinance nº. 5, of September 28, 2017, of the Ministry of Health (MS) which sets the standards for potability of water intended for human consumption. The results varied for all parameters evaluated: pH (3.11 to 8.24), turbidez (0.02 to 3,01), TC (0 to 100%), TTC (0 to 100%) and heterotrophic bacteria (85 to 100%). The values obtained for free residual chlorine were the only parameter to follow the reference values. The highest contamination for TC and heterotrophic bacteria were reported in 2019, higher the limits established in Brazilian legislation. Thus, the water was characterized as unfit for consumption and requires severe control for TC and heterotrophic bacteria.

Decay of Free Residual Chlorine in Wells Water of Northern Brazil

The concentration of chlorine in water declines as it reacts with various substances, causing decay of the residual free chlorine until its total consumption. In light of the typical characteristics of the water from protected dug wells and tube wells, this study aimed to evaluate the decay kinetics of free chlorine in the water of alternative individual supply (AIS) solutions used in the city of Porto Velho in the Brazilian Amazon region. The free chlorine decay constant in the water was evaluated by “bottle tests,” applying a first-order model. According to the results, the type of well and initial chlorine concentration significantly influences the free chlorine decay speed. The water samples from the tubular wells had lower chlorine demand levels, attributed to their better water quality. The simulation of the residual chlorine decay in the different supply sources is an important tool to support safe disinfection processes.

Study of the free residual chlorine concentration in drinking water in Benin: case of Cotonou municipality

The drinking water is very qualitatively monitored. Despite this monitoring, there is a deterioration in the Free Residual Chlorine Concentration (CCRL) along the drinking water distribution network of the commune of Cotonou. The objective of studying areas of consumer vulnerability where the CCRL reaches critical thresholds (<0.1 mg / l). To achieve this, water samples were taken from various locations in the supply network every day, from 04/30/2018. The assay method used is called N-Diethyl-P-phenylene Diamine (DPD) with the use of a DR / 890 colorimeter. This work reveal that the CCRL undergoes degradation during its delivery to the consumer's taps with average concentrations mainly above the standard in force [0.1; 0.8 mg / l] at the 5% threshold. The work made it possible to establish a linear model for predicting CCRL concentration as a function of distance and to identify areas of vulnerability in the study area. L’eau de consommation est très surveillée sur le plan qualitatif. En dépit de cette surveillance, on constate une dégradation de la Concentration en Chlore Résiduel Libre (CCRL) le long du réseau de distribution d’eau potable de la commune de Cotonou. L’objectif d’étudier les zones de vulnérabilité du consommateur où la CCRL atteint des seuils critiques (< à 0,1 mg /l). Pour y parvenir, des prélèvements d’échantillons d’eau ont été pris à divers endroits du réseau d’approvisionnement chaque jour, du 1er au 30/04/2018. La méthode de dosage utilisée est dénommée N-Diéthyl-P-phénylèneDiamine (DPD) avec usage d'un colorimètre DR/890. Ce travail à révéler, que la CCRL subi une dégradation lors de son acheminement vers les robinets du consommateur avec des concentrations moyennes majoritairement supérieures à la norme en vigueur [0,1 ; 0,8 mg/l] au seuil de 5%. Le travail a permis d’établir un modèle linéaire de prédiction de la concentration en CCRL en fonction de la distance et d’identifier les zones de vulnérabilité de la zone d’étude.

Pencil graphite as electrode platform for free chlorine sensors and energy storage devices

Multifunctional and low-cost electrode materials are desirable for the next-generation sensors and energy storage applications. This paper reports the use of pencil graphite as an electrode for dual applications that include the detection of free residual chlorine using electro-oxidation process and as an electrochemical energy storage cathode. The pencil graphite is transferred to cellulose paper by drawing ten times and applied for the detection of free residual chlorine, which shows a sensitivity of 27 μA mM-1 cm-2 with a limit of detection of 88.9 μM and linearity up to 7 mM. The sample matrix effect study for the commonly interfering ions such as NO3-, SO42-, CO32-, Cl-, HCO3- shows minimal impact on free residual chlorine detection. Pencil graphite then used after cyclic voltammogram treatment as a cathode in the aqueous Zn/Al-ion battery, showing an average discharge potential plateau of ~1.1 V, with a specific cathode capacity of ~54.1 mAh g-1 at a current of 55 mA g-1. It maintains ~95.8% of its initial efficiency after 100 cycles. Results obtained from the density functional theory calculation is consistent with the electro-oxidation process involved in the detection of free residual chlorine, as well as intercalation and de-intercalation behavior of Al3+ into the graphite layers of Zn/Al-ion battery. Therefore, pencil graphite due to its excellent electro-oxidation and conducting properties, can be successfully implemented as low cost, disposable and green material for both sensor and energy-storage applications.

Evaluation of water quality and sanitation of reservoirs used in field activities of a military unit in the state of Rio de Janeiro

In the Armed Forces' campaign activities, large troops may be exposed to serious health risks even before war itself. In 2010, for example, the Brazilian Army sent nearly 2,000 men to join the United Nations peacekeeping mission in Haiti, which was experiencing a cholera epidemic. This work therefore investigated the water quality and sanitation of the various types of reservoirs used in four field-training activities of a Brazilian Army Unit located in the state of Rio de Janeiro. Physicochemical and microbiological analyses of the water were carried out, and visual inspections and swab samples were collected from the inner surface of these reservoirs for counting coliform bacteria and counting mesophilic aerobic microorganisms. Physicochemical and microbiological analyses of water from different types of reservoirs revealed a lack of conformity with American Public Health Association and Ordinance Number 518, of 03/25/04, of the Brazilian Ministry of Health . It was observed that 50% of the collective and individual reservoirs did not have the desirable minimum levels of Free Residual Chlorine. In addition, in 35.7% of the total collective and individual reservoirs evaluated there was growth of coliform group bacteria and in 28.57% of them the number of heterotrophic bacteria exceeded the maximum recommendation. According to the swabs performed on the inner surfaces, results of the total viable mesophilic aerobic counts were above the recommended levels in 78.57% of the total evaluated reservoirs. Besides that, in the Lyster bags of activities 1 and 2, there was growth of coliforms, or 14.28% of the total evaluated reservoirs. It was concluded that there were failures in the management of multiple barriers during storage and / or distribution, as well as in the maintenance of disinfection to prevent or eliminate microbial contamination, indicating the need for corrective measures.

Broad Diversity of Fungi in Hospital Water

Introduction. Some studies have reported the occurrence of microorganisms isolated from water. Considering these microorganisms, fungi are known to occur ubiquitously in the environment, including water, and some are pathogenic and may cause health problems, especially in immunocompromised individuals. The aim of this study was to identify fungi in hospital water samples and to correlate their presence with the concentration of free residual chlorine. Methods. Water samples (100 mL) were collected from taps (n = 74) and water purifiers (n = 14) in different locations in a university hospital. Samples were filtered through a nitrocellulose membrane and placed on Sabouraud dextrose agar and incubated for 24 hours at 30∘C. Fungi were identified according to established methods based on macroscopic and microscopic characteristics (filamentous) and physiological tests (yeasts). Free chlorine residual content was measured at the time of sample collection. Results. Seventy species of fungi were identified in the water samples and about 56% of the water samples contained culturable fungi. Cladosporium oxysporum, Penicillium spinulosum, and Aspergillus fumigatus were the most common filamentous fungi. Aureobasidium pullulans and Candida parapsilosis were the most common yeasts. Chemical analyses revealed that free residual chlorine was present in 81.8% of the samples within recommended concentrations. Among samples from water purifiers, 92.9% showed low levels of free residual chlorine (<0.2 mg/L). There was no significant association between chlorine concentrations (either within or outside the recommended range) and the presence of filamentous fungi and yeasts. Conclusions. This study showed that hospital water can be a reservoir for fungi, some of which are potentially harmful to immunocompromised patients. Free residual chlorine was ineffective in some samples.