The present work had as its objective, the evaluation of the combination of electrochemical, photochemical and sonrochemical techniques (sono-electrochemical photoassisted) applied to degradation of cytarabine (chemotherapeutic drug) in a simulated urine that continues with creatinine and laboratory research. The paper involved laboratory research with both a qualitative and quantitative approach. A continuous-flow filter-press electrochemical reactor was employed using Dimensionally Stable Anode (DSA® - Ti/Ru0.3Ti0.7O2) as the electrode material. A 23 factorial design was used to optimize the degradation of organic compounds contained in artificial urine (creatinine and urea) together with cytarabine, varying applied current, retention time and flow rate, the response variable was total organic carbon (TOC) removal. Additionally, UHPLC analyses demonstrated the removal of ancitabine (precursor of cytarabine), corroborating with the data obtained by the from the experimental design. The use of artificial urine as an electronic support interferes with the electrochemical process, taking TOC to high levels. However, it was observed that there was significant removal of the organic load present in the effluent solution, even when a more complex degradation matrix is used (artificial urine).
The efficiency of electrolysis (EC/Cl2) and photo-assisted electrolysis (EC/UV/Cl2) methods, in the presence of chloride, for the abatement of real dairy waste from a producer in the Triangulo Mineiro region of Brazil, was evaluated. A complete 23 factorial design was performed for the variables time, pH and current. After determining the ideal pH, a Central Compound Design (CCD) was performed, where the applied current (533.42 mA) and treatment time (60.45 minutes) were maximized. The effluent was subsequently submitted to prolonged EC/Cl2 and EC/UV/Cl2 treatment in order to evaluate the behaviour of specific environmental parameters over time. The EC/UV/Cl2 method was more efficient than simple EC/Cl2 treatment. The EC/UV/Cl2 method resulted in a reduction of all environmental parameters investigated to levels within legal standards for effluent discharge. A relatively low cost of treatment is obtained with Energy per Order (EEO) values of 0.89 and 1.22 kWh m−3 order−1 for the EC/UV/Cl2 and EC/Cl2 treatments, respectively. The electrochemical production of free chlorine species followed by subsequent photolysis and production of radical species can convert a simple electrochemical process into an advanced oxidation process (AOP).
Few studies employ electrochemical technology for urban water disinfection. This paper presents the replacement of a Cl 2 gas system by an on-site chlorine generation system (electrochemical disinfectant solution, EDS) and application at a water treatment plant. The study compares the Cl 2 gas and EDS systems over 36 months, with 18 months for Cl 2 gas and, after the implementation, 18 months for the EDS system (12-month dry season and 6-month wet season). Turbidity, residual Cl 2 , pH, total and faecal coliforms and DBPs were monitored. Turbidity was within legal limits and DBPs below both legal limits and limits of detection. For Cl 2 gas, residual Cl 2 suffered a decrease in wet and dry periods. However, the EDS maintained residual Cl 2 to the network tips without significant variations, with operational costs reduced by $41%.The study demonstrates that on-site Cl 2 generation can be employed for water disinfection for large urban areas with considerable economic and technical advantages. K E Y W O R D S chlorine gas, disinfection, electrochemical disinfectant solution, urban water treatment, water treatment plant 1 | INTRODUCTION An important factor in sanitation policy is the handling of water for human consumption, ranging from collection, treatment and storage to distribution. The most used products for disinfection are chlorine based, such as chlorine dioxide (ClO 2 ), various hypochlorite (ClO À ) forms and chlorine gas (Cl 2 ) itself (Abdullah et al., 2009). Chlorine for disinfection of drinking water has been widely used for more than 100 years, because it is low cost and presents residual disinfection capacity in the distribution systems, whereas other agents, such as ozone (O 3 ) or hydrogen peroxide (H 2 O 2 ), do not present this capacity (Abdullah et al., 2009) and can also form toxic degradation byproducts (Ike, Lee, & Hur, 2019).Researchers have observed that disinfectant stability (concentration) in distribution network can depend on several factors, including line pressure, water quality, mains maintenance and disinfectant type (Blokker, Smeets, & Medema, 2014). In the case of Cl 2 in the distribution network, it has been observed that concentration decreases with distance from the original dosage point (Angulo et al., 2017). Therefore, at the exit point of the water treatment plant (WTP), the concentration is generally higher than at the extremes of the distribution system, as seen in the literature (Angulo, 2017;Fisher, Kastl, & Sathasivan, 2011). It has been reported that maintenance in the distribution system, during pipe opening, removal and substitution, may contribute to drinking water contamination by pathogens by permitting the entrance of contaminated materials (Blokker et al., 2014).
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