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.

Pengaruh Sodium Hipoklorit dan Kalsium Hipoklorit terhadap Daya Hidup Leptospira Patogenik

Leptospirosis is still a health problem in the word. Leptospirosis can be transmitted to humans trough contact with environment infected with pathogenic Leptospira. Efforts to control pathogenic Leptospira in the environment can be done one of them by disinfecting. Effective desinfectants for the control of pathogenic Leptospira include the active ingredients Calcium hypochlorite 60% and Sodium hypochlorite 5,25%. This study aims to determine the effectiveness of Calcium hypochlorite 60% and Sodium hypochlorite 5,25% against the life power of pathogenic Leptospira. This research is a laboratory study with pure experimental design. Serovar of pathogenic Leptospira used is Leptospira icterohaemorrhagiae. Leptospira icterohaemorrhagiae desnsity used as much as 5.7 x 106 Leptospira/ml. The concentrations of desinfectans and bacteria are: 5 ppm, 50 ppm, 500 ppm, 1000 ppm, 2000 ppm, 5000 ppm, 10.000 ppm, and 25.000 ppm. Observations are made every ten minutes and twenty minutes with three repeats. The results showed that Leptospira icterohaemorrhagiae could not survive when tested on 60% calcium hypochlorite and 5.25% sodium hypochlorite, respectively, at a concentration of 2000 ppm and a concentration of 1000 ppm. Statistical results showed there was a significant difference in the concentration of each disinfectant active ingredient. Thus, a disinfectans of chlorine with the active ingredient Calcium hypochlorite 60% and Sodium hypochlorite 5,25% effectively affects the viability of the Leptospira icterohaemorrhagiae. Keywords : Sodium Hypochlorite, Calcium Hypochlorite, Leptospira, Disinfectant Abstrak Leptospirosis masih menjadi masalah kesehatan di dunia. Leptospirosis dapat menular ke manusia lewat kontak dengan lingkungan yang mengandung Leptospira patogenik. Upaya pengendalian Leptospira patogenik di lingkungan dapat dilakukan salah satunya dengan pemberian disinfektan. Disinfektan yang efektif untuk pengendalian Leptospira patogenik diantaranya adalah bahan aktif kalsium hipoklorit 60% dan sodium hipoklorit 5,25%. Penelitian ini bertujuan mengetahui efektivitas bahan aktif kalsium hipoklorit 60% dan sodium hipoklorit 5,25% terhadap daya hidup Leptospira patogenik. Penelitian ini merupakan penelitian skala laboratorium dengan rancangan eksperimental murni. Serovar Leptospira patogenik yang digunakan adalah Leptospira icterohaemorrhagiae. Kepadatan Leptospira icterohaemorrhagiae yang digunakan sebanyak 5,7 x 106 Leptospira/ml. Konsentrasi campuran disinfektan dan bakteri yaitu: 5 ppm, 50 ppm, 500 ppm, 1000 ppm, 2000 ppm, 5000 ppm, 10.000 ppm, dan 25.000 ppm. Pengamatan dilakukan tiap 10 menit dan 20 menit dengan tiga kali ulangan. Hasil penelitian menunjukkan Leptospira icterohaemorrhagiae tidak dapat hidup saat diujikan ke kalsium hipoklorit 60% dan sodium hipoklorit 5,25% berturut-turut pada konsentrasi 2000 ppm dan konsentrasi 1000 ppm. Hasil statistik menunjukkan ada perbedaan signifikan dari besaran konsentrasi masing-masing bahan aktif disinfektan. Dengan demikian, disinfektan klorin dengan bahan aktif calcium hypochlorite 60% dan sodium hypochlorite 5,25% efektif memengaruhi daya hidup Leptospira icterohaemorrhagiae. Kata kunci: Sodium hipoklorit, Kalsium hipoklorit, Leptospira, Disinfektan

Chlorine As a Disinfectant in Water Treatment

Disinfection of treated water is a necessary process. For this, chlorine and its products are widely used. During the treatment process, chlorine is added to drinking water as elemental chlorine, sodium hypochlorite solution or dry calcium hypochlorite. When applied to water, each of these forms “free chlorine”, which destroys pathogenic organisms. If adequate water treatment is not readily available, the impact on public health can be devastating. Worldwide, about 1.2 billion people lack access to safe drinking water, and about 2.4 billion people lack sanitation. As per WHO, 3.4 million people die from waterrelated diseases. Drinking water chlorination will remain a cornerstone of disinfection. This is because of the wide range of benefits provided by chlorine. However, alternative disinfectants including ozone and UV radiation are available, all disinfection methods have unique benefits, limitations and costs. So, an engineer has to consider all the pros and cons of a disinfectant method properly before deciding the one to adopt. Keywords: Disinfection, Gaseous Chlorination, Sodium Hypochlorite, Calcium Hypochlorite, Ultraviolet, Ozone, Chlorine dioxide

Research on in vitro haploidization of heterozygotic breeding lines of tomato (Solanum lycopersicum L.)

Experiments were made in order to examin the influence of various factors on the induction of androgenesis in heterozygous breeding material of tomato. The factors like: length of buds the manner of sterilization, type and the composition of induction media, genotype and thermal shock were included in conducted experiments. Most of all sterile cultures with the highest number of anther-derived callus were obtain by applying 2,5% calcium hypochlorite for 5 minutes. Anther-derived calli was obtained in 9 breeding lines from 18 used genotypes. The induction medium with the composition based on B5 medium with the addition of 750 mg L-1 calcium chloride and 100 g L-1 sucrose proved to be the best for inducing androgenesis. The addition of thidiazuron and NAA to this medium in the following season and silver nitrate in the other experiminet improved the efficiency of this process, which was depended on the genotype. Despite the lack of statistically significant differences, the highest number of anther-derived calli was obtained when anthers were cooled for 2 days in +4oC in the refrigerating chamber.

A Fuzzy MADM Approach for Selecting the Best Cyanide Removal Method from a Gold Mine Wastewater

The cyanidation process is the most common method applied for the extraction of gold and silver in the hydrometallurgy industry, in which, sodium cyanide is used as a leaching agent. Therefore, the wastewater of gold mines contains a wide variety of cyanide ions needing to be removed before these wastewaters can be discharged to the receiving environments. In this study, a fuzzy multi-attribute decision-making approach (Fuzzy Delphi AHP and Fuzzy TOPSIS) was used for selecting the best cyanide removal method from the wastewater of Muteh gold mine. According to the experts' opinion, three methods including calcium hypochlorite, hydrogen peroxide and sodium hypochlorite were selected as alternatives. Then, by introducing the criteria influencing decision making, including cyanide removal ability, cost of process, amount of material consumed, time, pH, ease of performance and safety, and performing separated experiments, the criteria for each of three methods were determined. Finally, sodium hypochlorite was proposed as the best method for eliminating cyanide from wastewater. It was found that the rank of methods was as sodium hypochlorite (0.517) > calcium hypochlorite (0.474) > hydrogen peroxide (0.463).