Madars Reimanis

Disinfection effect of electrochemically generated chlorine on surface associated Escherichia coli in a drinking water system

AbstractFor many years, electrochemical treatment has been proposed as a potential alternative to conventional drinking water chlorination due to its simplicity, ease of use and ability to generate active disinfectant from ions naturally found in the drinking water The aim of this study was to evaluate the survival of Escherichia coli on the surfaces of water distribution system after exposure to in situ electrochemically generated chlorine. To analyse the effect of chlorine and its reaction intermediates, completely mixed reactor with or without ingenuous biofilm was supplied with natural drinking water containing low amount of chloride ions (<10 mg/L) and treated with non-stoichiometric titanium oxide electrodes (TiO2−x) at low current density (4.1–8 mA/cm2) which generate predominantly chlorine species. Various cell viability markers (cultivability, ability to divide as such and respiratory activity) were assessed in this study. The results showed that electrochemical disinfection was very effective to...

Drinking Water Disinfection with Electrolysis

Nowadays electrochemical disinfection has gained an increasing attention as an alternative to conventional drinking water disinfection, since it is regarded as environmentally friendly, amendable to automation, inexpensive, easily operated and is known to inactivate a wide variety of microorganisms from bacteria to viruses and algae. We found that along with increasing the number of electrodes in our equipment from 2 to 24, the resistance of chlorine-generating electrolytic cell and specific work of electric current decreased. During the electrolysis the amount of generated Cl2 increased along with the increase of chloride ion concentration in the solution and the intensity of electric current. The technological process parameters (flow rate, current intensity) have been established to obtain a predetermined amount of generated chlorine during the electrolysis process. A comparison of flow and circulating (3 times) regimes for electrolysis of tap water with chloride ion concentration below 10 mg/L showed that circulation is necessary to generate active chlorine (above 1 mg/L). At the same time, when no circulation was performed, even a 0.9 A treatment was not enough to generate detectable levels of free chlorine. Electrochemical disinfection of tap water with non-stoichiometric titanium oxide electrodes was effective enough to inactivate both metabolically active and cultivable bacteria E. coli to undetectable levels within 15 minutes at 0.5 A current intensity. Mūsdienās ūdens elektroķīmiskajai dezinfekcijai, kā alternatīvai tradicionālajām dezinfekcijas metodēm, tiek pievērsta liela uzmanība, jo tā ir videi draudzīga, viegli automatizējama, salīdzinoši lēta, viegli vadāma un ir zināma tās dezinficējošā iedarbība uz plašu mikroorganismu klāstu - no baktērijām līdz vīrusiem un aļģēm. Eksperimentāli konstatēts, ka, palielinot elektrodu skaitu elektrolīzes iekārtā no 2 līdz 24, tās pretestība un strāvas īpatnējais darbs samazinājās. Izdalītā Cl2 daudzums elektrolīzes laikā palielinājās, palielinoties hlorīda jonu koncentrācijai šķīdumā un elektriskās strāvas stiprumam. Variējot elektrolīzes procesa tehnoloģiskos parametrus (ūdens plūsmas ātrumu, strāvas stiprumu), iespējams sasniegt noteiktu izdalītā hlora daudzumu. Salīdzinot ūdens, kurš satur hlorīda jonus mazāk par 10 mg/L, apstrādi ar elektrolīzi caurplūdes režīmā ar cirkulācijas režīmu (3 reizes), konstatēts, ka ūdens apstrādi vēlams veikt cirkulācijas režīmā, lai būtu iespējams saražot vairāk aktīvā hlora (koncentrācijā, lielākā par 1 mg/L). Noteikts, ka process, veicot ūdens apstrādi ar elektrolīzi caurplūdes režīmā pat, ja strāvas stiprums 0,9 A, nenodrošināja aktīvā hlora veidošanos detektējamos daudzumos. Elektroķīmiskā dezinfekcija, izmantojot nestehiometriskā titāna oksīda elektrodus, bija pietiekami efektīva, lai pilnībā inaktivētu metaboliski aktīvās un kultivējamās E. coli baktērijas 15 minūšu laikā, ja strāvas stiprums 0,5 A.

INFLUENCE OF VARIOUS PHYSICAL-CHEMICAL TREATMENT METHODS ON MICROBIAL GROWTH IN WATER

Use of the TinO2n-1 electrode for water electrolysis process promotes the destruction of organic matter as shown by the changes in permanganate index different values of electrolysed and non electrolysed solution. Using the TinO2n-1 electrode in the electrolysis process with the presence of chlorine and bromine ions can create a lasting disinfectant effect that was demonstrated by the sharp decrease in the number of bacterial colony forming units in electrolysed solutions. Using the TinO2n-1 electrode in the electrolysis process with the presence of iodine ions can create a bacteriostatic effect which was maintained for at least 10 days in electrolysed solutions

Electrochemical Studies of Nonstoichiometric TiO2-x Ceramic

TiO2 ceramic was prepared using extrusion technology and thermal treatment in two stages: sintering in air and subsequent annealing under high vacuum conditions. Sample thermal treatment in high vacuum conditions causes formation of nonstoichiometric titanium oxide ceramic. As a result electrical conductivity of the material significantly increases. Such a material can be used for electrode production for electrochemical water treatment.