Oxidation-reduction Potential Levels Research Articles

Effects of insufficient air injection on methanogenic Archaea in landfill bioreactor

In this study, methanogenic Archaea diversity in an aerated landfill bioreactor filled with co-disposed incineration bottom ashes and shredded incombustible wastes was monitored and analyzed as a function of time using molecular techniques. Besides, the effects of insufficient air injection on the bioreactor performance and methanogenic diversity were evaluated thoroughly. Results indicated that rapid bio-stabilization of solid waste are possible with aerated landfill bioreactor at various oxygen and oxidation reduction potential levels. Slot-blot hybridization results of leachate samples collected from aerated landfill bioreactor showed that archaeal and bacterial activities increased as stabilization accelerated and bacterial populations constituted almost 95% of all microorganisms. The results of slot-blot hybridization and phylogenetic analysis based on 16S rRNA gene revealed that Methanobacteriales and Methanomicrobiales were dominant species at the beginning while substituted by Methanosarcina-related methanogens close to the end of the operation of bioreactor.

(69) Use of Hypochlorous Acid for Treatment of Greenhouse Irrigation Water

Scaling from dissolved and suspended solids in irrigation water reduces the efficiency of greenhouse irrigation systems. Water deposits inside pipes reduce water flow and deposits may reduce the flow through irrigation emitters, often clogging them. If not properly maintained, the clogging of emitters requires constant maintenance. This results in considerable labor expense and/or emitter replacement. Scaling inside irrigation system pipes also has the potential to harbor plant pathogens from the resulting biofilms. Oxcide, a novel hypochlorous acid (HOCl) compound, is produced electrochemically by removing sodium and hydroxide from sodium hypochlorite. The elimination of sodium hydroxide from the product creates a nontoxic oxidizer. A system to inject Oxcide into irrigation water at a commercial Colorado greenhouse was installed to maintain irrigation efficiency of emitters and irrigation lines during Winter 2003. The oxidation reduction potential (ORP) was monitored and visual evaluations of irrigation equipment in the Oxcide treated zones compared to those zones not treated with Oxcide was conducted. During January through March, geranium stock plants were irrigated with water that maintained ORP levels at around 600 mV. Visual ratings of the irrigation emitters revealed that the injection of Oxcide in the irrigation water did reduce the level of deposition. Deposition on the main feed lines was so thick that they hindered the complete closure of existing valves. Treatment of the irrigation water Oxcide injection for six months successfully removed of the scale and deposits from the water line.

Effect of low ORP in anoxic sludge zone on excess sludge production in oxic-settling-anoxic activated sludge process

This paper studied the effect of oxidation–reduction potential (ORP) in the anoxic sludge zone on the excess sludge production in the oxic-settling-anoxic process (OSA process), a modified activated sludge process. Two pilot-scale activated sludge systems were employed in this study: (1) an OSA process that was modified from a conventional activated sludge process by inserting a sludge holding tank or namely the “anoxic” tank in the sludge return line; and (2) a conventional process used as the reference system. Each was composed of a membrane bioreactor to serve the aeration tank and solid/liquid separator. Both systems were operated with synthetic wastewater for 9 months. During the operation, the OSA system was operated with different ORP levels (+100 to −250 mV) in its anoxic tank. It has been confirmed that the OSA system produced much less excess sludge than the reference system. A lower ORP level than +100 mV in the anoxic tank is in favor of the excess sludge reduction. When the ORP level decreased from +100 to −250 mV the sludge reduction efficiency was increased from 23% to 58%. It has also been found that the OSA system performed better than the reference system with respect to the chemical oxygen demand removal efficiency and sludge settleability. The OSA process may present a potential low-cost solution to the excess sludge problem in an activated sludge process because addition of a sludge holding tank is only needed.

Water Desirable for the Human Body in Terms of Oxidation‐Reduction Potential (ORP) to pH Relationship

ABSTRACT: The relationships between ORP (oxidation‐reduction potential) and pH were measured using samples of blood plasma, amniotic fluid, saliva, urine, vegetables, fruits, livestock products, fishery products, and various kinds of commercial beverages. It was found that these samples were in the reduction system region with respect to the equilibrium ORP level, which signifies that plants and animals, including human beings, have a reductive characteristic in terms of ORP. Here we propose that a conceptual kind of water having a reductive characteristic in terms of ORP and a pH value ranging from weak acidity to weak alkalinity can be categorized as “Vital Water”, which is analogous to human body fluid.

Variation of Oxidation–Reduction Potential Along the Breakpoint Curves in Low‐Ammonia Effluents

This study was part of an integrated series of investigations conducted at the 6.6 m3/s (150 mgd) City of Phoenix, Arizona, 91st Avenue Wastewater Treatment Plant to improve the chlorination system and optimize chlorine use after the plant was converted to a nitrification– denitrification (NdeN) plant. The objective of this study was to evaluate chlorine breakpoint behavior and assess oxidation–reduction potential (ORP) with different regimes of the breakpoint curve to reflect ORP behavior in a mixed oxidant and reductant environment typical of a chlorine disinfection system in an NdeN plant. The information was also useful for confirming the results of earlier studies on the fate of nitrite‐nitrogen (NO2−–N) in chlorine reactions, the phenomenon of microbreakpoint formation, and the relative competition for chlorine between ammonia and organics and between ammonia and other inorganics including NO2−–N. Laboratory analysis included measurement of the chlorine species (free chlorine and mono‐, di‐, and trichloramines) and NO2−–N, nitrate‐nitrogen, ammonia, pH, dissolved oxygen, and ORP in low‐ammonia effluents (effluents spiked with various amounts of ammonia) after addition of various chlorine doses. The study indicated that the overall shape of ORP curves follows the pattern of the breakpoint curves. However, the ORP curves were relatively flat at the monochloramine hump region of the curve. Also, ORP increased sharply at the beginning of the monochloramine region and at the beginning of the free chlorine region. The ORP curves eventually flattened again after the initial steep rise. Thus, at the flat portions of the curve, a marginal advantage could be derived with further increases in chlorine dose, and contact time becomes a critical factor in disinfection efficiency. A dip in the ORP curve was invariably observed at the breakpoint even though the dip was of a lesser degree than that of the residual curve. Greater concentrations of dichloramine (which have a greater ORP than monochloramine) expected at the downswing of the breakpoint curve could not sustain the maximum ORP levels observed at the monochloramine region. This suggested that organochloramines may also be a factor in the ORP dip at the breakpoint. Finally, ORP did not vary in direct proportion to total chlorine residual or in direct proportion to the concentration of individual chlorine residual species. Implications of these results are comparatively discussed with reference to the two methods of chlorination control: chlorine‐residual‐based control and ORP‐based control.

Controlling factors for simultaneous nitrification and denitrification in a two-stage intermittent aeration process treating domestic sewage

This bench-scale research investigated the controlling factors for simultaneous nitrification and denitrification (SND) in a 2-stage, intermittent aeration (IA) process, designed for nitrogen and phosphorus removal. The 2-stage process consisted of an anaerobic zone followed by an oxidation–reduction potential (ORP) controlled, intermittently aerated, completely mixed (IACM), tank. The three independent variables examined were the average ORP level, organic substrate (acetate and methanol) dosage and aeration cycle. The sewage used was completely of residential origin. Nitrogen balance clearly indicated that the nitrogen loss, due to SND in the aeration tank, contributed 10% to 50% of the influent TKN to the overall nitrogen removal. Significant differences in both nitrification and denitrification in the IACM tank were observed, when different average ORP levels were applied to the aeration control; this proved that absolute ORP can be used as a real-time control parameter for SND. Under low DO and intermittent aeration conditions, acetate and methanol additions improved nitrification over the entire dosage range and denitrification at relatively low dosages. Finally, a longer aeration cycle, with a zero-DO period, appeared to favor sequential nitrification and denitrification (SQND), not SND.

Asporogenic anaerobic thoracic empyema--an experimental model for anaerobic thoracic empyema in rabbits

Sterile pleural effusion was induced by intrapleural administration of turpentine, and empyema was induced by direct intrapleural inoculation of bacteria in rabbits. Experimental models of anaerobic thoracic empyema were successfully made in this study, using Escherichia coli, Peptostreptococcus asaccharolyticus, Bacteroides fragilis, using the following methods; (1) a single bacterium inoculation of, a) E. coli, b) P. asaccharolyticus, c) B. fragilis, (2) simultaneous inoculations with an aerobe and an anaerobe, a) E. coli + P. asaccharolyticus, b) E. coli + B. fragilis. (3) an anaerobic inoculation 5 days after an aerobic inoculation, a) P. asaccharolyticus inoculation 5 days after E. coli inoculation, b) B. fragilis inoculation 5 days after E. coli inoculation. The developments of several parameters (sialic acid levels, glucose levels, oxidation-reduction potential levels, bacterial counts and WBC counts in the pleural fluid and so on) were measured in each group. There was little difference of the rate of incidence of empyema between each group. Empyema was highly induced even by a single anaerobe inoculation. The following tendencies were observed in development of parameters: (1) sialic acid levels and oxidation-reduction potential levels were decreased only in the conditions being associated by B. fragilis infections. (2) in mixed infections of E. coli and anaerobes, bacterial counts of E. coli increased in number in the late phases of the infections probably by the influences of anaerobes. The experiments of groups (2) and (3) were designed for demonstrations of biphasic infections between aerobes and anaerobes, but it turned out that quite unexpected results were seen in these models.

Oxidation-reduction potential and concomitant growth patterns of cultures of Earle's "L" cells in centrifuge bottle spinners.

AbstractPrevious studies of oxidation‐reduction potential (ORP) variation in monolayer (Roux bottle) cultures pointed out the need for data on pH and ORP patterns in simple spinner cultures. This information was desirable for optimizing conditions of growth in small 1‐L and New Brunswick fermentors. Results of experiments in 250‐ml centrifuge spinner vessels are presented showing that incubation of media prior to inoculation induces desirable qualities reflected in better growth. The importance of initial ORP values of the medium is discussed. The relationship of ORP levels to yield and longevity of cell growth is also considered. The ORP level of the medium at inoculation is shown to be effected by previous incubation.

The relationship of oxidation‐reduction potential to the growth performance of tissue culture media poised prior to incubation

AbstractEarlier observations revealed that incubation of media and the attendant changes in oxidation‐reduction potential (ORP) were related to improved cell production. This is a report, of work done to show that the higher levels and increased rates of growth of cells grown in incubated medium are associated with the ORP level of the medium before inoculation of the medium with cells. Work was done using 250‐ml centrifuge spinner bottles as the culture vessels. Further work is needed to establish the desirability of deliberate poising of media prior to use for studies in small vessels and flasks.