Cleaning Reagent Research Articles

Potential degrading effect of sodium hypochlorite on exhibits containing DNA

The use of a sodium hypochlorite solution as a cleaning reagent is common practice among many laboratories for contamination minimisation purposes. Whilst its effectiveness in the decontamination of tools and surfaces has been verified at specific concentrations, it has not yet been established whether any residual sodium hypochlorite potentially remaining on tools/surfaces following cleaning has a detrimental effect if direct contact is made with an exhibit containing DNA. To investigate the effect of residual hypochlorite, surfaces were treated with 10% hypochlorite (air-dried or wiped dry), 1% hypochlorite (air-dried or wiped dry), or 1% hypochlorite (wiped dry) followed by the application of water (wiped dry). Treated surfaces came into contact with surfaces carrying 200ng of DNA within 100μL, or 20ng within 20μL. To observe the potential degrading effects of sodium hypochlorite, the quantity and quality of DNA within DNA deposits following contact with treated and untreated surfaces were compared. Overall, no degrading effect on DNA quantity/quality was observed, with the exception of DNA deposits that came into contact with surfaces treated with 10% hypochlorite and air-dried. It is therefore recommended that surfaces cleaned with high concentrations of hypochlorite be wiped dry or rinsed with an appropriate agent (water) following application.

N-nitrosamine rejection by reverse osmosis: Effects of membrane exposure to chemical cleaning reagents

The impact of chemical cleaning on the removal of N-nitrosamines by low pressure reverse osmosis (RO) membranes was investigated. The results show that caustic chemical cleaning resulted in an increase in membrane permeability but caused a notable decrease in the rejection of N-nitrosamines. The impact of caustic chemical cleaning was particularly obvious for N-nitrosodimethylamine (NDMA) and N-nitrosomethylethylamine (NMEA), which have the lowest molecular weight amongst the N-nitrosamines investigated in this study. A correlation between the increase in permeability and the decrease in the rejection of either NDMA or NMEA could be observed. The rejection of conductivity also decreased as the membrane permeability increased, indicating that conductivity rejection can be an indicative parameter of predicting changes in NDMA and NMEA rejection during RO plant operation. The impact of caustic cleaning was not permanent and could be significantly reduced by a subsequent acidic cleaning step.

Influence of formulated chemical cleaning reagents on the surface properties and separation efficiency of nanofiltrationmembranes

This study investigated the impact of two caustic and one acidic cleaning formulations (namely MC11, PC98, and MC3, respectively) on the properties and separation efficiency of three different nanofiltration (NF) membranes (namely NF270, NF90 and TFC-SR100). Overall, the impact of chemical cleaning on surface properties and rejection was membrane and cleaning reagent specific. It was driven mostly by conformational changes of the membrane polymeric active skin layer in response to an extreme caustic or acidic environment and to a certain extent by the adsorption of cleaning additives (e.g., surfactants and chelating reagents). The influence of chemical cleaning on the membrane properties and separation efficiency was most severe for the NF270 due to its loose and very thin active skin layer. Caustic cleaning using either the MC11 or PC98 formulations led to a significant increase in the permeability and a considerable decrease in the rejection of both inorganic salts and trace organic contaminants by the NF270 membrane. In contrast, acidic cleaning using the MC3 formulation caused a small decrease in the permeability of the NF270 membrane. The influence of chemical cleaning on the NF90 and TFC-SR100 membranes was much less significant, possibly because of their thicker and denser active skin layer. The results reported here demonstrated that the impact of chemical cleaning was not permanent and could be minimised by adapting an appropriate strategy involving caustic cleaning followed by acidic cleaning. FTIR analyses of the virgin and cleaned membranes showed no discernible impact of chemical cleaning on the bonding structure of all three membranes investigatedhere.

Comparison of chemical cleaning reagents and characterization of foulants of nanofiltration membranes used in surface water treatment

Fouling continues to be an important limitation in membrane operation for water treatment. In this work, we compare various chemical agents with respect to their ability to remove fouling as well as their potential to deteriorate membrane rejection or the physical properties of the membrane. Contact angle of the membrane surface appears to be a good indicator of the efficiency of the membrane cleaning in parallel with results of the total organic carbon and the metal presence. The specific ultraviolet absorbance (SUVA) is also shown to be a useful parameter for monitoring the efficiency of cleaning, that can easily be implemented in-line on a full-scale facility.

Optimisation of MF membrane cleaning protocol in an Indirect Potable Reuse (IPR) scheme

The control of fouling in a microfiltration process dedicated to wastewater reuse demands an adequate chemical cleaning procedure. A study has been conducted to optimise this using Box–Behnken design (BBD) associated with multiple linear regression. Bench-scale modules, formed with hollow fibre membrane fouled through use on a pilot plant, were employed to assess the cleaning efficiency. Parameters studied were chemical type (oxidising, alkaline and acidic), reagent concentration, cleaning temperature and soak time. Oxidising reagents were found the most efficient followed by alkali and acid reagents. NaOCl at pH 10 was the most efficient cleaning reagent allowing 100% permeability recovery. An envelope of optimum parameters was defined from the bench scale study for this reagent. The model was found to accurately represent the plant performance for permeability measurements conducted at the same temperature on the bench-scale as that for plant operation. The effect and significance of the parameters were found to vary from one reagent to another one, underlining the importance of the assessing the entire parameter value range and the benefit offered by BBD for carrying out this efficiently with the fewest number of experiments.

Membrane life estimation in full-scale immersed membrane bioreactors

Limited quantitative available information exists regarding the robustness of membranes used in immersed membrane bioreactor (iMBR) applications, and no information on the relative contribution of the two main membrane failure modes of permeability and integrity loss. Such information is crucial given the significance of membrane replacement costs to the viability and sustainability of iMBRs. Measurements of membrane permeability and integrity have been made on flat sheet (FS) membrane cartridges sampled from six existing full-scale iMBRs. The recovered membrane permeability (i.e. the permeability recorded following chemical cleaning) revealed all plants operating for less than six years to have a clean water flux greater than that of the virgin membrane cartridge. A lower permeability was recorded only for the oldest plant (eight years of operation), and this was attributed to high levels of phosphate scale fouling. Assigning a linear trend between membrane permeability loss and operation time indicated the recovered membrane permeability to reach a threshold minimum value for virgin membrane cartridge after ∼7 years of operation. The membrane cartridge integrity, as measured by the strength of the weld at its perimeter, correlated with the total volume of water permeated per cartridge, the total weight of NaOCl cleaning reagent to which the panel has been exposed, and the mean volume of water permeated per cartridge between chemical cleans. In this case, the linear trend indicated a membrane life equating to ∼900 m 3 per panel or exposure to a total of 1.3 kg NaOCl before the threshold minimum welding strength for membrane cartridge was reached. As with the permeability data, only for the oldest plant was the measured mean membrane integrity below the threshold. The data indicate membrane life for FS iMBRs to exceed six years, on the basis of both permeability and integrity, and may ultimately be limited only by the irreversible deposition of inorganic scale, rather than operation time.

Cleaning Small-Volume Nebulizers

Aerosol inhalation is an important treatment for immobilized patients living at home. Aerosol application of medicine can reduce symptoms of acute and chronic respiratory tract diseases. However, aerosol therapy performed using small-volume nebulizers (SVNs) may induce bacterial colonization and increase pneumonia risk. The proper cleaning of SVNs is important to prevent pneumonia. This experimental study was designed to compare the cleaning efficacy of two different cleaning reagents and three different cleaning methods with regard to SVNs. Tap water and sterile distilled water were used as the two cleaning reagents. The three different cleaning methods included (a) soaking the nebulizer for 10 minutes, (b) rinsing the nebulizer for 30 seconds, and (c) soaking the nebulizer for 10 minutes, changing the water, and then rinsing reagent for 30 seconds. There were 13 groups in the study. Six groups were assigned into the noncontaminated and the remaining seven were contaminated with Escherichia coli. One contaminated group was assigned with noncleaning as a positive control group, and 12 groups were assigned into each of the unique cleaning reagent + cleaning method combinations. Evaluations of microbe presence were performed by taking samples from nebulizers after cleaning. Results showed insignificant differences among cleaning reagent efficacies (p = .186) and significant differences among cleaning methods (p < .001). The soak-then-rinse method was found to provide significantly better results in comparison with the other two methods. On the basis of the results, we suggest that SVN cleaning procedures should focus on the cleansing method. Findings provide evidence to support that the soak-then-rinse method may the preferred technique to use in cleaning SVNs.

The Effect of Cleaning Agents on the Ability to Obtain DNA Profiles Using the Identifiler™ and PowerPlex® Y Multiplex Kits

A year after the introduction of Identifiler™ into the forensic DNA laboratories of the Institute of Environmental Science and Research Limited (ESR), increasing occurrences of dropout of the three loci, D7S820, D18S51, and FGA, were observed in samples where the DNA was not degraded and sufficient DNA was present that full DNA profiles were to be expected. The dropout was either partial or complete at these loci. Full profiles could sometimes be obtained by reamplification of samples using the same input amount of DNA. After a thorough investigation of the methods and procedures used in the laboratory, the cause of this inhibition was identified as the cleaning agent TriGene™ ADVANCE. This was determined after the deliberate addition of varying amounts of different cleaning reagents into the DNA amplification reactions. At concentrations of 0.004% TriGene™ ADVANCE caused inhibition resulting in tri-loci dropout. At concentrations of 0.04% and higher, complete inhibition was observed. An effect was also seen on the amplification of samples using the Y STR profiling system PowerPlex(®) Y. This work highlights the importance of checking all reagents and chemicals prior to use, even those with no apparent direct influence on the DNA profiling process.

Gypsum Scaling and Cleaning in Forward Osmosis: Measurements and Mechanisms

This study investigates gypsum scaling and cleaning behavior in forward osmosis (FO). The results show that gypsum scaling in FO is almost fully reversible, with more than 96% recovery of permeate water flux following a water rinse without addition of chemical cleaning reagents. Parallel comparisons of fouling and cleaning were made between FO (without hydraulic pressure) and RO (under high hydraulic pressure) modes. The shape of the water flux decline curves during gypsum scaling is similar in the two modes, but the flux recovery in FO mode is higher than that in RO mode by about 10%. This behavior suggests that operating in FO mode may reduce the need for chemical cleaning. The role of membrane materials in controlling gypsum scaling and cleaning was investigated using cellulose acetate (CA) and polyamide (PA) membranes. Gypsum scaling of PA membranes causes more severe flux decline and is harder to clean than that of CA membranes. AFM force measurements were performed between a gypsum particle probe and the membrane surfaces to elucidate gypsum scaling mechanisms. Analysis of adhesion force data indicates that gypsum scaling of the PA membrane is dominated by heterogeneous/surface crystallization, while gypsum scaling of the CA membrane is dominated by bulk crystallization and subsequent particle deposition.This finding implies that membrane surface modification and new material development can be an effective strategy to mitigate membrane scaling.

Organic fouling of forward osmosis membranes: Fouling reversibility and cleaning without chemical reagents

The recently resurgent forward osmosis (FO) membrane process has the potential to become a sustainable alternative to conventional membrane processes. However, the fouling and cleaning behavior of FO membranes remains largely unknown. There is a need to fully understand the fouling phenomena in FO in order to take advantage of this emerging technology. In this study, we used alginate as a model organic foulant to examine FO membrane fouling and cleaning behavior with the ultimate goal of determining the underlying FO fouling/cleaning mechanisms. Results showed that alginate fouling in FO is almost fully reversible, with more than 98% recovery of permeate water flux possible after a simple water rinse without any chemical cleaning reagents. We also studied the role of applied hydraulic pressure in membrane fouling and cleaning by performing fouling tests in FO (without hydraulic pressure) and RO (with hydraulic pressure) modes. Flux recovery in the FO mode was much higher than that in the RO mode under similar cleaning conditions, although the rate of membrane flux decline was similar in the two modes. The fouling reversibility of FO was attributed to the less compact organic fouling layer formed in FO mode due to the lack of hydraulic pressure. Our results suggest that operating in FO mode may offer an unprecedented advantage in reducing or even eliminating the need for chemical cleaning. AFM force measurements were used to elucidate the impact of membrane materials (cellulose acetate versus polyamide) on membrane fouling and cleaning behavior. Adhesion force data revealed that a small percentage of relatively adhesive sites on the membrane surface play an important role in increasing membrane fouling potential and decreasing cleaning efficiency. This finding implies that using average adhesion force to predict membrane fouling potential is inadequate. Extensive long-range adhesion forces are observed for the polyamide membrane in the presence of alginate and calcium ions. The long-range interactions are attributed to calcium bridging of alginate molecules between the AFM probe and the adhesive sites on the polyamide membrane surface.

The substitution of sand filtration by immersed-UF for surface water treatment: pilot-scale studies

The newly issued National Drinking Water Standard required that turbidity should be lower than 1 NTU, and the substitution of sand filtration by immersed ultrafiltration (immersed-UF) is feasible to achieve the standard. This study aimed to optimise the operational processes (i.e. aeration, backwashing) through pilot scale studies, to control membrane fouling while treating the sedimentation effluent. Results indicated that the immersed-UF was promising to treat the sedimentation effluent. The turbidity was below 0.10 NTU, bacteria and E. coli were not detected in the permeate water. The intermittent filtration with aeration is beneficial to inhibit membrane fouling. The critical aeration intensity is observed to be 60.0 m(3) m(-2) h(-1). At this aeration intensity, the decline rate of permeate flux in one period of backwashing was 1.94% and 7.03% for intermittent filtration and sustained filtration respectively. The different membrane backwashing methods (i.e. aeration 1.5 min, synchronous aeration and water backwashing 2 min, water backwashing 1.5 min; synchronous aeration and water backwashing 3 min, water backwashing 2 min; aeration 3 min, single water backwashing 2 min; synchronous aeration and water backwashing 5 min; single water backwashing 5 min) on the recovery of permeate flux were compared, indicating that the synchronous aeration and water backwashing exhibited best potential for permeate flux recovery. The optimal intensity of water backwashing is shown to be 90.0 L m(-2) h(-1). When the actual water intensity was below or exceeded the value, the recovery rate of permeate flux would be reduced. Additionally, the average operating cost for the immersed UF membrane, including the power, the chemical cleaning reagents, and membrane modules replacement, was about 0.31 RMB/m(3).

Fast, broad-range disinfection of bacteria, fungi, viruses and prions

Effective disinfectants are of key importance for the safe handling and reprocessing of surgical instruments. This study tested whether new formulations containing SDS, NaOH and 1-propanol (n-propanol) are simultaneously active against a broad range of pathogens including bacteria, fungi, non-enveloped viruses and prions. Inactivation and disinfection were examined in suspension and on carriers, using coagulated blood or brain homogenate as an organic contaminant. Coomassie blue staining was used to assess whether the formulations undesirably fixed proteins to rough surfaces. A mixture of 0.2 % SDS and 0.3 % NaOH in 20 % n-propanol achieved potent decontamination of steel carriers contaminated with PrP(TSE), the biochemical marker for prion infectivity, from 263K scrapie hamsters or from patients with sporadic or variant Creutzfeldt-Jakob disease. 263K scrapie infectivity on carriers was decreased by > or =5.5 logs. Furthermore, the formulation effectively inactivated poliovirus, hepatitis A virus and caliciviruses (including murine norovirus) in suspension tests. It also yielded significant titre reductions of bacteria (Enterococcus faecium, Mycobacterium avium; >6 logs), fungi (spores of Aspergillus niger; > or =5 logs) and poliovirus (>4 logs) embedded in coagulated blood on carriers. The formulation was not found to fix proteins more than was observed with water as the cleaning reagent. In conclusion, SDS, NaOH and n-propanol can synergistically achieve fast, broad-range disinfection.

Study on Fouling and Cleaning of PVDF Membrane

The effects of different water sources on the fouling of PVDF membrane are different. On the basis of the scientific appraisal, the correct cleaning process and cleaning reagent are selected to recover the flux and other performances of PVDF membrane. The results indicate that the TMP (transmembrane pressure) of PVDF membrane can be effectively recovered by CIP (clean-in-place) process, and almost reaches the initial level even under the circumstance that PVDF membrane has been used for a certain time and its TMP can not be recovered by either physical cleaning process or CEB (chemically enhanced backwashes).

In the search of alternative cleaning solutions for MBR plants

The objective of the study was to identify alternative cleaning reagents to chlorine for membrane permeability regeneration in MBR applications. Indeed, chlorine is prohibited in some countries because of the formation of by-products such as THM. The study was focused on the comparison of ten cleaning reagents performances and in particular on their ability to remove irreversible fouling. The tests were carried on with the A3 Water Solutions' Maxflow membrane (flat sheet membrane). A specific experimental protocol was defined at lab scale to develop an irreversible fouling by filtering sludge supernatant. The more promising reagents at lab scale were then tested on the A3 membrane continuously immersed in a MBR pilot plant functioning under typical biological conditions (MLSS=11 g/l; SRT=28 days). A full scale test was finally performed with hydrogen peroxide, one of the best reagents. Chlorine was taken as reference for all performed tests. The cleaning performances of the selected reagents were different at the different scales, probably due to the difficulty to obtain an irreversible membrane fouling at larger scales. This testing procedure will be reproduced with other membrane materials to have a better understanding of interactions between irreversible fouling, material nature and chemical reagents.

AQUAPOT: study of several cleaning solutions to recover permeate flow in a humanitarian drinking water treatment facility based on spiral wound UF membrane. Preliminary test (I)

Access to safe drinkable water is a basic human right and an international goal. Since 1996, AQUAPOT international project, has researched and developed low cost, easy to use and effective water treatment technologies able to be used in developing countries. Recently, the project has carried out the design of three potabilization units based on membrane technology and its installation in rural areas of Ecuador with no access to safe water. Field experience has shown that maintenance and cleaning of spiral wound ultrafiltration membranes is not done properly what can reduce the membrane’s life due to biofilm growth. In a medium term, this growth would affect the quality and the volume of the pure water produced by the drinkable water treatment facility. An applied research has been initiated to study several cleaning solutions that allow to recover an optimum permeate flow. For the preliminary test, samples from UF membrane were used. Methodology includes static assays in which membrane’s samples were immersed in a cleaning solution for over 12 or 24h at a temperature of 25 to 40°C. The study has allowed to select the most effective membrane’s cleaning solutions and the optimum conditions for its application. In addition, the study has allowed to verify the efficiency of the cleaning reagent in a drinkable water treatment plant.

THE FOULING AND CLEANING OF ULTRAFILTRATION MEMBRANES DURING THE FILTRATION OF MODEL TEA COMPONENT SOLUTIONS

ABSTRACT Proteins and polyphenols are the principal fouling constituents in the ultrafiltration (UF) of black tea liquor. The aim of this study was to determine the relative importance of individual components in the fouling process, to investigate any synergetic interactions that were occurring and to compare the cleaning characteristics of different fouled membranes. A 30‐kD molecular weight cutoff polysulfone UF membrane in dead‐end mode was challenged with model solutions of tea components. Model solutions consisted of tea proteins, theaflavins (TFs), thearubigins and caffeine. Sodium hydroxide was used as a cleaning reagent. Permeate flux decline curves were presented for single components and mixtures. Individual component transfer fluxes and rejections were also presented. An unexpected finding was that protein in a mixture with TFs could permeate the membrane to a degree, while a protein solution in the absence of the polyphenol was completely rejected. The inspection of membranes fouled by different solutions revealed different foulant morphologies. Membrane cleaning with 0.2 wt % sodium hydroxide was generally found to be effective.

Studies on nanofiltration membrane fouling in the treatment of water solutions containing humic acids

A major factor limiting the use of nanofiltration (NF) in the water treatment process is membrane fouling by natural organic matter. Two NF membranes, Desal 5 DK and DL, which have different hydraulic permeabilities, were compared. Solution chemistries selected for this investigation were concentrated on the common salts found in a variety of wastewaters, including monovalent ions (Na +, Cl −), divalent hardness cations (Ca 2+, Mg 2+) and divalent anions (SO 2− 4). Results of fouling experiments with humic acids demonstrated that the condition of hydrodynamics and the chemical compositions of the feed solutions could significantly influence the fouling tendency. Higher crossflow velocity and lower initial flux mitigated accumulation of humic acid (HA) on the membrane to some extent. The adsorption of humic substances onto the membrane surface was markedly enhanced in the presence of divalent cations due to the formation of HA-complexed divalent cations. The experiment also indicated that the membrane surfaces preferred to adsorb divalent cations rather than divalent anions because the membrane had a negative charge in the higher pH range investigated. In addition, choosing a proper divalent cation chelating agent as a cleaning reagent, especially at basic conditions, can improve the membrane process by dissolving and removing the HA fouling substance.

Recovery of protein from poultry processing wastewater using membrane ultrafiltration

The feasibility of using ultrafiltration (UF) to recover protein from poultry processing wastewater (PPW) after primary treatment was investigated. By using polysulfone membrane with 30,000 molecular-weight-cut-off, almost all crude proteins in PPW were retained, subsequently reducing the chemical oxygen demand (COD) in the effluent to less than 200 mgL−1. Similar to the processing of proteinaceous materials, the average fluxes reached only 100 Lm−2h−1. By identifying the optimal values of key operation parameters, including pH, volumetric flow rate, and transmembrane pressure (6.74, 683 mLmin−1 and 14 psi, respectively) using response surface methodology (RSM), the flux was improved to higher than 200 Lm−2h−1. Although severe membrane fouling was still inevitable after processing, flushing the membrane with a cleaning reagent was found capable of effectively restoring membrane performance.

On-line preconcentration of phosphate onto molybdate form anion exchange column

In this paper, we describe an automated flow injection system for measuring the concentration of phosphate based on a fluorescence quenching reaction between Rhoadamine 6G and phosphomolybdate with a preconcentration column, which was packed with a molybdate-form ion exchange resin to collect and preconcentrate the phosphate in the sample solution. Rhodamine 6G was chosen because the reaction with phosphomolybdate was fast and did not require heat. For the construction of a stable flow injection system, an aqueous methanol solution was used as the cleaning reagent to overcome the precipitation of ion-associated complexes between Rhodamine 6G and phosphomolybdate or Rhodamine 6G and molybdate. For the preconcentration and collection of the phosphate ions in a water sample, a preconcentration column, which was packed with a molybdate-form ion exchange resin, was combined with the proposed flow injection system and applied to natural water samples containing low concentrations of phosphate.

Cleaning of stainless steel surfaces and oxide dissolution by malonic and oxalic acids

The effectiveness and materials compatibility of malonic acid as a decontamination and chemical cleaning reagent has been explored. Comparison with its homologous oxalic acid demonstrates that malonic acid is a milder reagent, that dissolves the oxide scales more slowly but at acceptable rates, and provides better conditions for base metal protection. The mechanism of attack of malonic acid onto magnetite involves an autocatalytic process, mediated by ferrous ions. The rate is extremely sensitive to the concentration of this ion, and therefore the solution redox potential indirectly determines the rate of attack.