Intensive Cleaning Research Articles

Limitations for transferring lab-scale microfiltration results to large-scale membrane bioreactor (MBR) processes

Membrane bioreactor (MBR) processes for the treatment of municipal and industrial wastewater have been extensively investigated in the past years. For this purpose, synthetic model feeds containing dissolved macromolecules and/or suspended solids were used to allow for a stable and reproducible feed composition. Lab-scale setups equipped with single membrane filaments and pilot plants containing single-bundle configurations were applied. Despite the fact that numerous of the corresponding findings were successfully transferred to large-scale MBR processes, it is expected that the filterability of activated sludge differs significantly from that of common model substances. Moreover, phenomena linked to the highly complex multi-phase flow of liquid, suspended solids and dispersed air bubbles which physically interacts with the membrane filaments make downsizing difficult. Therefore, the overall objective of this study was to evaluate the transferability of lab-scale microfiltration results to large-scale MBR processes. Our investigations have shown that the rheology of a model feed containing silica particles is similar to that of activated sludge with MLSS⩽3.5g/L. A noticeable sub-critical fouling was observed, but was removable by an intensive chemical cleaning using sodium hypochlorite. Lower fouling rates when increasing the aeration frequency with the same net aeration rate were found for both single-fibre and single-bundle tests, but are more pronounced on the larger scale. A macroscopic circulation flow affects the filtration performance of full-scale MBRs, but is difficult to mimic on a smaller scale. Fibre motion enhances the filtration performance, but is insensitive to packing density variations for bundles of up to four filaments.

Effect of Time in Chemical Cleaning of Ultrafiltration Membranes

AbstractChemical cleaning of ultrafiltration membranes is often considered successful when the flux through a cleaned membrane is much higher than through a pristine one. Here, a novel definition of cleaning intensity is proposed as the product of the concentration of the cleaning agent and the cleaning time (Ct), and it is shown that Ct values between 0.5 and 1.0 g h L–1 are sufficient for effective cleaning. Experiments with PES‐30 and PVDF‐30 membranes fouled by bovine serum albumin and cleaned with surfactant, oxidant, and formulated cleaning agents demonstrate that a good cleaning should last for 10–20 min and restore the flux through a virgin membrane. More intensive cleaning increases the membrane hydrophilicity and the water flux, but soon causes more severe fouling and even membrane disintegration.

Application of luminescent ATP rapid checks at ready-to-eat foods producing plant

Bioluminescent ATP determination has been applied at a ready-to-eat meals producer plant as a screening tool to evaluate the cleaning procedures and identify possible sources of microbial contamination. Luminescent ATP test revealed the risk situations in few minutes, any time it was supposed useful, and on site. All data were confirmed by the plate count method and immediate interventions were undertaken in risk situations, concerning not perfectly cleaned surfaces and cross-contamination between the areas for different types of foods. Various departments have been checked: cold stores, raw food manipulation areas, kitchens, coolers, and packaging areas. Critical situations were revealed in the fresh foods cold storage areas, which were consequently treated by more intensive cleaning procedures, and the raw food manipulation areas, which were physically separated by walls, were more intensively cleaned with exchanges between the various areas strictly regulated. Intervention effectiveness was confirmed by repeated controls using portable ATP assay, since the evaluation of the relationship between CFU and RLU gave good results, with an r<sup>2</sup> value of 0.83.

Integrated control of Ephestia cautella (Walker) in a confectionary factory

In a confectionary factory, integrated pest-management techniques were used for 12 months. Ephestia cautella is the major pest in this industry. Its presence was monitored using pheromone traps and water traps. The most critical areas were identified and water traps were better at identifying these areas than pheromone traps. Intensive cleaning and structural improvements were carried out when necessary. Water traps have been used as a mass trapping system because they catch both males and females. Catches in water traps showed a decrease in population density after 8-9 months. In a confined area, a mating disruption system was applied to interfere with moth mating. Most females caught with water traps were mated, although in the area where mating disruption was applied, the percentage of unmated females was higher compared with areas where mating disruption was not used. Keywords : Integrated pest management, Mating disruption, Water trap, Almond moth, Pheromone.

Hydrogen peroxide vapor decontamination of an intensive care unit to remove environmental reservoirs of multidrug-resistant gram-negative rods during an outbreak

Multidrug-resistant gram-negative rods (MDR-GNR) are an increasing cause for concern in intensive care units (ICUs). We used hydrogen peroxide vapor (HPV) to decontaminate our entire ICU in an attempt to eradicate undetected environmental contamination during outbreaks of MDR-GNR. Surface sampling identified GNR, including MDR strains, on 10 (48%) of 21 areas cultured after intensive cleaning but before decontamination with HPV, and on no areas after HPV. No new cases of Acinetobacter were identified for approximately 3 months after HPV.

Improving environmental hygiene in 27 intensive care units to decrease multidrug-resistant bacterial transmission*

To determine the thoroughness of terminal disinfection and cleaning of patient rooms in hospital intensive care units and to assess the value of a structured intervention program to improve the quality of cleaning as a means of reducing environmental transmission of multidrug-resistant organisms within the intensive care unit. Prospective, multicenter, and pre- and postinterventional study. Intensive care unit rooms in 27 acute care hospitals. Hospitals ranged in size from 25 beds to 709 beds (mean, 206 beds). A fluorescent targeting method was used to objectively evaluate the thoroughness of terminal room cleaning before and after structured educational, procedural, and administrative interventions. Systematic covert monitoring was performed by infection control personnel to assure accuracy and lack of bias. In total, 3532 environmental surfaces (14 standardized objects) were assessed after terminal cleaning in 260 intensive care unit rooms. Only 49.5% (1748) of surfaces were cleaned at baseline (95% confidence interval, 42% to 57%). Thoroughness of cleaning at baseline did not correlate with hospital size, patient volume, case mix index, geographic location, or teaching status. After intervention and multiple cycles of objective performance feedback to environmental services staff, thoroughness of cleaning improved to 82% (95% confidence interval, 78% to 86%). Significant improvements in intensive care unit room cleaning can be achieved in most hospitals by using a structured approach that incorporates a simple, highly objective surface targeting method and repeated performance feedback to environmental services personnel. Given the documented environmental transmission of a wide range of multidrug-resistant pathogens, our findings identify a substantial opportunity to enhance patient safety by improving the thoroughness of intensive care unit environmental hygiene.

Fouling characterisation of a PVDF membrane

Several studies have shown the importance of a biofilm on the membrane surface and some have identified EPS as the components responsible for membrane fouling. This study, performed within the framework of the European AMEDEUS project, investigates the membrane deposit, its composition and origin, using two industrial modules provided by A3 Water Solutions, which operated at pilot-scale for one year with typical biological operating conditions (SRT = 28 days, MLSS = 10 g/l). One of the modules was subjected to an intensive cleaning, using hydrogen peroxide, before being removed. Membrane sample deposits were taken on each module: differences were found between the fouled and the cleaned membrane in particular with regards to the organic fraction of the deposit, suggesting some changes in the biofilm after cleaning. The composition of the membrane deposit was also compared to the sludge supernatant and the permeate characteristics. Results showed the retention of biopolymers by the filtration step and their presence in the membrane deposit. However, all the biopolymers retained by the membrane between two maintenance cleanings were not found in the membrane deposit. They could have been removed by physical cleanings, linked to some compounds or not detected. Biopolymers probably play a role in membrane fouling but chemical and physical phenomena prevented the understanding of the fouling mechanisms.

Membrane bioreactor for water reclamation in Singapore

The Public Utilities Board (PUB) of Singapore embarked on MBR technology evaluation program in 2002. The three systems, i.e. Zenon system, Mitsubishi system and Kubota system, were set up in early 2003 and evaluated. Other MBR systems like Memcor MBR, Toyoplus MBR, Singaport Cleanseas MBR, Huber MBR and Asahi MBR were tested later on or is under testing. These trials have generated valuable information on the design and operation of the MBR systems under tropical environment in pilot scales. PUB decided to extend the pilot scale operations by building a 23,000 m3/d demonstration plant at Ulu Pandan Water Reclamation Plant. This plant was commissioned in December 2006. The product of this plant is supplied to industries as Industrial Water. The plant produces industrial water which is superior to all the requirements. The power consumption is about 0.55 kwh/m3 and no intensive chemical cleaning has been done since the start-up of the plant for about 7 months.

Cleaning endodontic files in a washer disinfector

The aim of this study was to compare the cleanliness of endodontic files that had been cleaned in a washer disinfector according to the file holding mechanism within the machine. Selected canals of extracted teeth were filed with new, unused files. One set of files (size 15 to 40) was used for each canal. A total of 192 files were used for cleaning and shaping. The files were divided into three groups. The first group was a control group containing 30 files, which were not cleaned in the washer disinfector. The second and the third groups were the experimental groups with 81 files in each group. These files were cleaned in the washer disinfector using different holding mechanisms (file holder or cleaning basket) for each group. The files were examined for visible debris under a light microscope at x45 magnification. None of the 162 cleaned files were totally free of organic debris. Comparison of the debris scores in the two experimental groups showed that the files in the cleaning basket group were significantly cleaner than those in the file holder group. The files in both test groups were significantly cleaner than those in the control group. Endodontic files cannot be totally cleaned using a washer disinfector alone. The instrument holding mechanism within the machine has a significant effect on the cleanliness of the files after one intensive cleaning cycle.

Summary of: Cleaning endodontic files in a washer disinfector

Aims The aim of this study was to compare the cleanliness of endodontic files that had been cleaned in a washer disinfector according to the file holding mechanism within the machine. Methodology Selected canals of extracted teeth were filed with new, unused files. One set of files (size 15 to 40) was used for each canal. A total of 192 files were used for cleaning and shaping. The files were divided into three groups. The first group was a control group containing 30 files, which were not cleaned in the washer disinfector. The second and the third groups were the experimental groups with 81 files in each group. These files were cleaned in the washer disinfector using different holding mechanisms (file holder or cleaning basket) for each group. The files were examined for visible debris under a light microscope at x45 magnification. Results None of the 162 cleaned files were totally free of organic debris. Comparison of the debris scores in the two experimental groups showed that the files in the cleaning basket group were significantly cleaner than those in the file holder group. The files in both test groups were significantly cleaner than those in the control group. Conclusions Endodontic files cannot be totally cleaned using a washer disinfector alone. The instrument holding mechanism within the machine has a significant effect on the cleanliness of the files after one intensive cleaning cycle.

Evaluation of innovative operation concept for flat sheet MBR filtration system

One of the most limiting factors for the extension and acceptance of MBR filtration systems for municipal and industrial wastewater is the impact of membrane fouling on maintenance, operation and cleaning efforts. One field of action in the European Research Project "AMEDEUS" is the development and testing of MBR module concepts with innovative fouling-prevention technology from three European module manufacturers. This article deals with the performances of the flat-sheet modules by A3 Water Solutions GmbH in double-deck configuration evaluated over 10 months in Anjou Recherche under typical biological operation conditions for MBR systems (MLSS = 10 g/l; SRT = 25 days). By using a double-deck configuration, it is possible to operate with a net flux of 25.5 l/m2.h at 20 degrees C, a membrane air flow rate of 0.21 Nm3/h.m2 of membrane to achieve a stable permeability of around 500-600 l/m2.h.bar. Additionally, it was observed that it is possible to recover the membrane performance after biofouling during operation without intensive cleaning and to maintain stable permeability during peak flows. The evaluated concepts for equipping and operating MBR systems will be applied to several full-scale plants constructed by A3 Water Solutions GmbH.

Intensive care unit environmental cleaning: an evaluation in sixteen hospitals using a novel assessment tool

Despite isolation precautions and enhanced hand hygiene product use, the transmission of healthcare-associated pathogens remains a major problem. Recent studies have confirmed that microbial contamination of the environment in intensive care units (ICUs) can lead to colonisation and infection of patients. Although environmental disinfectants have been used to minimise the spread of microbial pathogens, suboptimal cleaning may limit the effectiveness of such activities. In order to evaluate the thoroughness of cleaning near-patient surfaces, a transparent, easily cleanable and environmentally stable solution was developed that fluoresces when exposed to UV light. The solution was used to mark a standardised group of frequently touched objects in ICU patient rooms following discharge cleaning. These sites were then evaluated after at least two patients had occupied the room and at least two terminal cleanings had been completed. Evaluation of 2320 objects in 197 patient areas disclosed that 57.1% of the standardised sites were cleaned following discharge of the room's occupant in the 16 ICUs studied. Although high rates of cleaning (>80%) were found for toilet seats, sinks and tray tables, consistently low rates of cleaning (<30%) were documented for several objects at high risk of becoming contaminated with nosocomial pathogens, including bedpan cleaners, toilet area handholds, doorknobs and light switches.

Efficacy of cleaning and disinfection on pig farms in Ireland

Little is known about the effectiveness of the cleaning and disinfection methods used on commercial pig farms either in Ireland or worldwide. A National Salmonella Control Programme was implemented in...

Caregiver Asthma-Related Quality of Life in an Environmental Intervention Study to Alleviate Childhood Asthma Symptoms

ISEE-341 Objective: Recent studies have documented asthma symptom improvements among urban children with indoor allergen-reducing environmental interventions. Less attention has been attributed, however, to auxiliary effects on caregivers and other family members. The Healthy Public Housing Initiative (HPHI), a collaboration of university, government, and community partners, explored whether indoor environmental interventions (intensive cleaning, integrated pest management) may alleviate symptoms among urban children, and which factors may influence benefits for children and caregivers. Material and Methods: Trained Community Health Advocates visited with families monthly, administered Juniper Asthma Quality of Life (QOL) questionnaires for child and caregiver, and collected reports of child's symptoms, unplanned ED/clinic visits, and medication use. Data on perceived stress, violence exposures, and social support were also collected monthly for caregivers. Monthly quality-of-life data were analyzed for 51 caregivers of 58 asthmatic children in 3 public housing developments over 13 months. Longitudinal analysis with random intercepts was used to explore caregiver QOL improvements over the course of study, and in multiple periods. Several pathways for benefits in caregiver QOL are being explored, including (1) improvements in child's QOL, (2) direct influence of environmental improvements, (3) improved social support, and (4) asthma management. Results: Longitudinal analyses indicate significant improvement in caregiver QOL over the course of study. As previously shown for child's symptoms and QOL, caregivers show significant improvements in QOL before environmental intervention, indicating potential benefits of case management and support. Further analyses will explore the roles of social support and participation effects in predicting these preintervention QOL benefits. Conclusions: Results suggest that benefits of environmental interventions may be due to social as well as environmental aspects of intervention. Further analyses will explore the role of social support, caregiver stress, and other factors to explain observed improvements in caregiver QOL.

Synthesis and characterization of sulphonated core-shell latices in the size range between 30 and 80 nm

The objective of the current work was the synthesis of sulphonated core-shell nanolatices and to investigate to which extend it is possible to control the final surface charge of such latices. For this purpose differently sized polystyrene seed latices with average diameters in the size range between 30 and 80 nm were synthesized by emulsion polymerization. To obtain the final latices, a sulphonated comonomer was incorporated in the outer surface shell of the particles by further reaction of the seed latices with styrene and sodium styrene sulphonate (NaSS). In a first test series the seed latex surface was modified with four different amounts of NaSS. In a second test series four different seed latices were reacted with the same amount of NaSS. In the last set of reactions the seed latices were reacted with different amounts of NaSS and in these reactions the ratio of added NaSS to the specific surface area of the seed latex was kept constant to obtain differently sized latices of the same surface charge density. The yield of sulphonic acid groups in the particle shell was found between 57 and 74% after an intensive cleaning step by ion exchange. The results show possibilities for a reproducible synthesis of small sulphonated latex particles with a desired surface charge density.

Influence of cleaning frequency and membrane history on fouling in an anaerobic membrane bioreactor

Membrane fouling was evaluated in a side stream anaerobic membrane bioreactor (AnMBR) operated for the treatment of swine manure. The AnMBR consisted of an external tubular polyethersulphone ultrafiltration membrane module (diameter = 12 mm) connected to a six-liter mixed bioreactor. The system was operated for 135 days without chemical membrane cleaning resulting in a membrane flux of 5–10 L/m 2 h. Membrane fouling was dominated by a loosely attached fouling layer, which could be removed by flushing the tubular membrane. Intensive chemical cleaning after the 135 days of continuous operation resulted in an irreversible resistance of 3×10 12 1/m, equivalent to 1.3 times the resistance of the new membrane. More frequent chemical membrane cleaning using HNO 3 could not prevent the development of irreversible fouling. Equilibrium calculations and scanning electron microscopy with energy dispersive spectroscopy demonstrated that inorganic precipitation contributed to fouling of the membrane surface and in the membrane pores.

Cloth Media Filtration and Membrane Microfiltration: Serial Operation

A combined system comprised of a cloth media filter and a membrane microfilter operated in series was used to treat secondary effluent. The study objective was to investigate the effect of premembrane filtration on the maximum sustainable membrane flux, transmembrane pressure, and effluent quality. The maximum sustainable time-averaged flux under predefined operating conditions (i.e., 15-minute process cycle, 24-hour chemical cleaning cycle, and 30-day intensive cleaning cycle) was 127 L/m(2)x h. Typical flux rates for secondary effluent ranged from 40 to 55 L/m(2) x h. Effluent water quality from the combined system was high and independent of membrane flux and influent quality. Average membrane effluent water quality values were 0.04 NTU for turbidity and 1.4 mg/L for 5-day biochemical oxygen demand. Neither total nor fecal coliforms were detected. Based on the results presented herein, prefiltration would provide an annualized cost savings of approximately 12% over microfiltration alone for a 3.8 x 10(3) m(3)/d treatment facility.

DIFFERENTIAL EFFICACY OF ENVIRONMENTAL INTERVENTIONS FOR ALLEVIATING SYMPTOMS AMONG ASTHMATIC CHILDREN IN URBAN PUBLIC HOUSING

ISEE-305 Introduction: Asthma disproportionately impacts children in lower-income urban communities where environmental, social, and economic exposures exacerbate this multifactorial disease. Aim: The Healthy Public Housing Initiative (HPHI), a collaboration of university, government, and community partners, explored whether indoor environmental interventions may alleviate asthma symptoms, and which factors may modify efficacy of interventions. Methods: Seventy-eight children, aged 4 through 17, were recruited from 3 public housing developments; 58 were retained for longitudinal follow-up of 8 to 20 months. Cockroach and dust mite antigen, mouse urinary protein, and pesticides were sampled before and after indoor environmental interventions (intensive cleaning, Integrated Pest Management, mattress replacement, and air cleaners) to estimate pollutant reductions. Health outcomes data, collected monthly by trained Community Health Advocates, included Juniper Asthma Quality of Life (QOL) questionnaires for child and caregiver, reports of symptoms, unplanned ED/clinic visits, and medication use. Allergy testing, and spirometry were performed before and after interventions. Data on social exposures associated with immune function (stress, violence, social support) were collected monthly. Longitudinal analysis with random intercepts was used to assess improvement. Spline models were used to differentiate improvements during pre-intervention, post-intervention (<4 months), and longer term follow-up periods (4–18 months post-intervention). Effect modification was explored by dichotomizing the cohort by demographic, medical, social, and environmental risk factors. Pre-post changes in lung function score and caretaker QOL will be assessed. Results: Longitudinal analyses indicate significant improvement in QOL scores over the course of study (p<.001). Significant improvement is shown in the pre-intervention phase, indicating potential benefits of case management and support. The most rapid improvement occurred in the first four months following intervention. Boys showed higher QOL at time of intervention (p=.039), but made less improvement overall (p=.008). Older children showed higher QOL scores (p=.008), no difference in improvement. Children not: allergic to cockroach antigen made marginally more improvement (p=.06), as did non-obese children (p=.05). Children of families reporting higher life stress showed significantly lower QOL scores (p=.004), and those with reporting higher fear of violence showed less improvement (p=.036). Children receiving interventions during spring (vs. fall) made more improvement (p=.08), as did children spending less time around smokers (p=.015). No effect modification was found by medical care indicators. Discussion: Results indicate that environmental interventions may significantly improve the health of asthmatic children in urban public housing. It is less clear whether benefits are largely atttributable to environmental or social aspects of intervention. We found interventions to be more effective for girls, and for children not allergic to cockroach antigen, not obese, with lower exposures to tobacco smoke, violence, and stress, and who received interventions during spring months. Results indicate a need for coordinated interventions in the physical, social, and medical environments to alleviate severe asthma among inner-city children.

Rapid control of vancomycin-resistant Enterrococcus outbreak in an adult hematology unit at a tertiary hospital in Singapore

BACKGROUND/OBJECTIVES: While vancomycin-resistant Enterrococcus (VRE) infection is endemic in U.S. hospitals, little information exists concerning the problem in Southeast Asia. The recent VRE outbreak in our hospital marked the first outbreak in Singapore and called for the need to evaluate antibiotic utilization and strict infection control measures to prevent local epidemics. METHOD: In April 2004, vancomycin-resistant Enterrococcus faecium was cultivated from blood culture samples of two patients from the hematology unit of an acute tertiary-care hospital. Surveillance cultures, including rectal swabs or stool specimens, were then performed for the 14 existing hematology patients in the unit to assess the extent of the outbreak. Four patients yielded epidemiologically identical strains of VRE compared to the two index cases. A case control study was then conducted to determine possible contributory factors and antibiotic usage was analyzed to determine any correlation with the outbreak. Infection control measures instituted then were patient isolation with emphasis on contact precautions, quarantine of patients suspected to have contact with the index patients, ward closure and intensive environmental cleaning. RESULTS: A total of two infected and four colonizer cases were identified with identical pulsed-field gel electrophoresis (PFGE) patterns. The case control study showed that these patients had longer length of stay and received longer courses of antibiotics. Using logistic regression test, the use of metronidazole (p = 0.027) as well as the combination of metronidazole and cephalosporin group (p = 0.027) were significantly associated with the presence of VRE in the patient. CONCLUSION: Our study suggests that strict infection control measures successfully prevented further nosocomial spread of VRE. Further study is needed to determine the effectiveness of specific antibiotic therapy and cost-effectiveness of routine screening of VRE in preventing future outbreaks.

Membrane bioreactors for water reclamation

Singapore has been using dual membrane technology (MF/UF RO) to produce high-grade water (NEWater) from secondary treated sewage. Membrane bioreactor (MBR) has very high potential and will lead to the further improvement of the productivity and quality of high-grade water. This study was focused on the technical feasibility of MBR system for water reclamation in Singapore, making a comparison between various membrane systems available and to get operational experience in terms of membrane cleaning and other issues. Three MBR plants were built at Bedok Water Reclamation Plant with a design flow of 300 m3/day each. They were commissioned in March 2003. Three different types of submerged membranes were tested. They are Membrane A, plate sheet membrane with pore size of 0.4 microm; Membrane B, hollow fibre membrane with pore size of 0.4 microm; and Membrane C, hollow fibre membrane with pore size of 0.035 microm. The permeate quality of all the three MBR Systems were found equivalent to or better than that of the conventional tertiary treatment by ultrafiltration. MBR permeate TOC was about 2 mg/l lower than UF permeate TOC. GC-MS, GC-ECD and HPLC scan results show that trace organic contaminants in MBR permeate and UF permeate were in the same range. MBR power consumption can be less than 1 kwh/m3. Gel layer or dynamic membrane generated on the submerged membrane surface played an important role for the lower MBR permeate TOC than the supernatant TOC in the membrane tank. Intensive chemical cleaning can temporarily remove this layer. During normal operation conditions, the formation of dynamic membrane may need one day to obtain the steady low TOC levels in MBR permeate.