Online evaluation of bacterial cells in sand filter effluents during full-scale treatment of drinking water

Ensuring the microbiological safety of drinking water is critical to protect public health. This study aimed to evaluate the reliability of real-time bacteriological counter coupled with an online dialysis membrane-based pre-treatment system for continuously monitoring bacterial cell counts in sand filter effluents of a full-scale drinking water treatment plant. The pre-treatment system, which included anion exchange resins (porous polymeric microbeads that trap ions for releasing other ions) for dialysate regeneration, successfully achieved the stable attenuation of background interfering substances (humic acids) during the 19-d test. The real-time bacteriological counter equipped with the pre-treatment system provided a continuous profile of bacterial cell counts in the sand filter effluent (0.2-2.5 × 10⁴ counts/mL). The online analysis identified different timing of concentration peaks between particle and bacterial cell counts after backwashing. Bacterial community analysis revealed that Proteobacteria, Planctomycetes, and Cyanobacteria were the dominating phyla. Further, total bacterial cell counts determined by fluorescence microscopy and SYBR® Green I staining, a commonly accepted parameter, was found to be an indicator of online-monitored bacterial cell counts. The results indicated the potential of monitoring the bacterial cell counts in a sand filter process for providing an early warning of filter failures, which can allow plant operators to diagnose the overall system and provide countermeasures.

Laparoscopic surgery produced less surgical smoke and contamination comparing with open surgery: the pilot study in fresh cadaveric experiment in COVID-19 pandemic

Background

The SARS-CoV2 virus has been identified in abdominal cavity of the COVID-19 patients. Therefore, the potential viral transmission from any surgical created smoke in these patients is of concern especially in laparoscopic surgery. This study aimed to compare the amount of surgical smoke and surgical field contamination between laparoscopic and open surgery in fresh cadavers.

Methods

Cholecystectomy in 12 cadavers was performed and they were divided into 4 groups: laparoscopic approach with or without smoke evacuator, and open approach with or without smoke evacuator. The increased particle counts in surgical smoke of each group were analyzed. In the model of appendectomy, surgical field contamination under ultraviolet light and visual contamination scale between laparoscopic and open approach were compared.

Results

Open cholecystectomy significantly produced a greater amount of overall particle sizes, particle sizes < 5 μm and particle sizes ≥ 5 μm than laparoscopic cholecystectomy (10,307 × 10³ vs 3738 × 10³, 10,226 × 10³ vs 3685 × 10³ and 81 × 10³ vs 53 × 10³ count/m³, respectively at p < 0.05). The use of smoke evacuator led to decrease in the amount of overall particle sizes of 58% and 32.4% in the open and laparoscopic chelecystectomy respectively. Median (interquatile range) visual contamination scale of surgical field in open appendectomy [3.50 (2.33, 4.67)] was significantly greater than laparoscopic appendectomy [1.50 (0.67, 2.33)] at p < 0.001.

Conclusions

Laparoscopic cholecystectomy yielded less smoke-related particles than open cholecystectomy. The use of smoke evacuator, abeit non-significantly, reduced the particles in both open and laparoscopic cholecystectomy. Laparoscopic appendectomy had a lower degree of surgical field contamination than the open approach.

Laminar airflow versus turbulent airflow in simulated total hip arthroplasty: measurements of colony-forming units, particles, and energy consumption

BACKGROUND

The optimal type of ventilation in operating theatres for joint arthroplasty has been debated for decades. Recently, the World Health Organization changed its recommendations based on articles that have since been criticized. The economic and environmental impact of ventilation is also currently an important research topic but has not been well investigated.

AIM

To compare how large, high-volume, laminar airflow (LAF) and turbulent airflow (TAF) ventilation systems perform during standardized simulated total hip arthroplasty (THA), as they pertain to colony-forming units (cfu), particle counts, and energy consumption.

METHODS

Two identical operating theatres were used to perform simulated THA. The only difference was that one was equipped with LAF and the other with TAF. Cfu and particles were collected from key points in the operating theatre, and energy was measured for each simulation. Thirty-two simulations were done in total.

FINDINGS

LAF had significantly reduced cfu and particle count when compared with TAF, at both 100% and 50% air influx. Furthermore, it was shown that lowering the air influx by 50% in LAF did not significantly affect cfu or particles, although reducing the fresh air influx from 100% to 50% significantly lowered the energy consumption. Most simulations in TAF did not meet the cleanroom requirements.

CONCLUSION

Cfu were significantly lower in LAF at both 100% and 50% air influx. It is possible to reduce fresh air influx in LAF operating theatres by 50%, significantly reducing energy consumption, while still maintaining cfu and particle counts below the ISO classification threshold required for THA surgery.

Surface and passive/active air mould sampling: A testing exercise in a North London housing estate

Despite indoor mould being one of the most common problems in residential properties in the UK, there are not any widely accepted methodologies for its measurement. This paper focusses on this problem of measurement and reports on the findings from a rigorous testing scheme carried out to quantify air and surface mould concentrations and particle counts within 71 rooms from 64 properties in North London, some with and some without visible mould. The aim was to investigate the potential of passive and active air sampling strategies (sampling from still and actively mixed air, respectively) to explain visible mould, and understand how home/room characteristics correlate with the obtained readings. Airborne mould levels were quantified using an Andersen sampler (passively and actively), as well as by a chemical method based on the quantification of the N-acetylhexosaminidase (NAHA) activity (actively), which was also used to quantify surface mould. The mould levels were then correlated against physical characteristics of the tested homes/rooms, collected by means of survey sheets developed as part of this study. The findings did not reveal any independent variable governing all or most of the response variables, but a complex analysis suggested that whether it is a house or a flat could depict mould levels in the air and on the surfaces. It was also shown that a robust testing protocol should combine air and surface based methods, and an active air sampling strategy leads to a more accurate appraisal of airborne mould levels. Finally, the results showed that while there is some correlation between visible mould (and other moisture induced problems such as condensation) and measured air mould concentrations, lack of visible mould within a room does not necessarily mean low air mould concentrations, and thus one should not rely solely on visual inspection.