Ensuring safe reuse of residential wastewater: reduction of microbes and genes using peat biofilter and batch chlorination in an on-site treatment system.

AIMS: A batch chlorination system was optimized for on-site wastewater treatment and reuse system (OWRS) and its efficiency was evaluated for reducing viruses, protozoa, bacteria and antimicrobial resistance in cold and warm seasons. METHODS AND RESULTS: The OWRS performance in reducing microbial contaminants was determined by assessing three different faecal indicators (Escherichia coli, F-specific coliphages and Clostridium perfringens for measuring the disinfection efficiency of bacteria, viruses and spore-formers and surrogate for protozoa, respectively) using culture-based methods. Quantitative PCR was used to quantify pathogenic bacteria (Shiga-toxin-producing E. coli (STEC), Campylobacter spp., and Arcobacter spp.), a human-associated faecal marker (gyrB), and tetracycline resistant bacteria (tetQ). The levels of E. coli, coliphages and Cl. perfringens showed 5·4, 2·3, 2·5 log reduction, respectively, upon disinfection. In the final effluents, coliphages (1·7 × 102 PFU 100 ml-1 ) and Cl. perfringens (3·4 CFU 100 ml-1 ) were detected in 80 and 100% of the samples, but E. coli was not found. The removal and inactivation of E. coli and Cl. perfringens were not significantly different across the seasons, however, efficacy of removal and inactivation of F-specific coliphage was significantly reduced during the winter/spring season compared to the summer/autumn season (P = 0·009). The reduction of Arcobacter, gyrB and tetQ by 3·1, 2·3 and 2·3 log, respectively, was mostly due to peat biofiltration under the study conditions. CONCLUSIONS: This study demonstrated that peat biofiltration was the most important step of the OWRS to remove microbes and genes from wastewater before spray irrigation of the effluents. The irrigation system is not suitable for edible crops because of the potential presence of residual pathogens. SIGNIFICANCE AND IMPACT OF THE STUDY: On-site wastewater treatment systems are a practical option for reusing the wastewater for landscape, especially for those areas where geological and seasonal limitations impact the removal of microbial contaminants by soil infiltration.

Levels of polychlorinated biphenyls (PCBs) in fish: the influence on local decision making about fish consumption.

In 1989, the level of Aroclor 1254 (a mixture of polychlorinated biphenyls with 42 percent chlorine by weight) in fish collected from a recreational pond in Toledo, Ohio, was reported to be 44.4 milligrams per kilogram (mg/kg), prompting local health officials to declare a "no fishing advisory" for the pond. A second study conducted in 1990 did not identify elevated levels of polychlorinated biphenyls (PCBs) in fish tissue. In other words, the two studies gave conflicting results. The purpose of this study was to determine the level of Aroclor in fish tissues and then evaluate whether consumption of fish from the pond would pose a serious health risk. Fish samples collected on several occasions in 1998 and 1999 were filleted, and tissues were analyzed, as composite or individual samples, with gas chromatography. The levels of Aroclor 1254 ranged from 0.2 mg/kg in white crappies to 1.0 mg/kg in carp. These levels, while far less than the level reported in 1989, nevertheless were greater than 0.05 mg/kg, which is the maximum level established by the Great Lakes Fish Advisory Task Force for "no restriction in fish consumption." Levels of other Aroclor formulations ranged from less than the 0.02 mg/kg (the minimum detectable limit) to 0.1 mg/kg. Given current knowledge about the potential health consequence of exposure to PCBs and the results of this study, the authors have recommended that local health officials develop a new fish consumption guideline for PCBs. Any decisions about maintaining or lifting the restrictions on the pond, however, should be based on additional studies that determine the levels of other chemicals that are present in the pond and deemed hazardous to human health.

Evaluation of safety orientation and training programs for reducing injuries in the plumbing and pipefitting industry.

Construction workers are at increased risk for fatal and non-fatal injuries. This study examined the effectiveness of employee orientation and training in reducing injuries among plumbers and pipefitters. We searched the Occupational Safety and Health Administration's "recordable" injury data and "documentable" safety and training records for six plumbing and pipefitting employers in northwestern Ohio. During the period 1996 to 1998, 133 injuries were recorded with the duration of 2,541,432 working hours. The most common types of injuries were cuts, lacerations, and abrasions. The majority of injuries resulted from workers being struck by objects. The injury rate was significantly higher for small companies and longer working hours. No difference was found between traveling and local workers. Seventy-five percent of workers received safety orientations on injury prevention. Among workers who received safety orientations, only 3.4% experienced injuries, compared with 11.1% of workers without orientations. Safety orientations were associated with a significant reduction in injuries (odds ratio, 0.23; 95% confidence interval, 0.15 to 0.35). Proper safety orientation and training could reduce the risks for occupational injuries in construction workers.

Assessment of complete blood count variations among workers exposed to low levels of benzene.

The effect of benzene on white blood cell and red blood cell counts, hemoglobin level, mean corpuscular volume (MCV), and platelet count was investigated among workers in a small petroleum company. The investigated cohort consisted of 105 workers exposed to low levels of benzene between 1967 and 1994. The average level of benzene exposure per year ranged between 0.14 parts per million and 2.08 parts per million (8-hour time-weighted average). The mean complete blood count (CBC) demonstrated values within normal ranges. With the exception of white blood cells, all other CBC values were significantly reduced during the follow-up period. Length of employment was significantly related to the changes in MCV and platelet counts. The reductions in MCV were significant only among workers who had been employed for more than 10 years at this particular company. The findings of this study suggest that low levels of benzene may affect CBC values. CBC values may serve as a useful tool for biological monitoring for workers with low-level benzene exposure.

Injuries and illnesses among hospital workers in Ohio. A study of workers' compensation claims from 1993 to 1996.

Occupational illnesses and injuries are common problems facing workers and employers. The purpose of this study was to determine the nature and extent of illnesses and injuries among hospital workers in Ohio. All workers' compensation claims for 22 hospitals in Ohio during the period 1993-1996 were reviewed. The majority of the claims were for sprain and strain injuries. Most of the claims were approved. Back injury was the leading cause of injury in both genders, and females reported a significantly higher percentage of back injuries. The incidence rates for injuries and illnesses were lower than national rates for other industries. Generally, there was a downward trend in the number of claims during the study period. A negative linear trend in injury rates by hospital size was detected. Our findings suggest the need for safety programs, especially in smaller hospitals, with the goal of preventing sprain and strain injuries.

Prevalence of infectious diseases and associated symptoms in wastewater treatment workers.

Wastewater treatment workers (WWTW) are potentially exposed to a variety of infectious agents and toxic materials. We conducted a retrospective epidemiological study to examine the prevalence of infectious diseases and associated symptoms in WWTW. From a possible 242 WWTW, 150 completed a questionnaire that provided data pertaining to the diagnosis of an infectious disease or the prevalence of associated symptoms over a 12-month period. Comparison data were obtained from questionnaires completed by 54 college maintenance and oil refinery workers. The WWTW exhibited a significantly higher prevalence of gastroenteritis, gastrointestinal symptoms (specifically abdominal pain), and headaches. No significant differences were found with regard to respiratory and other symptoms. Employees classified by exposure categories did not exhibit significant differences in the prevalence of symptoms. While significant differences were found with regard to the health status of WWTW and controls, it appears that these risks are confined to symptoms and infectious diseases associated with the gastrointestinal system and are not inclusive of all such symptoms or diseases.

Comfort of personal protective equipment.

The degree of comfort of personal protective equipment (PPE) was investigated in an automobile encapsulating plant. Up to 96.2% of employees used one or a combination of PPE. Only 8% of the workers felt their respirators were comfortable, 30% tolerated their respirators, and 62% rated them as uncomfortable. The percentage of employees who rated their PPE (other than a respirator) as comfortable ranged from 32 to 52%. For comfort factor, coveralls/aprons rated 52%, safety glasses 51%, rubber gloves 42%, and hearing protectors 36%. PPE was tolerable (just acceptable) for about 30% of the employees. To increase the effectiveness and safety of PPE, the human-factor aspects of PPE design should be emphasized more and quality improvement should cover the wearability of PPE.

Medical and environmental surveillance.

Comparisons and contrasts are made between medical and environmental surveillance in New Jersey. These two approaches can be used together to address questions of association and prevention in occupational and environmental medicine, a field that needs to be expanded.

Formaldehyde exposure, acute pulmonary response, and exposure control options in a gross anatomy laboratory.

Formaldehyde exposure, acute pulmonary response, and exposure control options were evaluated in a group of 34 workers in a gross anatomy laboratory. Time-weighted average (TWA) exposure to formaldehyde ranged from 0.07-2.94 parts per million (ppm) during dissecting operations. More than 94% were exposed to formaldehyde in excess of the ceiling value of 0.3 ppm recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). The eight-hour TWA exposure of 31.7% of the subjects exceeded the action level of 0.5 ppm set by the Occupational Safety and Health Administration (OSHA). Reported symptoms included irritation of eye (88%), nose (74%), throat (29%), and airways (21%). Forced vital capacity (FVC) and forced expiratory volume in 3 seconds (FEV3) decreased, and FEV1/FVC increased during the exposure. The changes of FEV3 were statistically different from those of the controls. The results strongly support the necessity for designing and testing special local exhaust-ventilated worktables with necessary flexibility for dissecting operations.

Bioactivation of bis[p-nitrophenyl]phosphate by phosphoesterases of the earthworm, Lumbricus terrestris.

In view of the ability of several phosphoesterases to hydrolyze organophosphates to toxic phenols, the bioactivation of bis[p-nitrophenyl]phosphate (BNPP) by the earthworm Lumbricus terrestris was investigated. In a contact toxicity test, BNPP was was less toxic than the metabolite p-nitrophenol (PNP), but more toxic than the metabolite p-nitrophenylphosphate (PNPP). Results from an artificial soil test (soil containing BNPP) revealed that the phosphomonoesterase and phosphodiesterase activities from the enteric tissue of the annelid could be selectively depressed without significant reduction of these activities in other tissues. Since these esterase activities are 5 to 7 fold higher in the enteric tissue, these results suggest that the phosphoesterases in the annelid participate in the activation of BNPP to the more toxic metabolite, p-nitrophenol.

The role of enteric bacteria in the anaerobic metabolism of 5-aminosalicylate.

The primary (and inactive) enteric metabolite of 5-aminosalicylate is N-acetyl-5-aminosalicylate. Previous studies have demonstrated acetylation of this anti-inflammatory agent by intestinal and bacterial homogenates. To assess the contribution of anaerobic bacteria to the N-acetylation in vivo, we have measured the production of N-acetyl-5-aminosalicylate in anaerobic microculture. Our results indicate that enteric bacteria play a minor role in N-acetylation, but may contribute to the production of other metabolites of pharmacologic and toxicological interest.