NIOSH Urges Indoor Environmental Quality Improvements at Water Treatment Facility

A recently published health hazard evaluation report (PDF) presents NIOSH’s recommendations for improving indoor environmental quality and controlling hazards at a wastewater treatment plant adjacent to a state prison. An employee representative from the facility had contacted the HHE Program with concerns about ventilation issues, as well as potential exposures to process chemicals, bacteria, other pathogens, and mold.

In the HHE report, NIOSH staffers described the ventilation system in Filter Building 22 as “deteriorated and unrepairable” and noted that a return vent in Sludge Building 21 was partially blocked by a light fixture. In the laboratory, a mini-split HVAC system had been recently installed, which could control temperature and humidity but not provide outdoor air to or exhaust indoor air from the room. Employees used space heaters to supplement the building’s HVAC system. NIOSH has recommended that the employees consult with a licensed professional mechanical engineer for assistance in aligning the facility ventilation system with ANSI/ASHRAE Standard 62.1-2022, Ventilation for Acceptable Indoor Air Quality, and Standard 55-2023, Thermal Environmental Conditions for Human Occupancy.

In addition to indoor environmental quality issues, NIOSH staff members observed that the grinder used to break up debris splashed untreated wastewater on the employee walkway. The floor beneath the bowl used to collect quality check samples was wet, indicating that partially treated wastewater had splashed there as well. Powdered lime, used to control the acidity of sludge, spilled onto an employee’s personal protective equipment and clothing when they added the chemical to a tank. The HHE report noted that powdered lime may irritate or burn the skin and cause respiratory symptoms or lung disease when inhaled. Opening a hatch to remove treated sludge created an entry to a confined space, which employees could accidentally fall into. Water pooled inside and outside Sludge Building 21 created other slip, trip, and fall hazards.

NIOSH has recommended that employees install barriers, modify the sample collection station, and stock bags for the trash can near the grinder to reduce their exposures to untreated sewage. Substituting powdered lime with a liquid solution may reduce employees’ chemical exposures. Their employer was encouraged to provide them with dedicated work clothes and information on voluntary N95 respirator use, as well as increased access and storage for other PPE. Measures to improve confined space and slip, trip, and fall hazards included reducing the size of the sludge hatch opening and installing barriers and gutters to prevent water from accumulating. Although not the focus of the evaluation, NIOSH also encouraged the employer to improve communication with employees and evaluate their noise exposures.

A PDF of the report may be downloaded from NIOSH’s HHE report library.