20-2 Hazard Analysis

Principal unique hazards associated with liquid-phase carbon adsorption include:

a. Physical Hazards

(1) Description: Entering the carbon bed tanks for activities such as inspection, repair, and maintenance may constitute a confined-space entry.

20-1 Liquid-Phase Carbon Adsorption

Hazards associated with entry into confined space include asphyxiation from the lack of oxygen, exposure to toxic wastes, inhalation of fine carbon particles and byproducts, and engulfment/entrapment by the carbon bed.

Control: A confined-space entry program, including testing of the atmosphere inside the tanks, should be implemented to assess and control the hazards associated with confined-space entry. Appropriate personal protective equipment (PPE) (such as air-purifying respirator with filter/cartridge) may be required. CONTROL POINT: Operations, Maintenance

(2) Description: Sludge from the waste may plug transfer lines or piping at slow flow velocities. Plugged waste lines may cause tanks to increase pressure, possibly causing a leak which exposes workers to waste material.

Control: Adequate flow controls and pipe velocities should be designed to help prevent lines from becoming plugged. Filters may be used to remove solids prior to flowing through the carbon bed. CONTROL POINT: Design, Operations, Maintenance

(3) Description: Spent carbon used to remove explosive contaminants and other types of organic chemicals from water is a potential explosion and fire hazard during regeneration and removal from the tank.

Control: Spent carbon used to remove potentially explosive contaminants (e.g. explosives, highly volatile organic chemicals) from water should not be regenerated, as the heat used to regenerate the carbon may ignite or explode the adsorbed material. CONTROL POINT: Design, Operations, Maintenance

(4) Description: Carbon holding tanks or drums may leak or spill over into the surrounding areas, resulting in worker exposure during operations or loading and unloading of carbon.

Control: Carbon holding tanks or drums should have adequate spill containment. Spill and/or leak detection instruments can be installed to monitor for leaks or spills and set off alarms when appropriate. CONTROL POINT: Design, Operations, Maintenance

(5) Description: Water transfer system equipment (pumps, piping, pipe fittings, valves and instruments) in contact with contaminated liquids can corrode or dissolve to a point of failure, and cause damage to the facilities or exposure of workers to waste chemicals.

Control: Water transfer system equipment (pumps, piping, pipe fittings, valves and instruments) in contact with contaminated liquids should be fabricated from materials that are chemically-resistant to the contaminants in the system. Hydraulic Institute standards HI 9.1-9.5 discuss appropriate materials for pumping various fluids. Typical chemical resistance charts can be found through the National Association of Corrosion Engineers (NACE). Where leaks may occur, containment drip pans or receivers should be included in the design. Spill and/or leak detection instruments can be installed to monitor for leaks or spills and set off alarms when appropriate. CONTROL POINT: Design, Construction, Maintenance

(6) Description: Carbon beds are normally operated under pressure. Over-pressurization may result in explosion or fire from overheating of the pump motor.

Control: Hydro test all systems in accordance with CEGS 11225 (Downflow Liquid Activated Carbon Adsorption Units) before the system is put into operation. Add warnings for contents under pressure. CONTROL POINT: Design, Construction

(7) Description: Under certain operating conditions, biological growth can occur inside carbon beds. This growth may foul or plug the carbon bed flow pores, which may cause an increase in back pressure on the system. The back pressure may cause worker exposure to chemicals due to system leaks.

Control: In some cases, biocides may be fed into the system on a periodic basis. Other procedures may involve back-washing with biocides or bleaches to minimize or remove the biological growth. Often, the carbon is replaced and regenerated or disposed of. CONTROL POINT: Maintenance

(8) Description: Electrical systems in wet or damp areas can cause electrical shock to operating personnel.

Control: Verify that the hazardous area classifications, as defined in NFPA 70-500-1 through 500-10, are indicated on the drawings. All controls, wiring, and equipment should be in conformance with the requirements of EM 385-1-1, Section 11.G; NFPA 70; and CEGS 16415: Electrical Work, Interior for the identified hazard areas. Equipment should be grounded and/or provided with ground fault interrupter circuit (GFIC) protection if required by EM 385-1-1, Section 11 or NFPA 70 requirements. CONTROL POINT: Design, Construction, Operations, Maintenance

(9) Description: Permanent or semi-permanent treatment buildings may present life safety hazards such as inadequate egress, fire suppression systems, and/or emergency lighting systems.

Control: Permanent and semi-permanent treatment system buildings should be constructed in accordance with ANSI 58.1: Minimum Design Loads for Buildings and other structures; the National Fire Code; the National Standard Plumbing Code; Life Safety Code; and the Uniform Building Code. Depending on where the project is located, the structures must also comply with either the Air Force Manuals on Air Force bases, the USACE Technical Manuals on Army installations, or Local Building Codes on Superfund, BRAC, or FUDS project sites. CONTROL POINT: Design, Operations

(10) Description: Fires may result when this treatment technology is used for treatment of some components in wastes. For example, hydrogen sulfide may cause carbon bed fires because of its high heat release upon adsorption, or peroxides may auto-ignite.

Control: Select an alternate technology during design if the known or anticipated contaminants pose an unmanageable threat of fire. CONTROL POINT: Design

b. Chemical Hazards

Description: Workers may be exposed to waste chemicals from system leaks when activated carbon corrodes tanks and piping systems made from carbon steel.

Control: Carbon steel should not be used to contain activated carbon. Stainless steel, thermoplastic, or other chemically-resistant tank materials should be used. Tank interiors may be painted, coated, or lined to prevent contact between activated carbon and carbon steel. CONTROL POINT: Design, Construction, Maintenance

c. Radiological Hazards

Description: In some geological settings, dissolved naturally occurring radioactive materials (NORM) or radioactive contaminants may be drawn up with the groundwater. Depending on the chemical form, the radioactive component may be trapped by the activated carbon and concentrated in the filter to a point where a radiation hazard may develop.

Control: Should elevated levels of NORM or radioactive contaminants be present in the groundwater, a qualified health physicist should be consulted for proper guidance. CONTROL POINT: Maintenance

d. Biological Hazards

Description: NONAPPLICABLE

Control: NONAPPLICABLE