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Remediation Technologies Screening Matrix, Version 4.0  
Chapter 19 Chemical Reduction/Oxidation
Table of Contents


19-2 Hazard Analysis

Principal unique hazards associated with chemical reduction/oxidation include:

Physical Hazards Chemical Hazards Radiological Hazards Biological Hazards

a. Physical Hazards

(1) Description: Because of the reactive nature of the chemical reagents (e.g. sulfuric acid, ozone, hyperchlorites), the system design and

19-1 Typical Process Flow for Chemical Reduction/Oxidation Process

materials of construction must be compatible with the reagents. Incompatible reagents and materials may cause fire or system over-pressurization and explosion.

Control: Liquid transfer equipment (pumps, piping, pipe fittings, valves and instruments) in contact with process liquids or chemicals should be fabricated from materials that are chemically-resistant to the liquid streams. Hydraulic Institute standards HI 9.1-9.5 discuss appropriate materials for pumping various fluids. Typical chemical charts can be found through the National Association of Corrosion Engineers (NACE). Provide chemical handling procedures. Substitution of equipment during construction should only be authorized by the design engineer. CONTROL POINT: Design, Construction, Maintenance

(2) Description: Runaway reactions (such as when concentrated acids or bases are mixed without sufficient cooling or dilution), which generate excessive heat and pressure within the system, may cause fire or explosion.

Control: Controls to help prevent the occurrence of runaway reactions include monitoring the injection of reagents into the process and the process temperatures at critical points, and providing for automatic feed shutdowns at preset temperatures. CONTROL POINT: Design, Operations, Maintenance

(3) Description: Prior to startup of the treatment unit, the system may be flushed with cleaning fluids that may be incompatible with the chemical reagents (e.g. chlorine, hyperchlorites) used in the treatment process. The commingling of these materials cause heat and pressure buildup within the system, possibly resulting in an explosion.

Control: The compatibility of the flushing agents and the reagents should be determined prior to their introduction into the system. CONTROL POINT: Operations, Maintenance

(4) Description: Sludge from the chemical reduction/oxidation process may plug waste lines if the rate of precipitation exceeds the rate of sludge removal. Plugged lines may result in an explosion from system over-pressurization, or fire from the pump motor overheating.

Control: Equipment to help prevent lines from plugging, such as auger-equipped waste lines or flow controls, may be used to help prevent plugged lines. Hazard warning alarms should also be installed to alert operators of system over-pressurization. CONTROL POINT: Design, Operations, Maintenance

(5) Description: Tank mixing equipment may splash chemical reagents (e.g. acids or hydrogen peroxide) or may entangle workers who come in contact with propellers or shafts.

Control: Where oxidation and reduction tanks have rotating mixers, design features should be included to protect people from harmful splashing or entanglement with shafts or motors. Lock-out/tag-out procedures should be implemented when performing maintenance activities on the mixers. CONTROL POINT: Design, Operations, Maintenance

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

Control: Electrical systems installed in areas that could potentially become wet or damp may require ground-fault protection. 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. Electrical system design must follow National Electrical Code NFPA 70 and CEGS 16415 (Electrical Work, Interior). CONTROL POINT: Design, Construction, Operations, Maintenance

(7) Description: Emergency shower/eye wash equipment required per 19 CFR 1910.151 is not always provided with adequate floor drains, thereby creating potential electrical hazards or walking surface hazards during required testing/use.

Control: Showers/eye wash equipment should be equipped with accompanying functional drains to isolate and collect the shower/eye wash water from unprotected electrical equipment and walking surfaces that, when wet, create slipping hazards. CONTROL POINT: Design

b. Chemical Hazards

(1) Description: Hazardous waste treatment using chemical reduction and oxidation poses worker chemical exposure due to the use and storage of toxic and reactive chemical reagents such as ozone and hydrogen peroxide. The reagents may react under certain conditions to generate heat and pressure within their storage containers. Spills involving the mixing of incompatible reagents may generate toxic vapors (such as hydrogen or chlorine), or generate sufficient heat to ignite combustible materials.

Control: All tanks and piping systems should be appropriately labeled. Controls to help minimize chemical hazards include temperature and moisture control in storage areas, storage areas segregated by dikes, and available spill control equipment. To help prevent these hazards, the compatibility of the reagents should be determined prior to placement in storage and following their introduction into the system. Material Safety Data Sheets should be consulted to determine the specific chemical hazards associated with the reagent chemicals. CONTROL POINT: Design, Operations, Maintenance

(2) Description: Chemical reagents are listed in CEGS 11242, Chemical Feed Systems. Workers may be exposed to these chemical reagents and/or to byproducts of chemical reduction/oxidation via the inhalation/ingestion/dermal exposure routes. Materials may be toxic (such as carbon monoxide and chlorine) or explosive (as with hydrogen).

Control: Controls to prevent worker exposure to chemical reagents include pressure testing all piping connections. Material Safety Data Sheets should be consulted to determine the specific health hazards associated with the specific chemical reagents utilized in the process. Material Safety Data Sheets will describe the specific personal protective equipment (PPE) required when handling the reagents and appropriate neutralization measures required in the event of a spill or exposure. Controls to prevent worker exposure also include testing the atmosphere inside tanks prior to each entry and ventilation of the system to prevent the accumulation of hydrogen, chlorine, or other toxic and explosive gases. Design the system so that areas where byproducts, such as carbon monoxide, chlorine, and hydrogen, may be generated are equipped with local exhaust ventilation. If the generation of ozone, CO, Cl2, and/or hydrogen is significant and can not be properly exhausted, install carbon monoxide and/or hydrogen monitors equipped with visual and audible alarms to alert operators to the problem. CONTROL POINT: Design, Operations, Maintenance

(3) Description: Effluent water may contain significant concentrations of reagents which can cause dermal and ocular damage. In instances where too much chemical has been used, the residual chemical can cause reactions and high temperatures. The under use of chemicals can cause incomplete process reactions which may cause over-pressurization of the system and subsequent leaks.

Control: Oxidation and/or reduction mixing/retention tanks should have instrumentation designed to monitor and set off alarms when chemical dosages or operational temperatures exceed preset limits. Control logic should be included in facility design to shut down chemical transfer systems under upset conditions. CONTROL POINT: Design, Construction, Operations, Maintenance

(4) Description: Flushing of the system prior to startup may cause chemical reactions and increased pressure with the reagents during system operation.

Control: Reactive chemicals in the treatment process may be incompatible. The compatibility of the chemical reagents used in the system operation should be reviewed prior to addition/mixing of these reagents. Material Safety Data Sheets, in accordance with ANSI 2400.1, should be available to operators. CONTROL POINT: Design, Operations, Maintenance

(5) Description: Reactive chemicals used in the process may corrode pipes, gaskets and connectors, causing leaks and worker exposure. Workers may be exposed to reactive chemical reagents including hydrogen peroxide, hypochlorites and chlorine.

Control: Process equipment should be properly designed/constructed with compatible materials. Hydraulic Institute standards HI 9.1-9.5 (Pumps - General Guidelines) contains the appropriate information for selection of materials. Reagent chemicals should be automatically fed into the system via a closed piping system. If manual addition is required, workers should wear proper protective clothing for the reagents. CONTROL POINT: Design, Operations, Maintenance

(6) Description: Employees may be exposed, through dermal or inhalation routes, to the soils, sludge, dust, or oversize rejects, when contaminated materials are being screened.

Control: During soil screening, water could be used to minimize the amount of dust generated. If this type of engineering control proves ineffective, dust monitoring can be performed to determine when respiratory protection (air-purifying respirators equipped with HEPA(N100, R100, P100) filters) should be donned. Chemical-resistant coveralls and chemical-resistant gloves (e.g. nitrile) will prevent employees from coming in direct contact with the contaminated soils and from carrying any contamination home with them on their clothing. CONTROL POINT: Operations

c. Radiological Hazards



d. Biological Hazards




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