Mary K. Stinson

Challenges of Combined Sewer Overflow Disinfection by Ultraviolet Light Irradiation

This article examines the performance and effectiveness of ultraviolet (UV) irradiation for disinfection of combined sewer overflow (CSO). Due to the negative impact of conventional water disinfectants on aquatic life, new agents (e.g., UV light) are being investigated for CSO. This low-quality water with high flow rates, volumes, and suspended solids content requires the use of high-rate techniques for its disinfection. Although many pilot-scale studies have investigated UV irradiation as an alternative technology, to date no full-scale CSO treatment facilities in the United States are using UV light. A survey of the major pilot-scale studies investigating UV light as a CSO disinfectant suggests that UV light irradiation, correctly applied, is an effective alternative to chlorination for CSO. The success of disinfecting with UV light seems to be strongly dependent on water quality. Thus, pretreatment of CSO prior to disinfection is a major prerequisite to ensure UV light effectiveness.

EPA SITE demonstration of the BioTrol soil washing process

A pilot-scale soil washing process, patented by BioTrol, Inc., was demonstrated on soil contaminated by wood treating waste, primarily pentachlorophenol (PCP) and creosote-derived polynuclear aromatic hydrocarbons (PAHs). Although soil washing was the main object of this demonstration, the treatment train that was evaluated included two other BioTrol technologies for treatment of waste streams from the soil washer. The three technologies were: The BioTrol Soil Washer (BSW)--a volume reduction process, which uses water to separate contaminated soil fractions from the bulk of the soil. The BioTrol Aqueous Treatment System (BATS)--a biological water treatment process. The Slurry Bioreactor (SBR)--a BioTrol biological slurry treatment process conducted in an EIMCO BIOLIFT reactor. The sandy soil at the site, consisting of less than 10 percent of fines, was well suited for treatment by soil washing. The soil washer was evaluated in two tests on soil samples containing 130 ppm and 680 ppm of PCP, respectively. The BSW successfully separated the feed soil (dry weight basis) into 83 percent of washed soil, 10 percent of woody residues, and 7 percent of fines. The washed soil retained about 10 percent of the feed soil contamination while 90 percent of the feed soil contamination was contained within the woody residues, fines, and process water. The soil washer achieved up to 89 percent removal of PCP and 88 percent of total PAHs, based on the difference between their levels in the as-is (wet) feed soil and the washed soil.(ABSTRACT TRUNCATED AT 250 WORDS)

Performance of Ozone as a Disinectant for Combined Sewer Overflow

Disinfection of combined sewer overflow (CSO) minimizes the number of disease- causing microorganisms (pathogens) released into receiving waters. Currently, the primary disinfecting agent used in the United States for wastewater treatment is chlorine (Cl2); however, Cl2 produces problems in aquatic ecosystems. As a result, alternative disinfectants are being investigated. This article presents the results of a state-of-the-art review of the effectiveness of ozone (O3) for CSO disinfection. Data on major studies investigating CSO ozonation as well as its advantages and disadvantages are presented. Ozone inactivates a wider range of microorganisms than Cl2. In addition, O3 has a relatively high disinfection kill power, releases limited byproducts, is nonreactive with ammonia, and has an excellent ability for removing undesirable odor and color. The effectiveness of ozonation was found to be strongly dependent upon the occluding effects of suspended solids and influent quality. The reaction of O3 with water impurities is a major limitation. In general, ozonation can be an effective, but expensive, technology for CSO disinfection.

EPA SITE Demonstration of the International Waste Technologies/Geo-Con In Situ Stabilization/Solidification Process

This paper presents an EPA evaluation of the first field demonstration of an in situ stabilization/solidification process for contaminated soil under the EPA Superfund Innovative Technology Evaluation (SITE) program. Demonstration of this process was a joint effort of two vendors: • International Waste Technologies (IWT) of Wichita, Kansas, who provided the treatment process, specifically the proprietary additive called HWT-20, and • Geo-Con, Inc., of Pittsburgh, Pennsylvania, who provided both engineering and hardware for the in situ soil treatment. The field demonstration took place in April, 1988 at a site in Hialeah, Florida, contaminated mainly with polychlorinated biphenyls (PCBs). EPA tested the soil before and after treatment and the EPA evaluation of this process is based on results from this testing. A year later, in April 1989, EPA tested again the treated soil and results of that testing were compared to those of the demonstration. Results of the EPA evaluation of the IWT process, the Geo-Con ...

EPA SITE demonstration of BioTrol aqueous treatment system

BioTrols pilot scale, fixed-film biological system was evaluated, under the EPAs SITE program, for its effectiveness at removing pentachlorophenol from groundwater. The demonstration was performed in the summer of 1989 at a wood preserving site in New Brighton, Minnesota. The system employs indigenous microorganisms amended with a specific pentachlorophenol-degrading bacterium. Groundwater from a well on the site was fed to the system at 1, 3, and 5 gpm with no pretreatment other than pH adjustment, nutrient addition, and temperature control. Each flowrate was maintained for about two weeks while samples were collected for extensive analyses. At 5 gpm, the system was capable of eliminating about 96 percent of the pentachlorophenol in the groundwater and producing effluent with pentachlorophenol concentrations of about 1 ppm. At the lower flows (1 and 3 gpm) removal was higher (about 99 percent) and effluent pentachlorophenol concentrations were well below 0.5 ppm. The system consistently produced a completely nontoxic effluent at all three flowrates. Review of other data provided by BioTrol indicates that the process is also effective on other hydrocarbons, including solvents and fuels. The system appears to be a compact and cost-effective treatment for contaminated wastewaters requiring minimal operating attention once acclimated.

High-Rate Disinfection Techniques for Combined Sewer Overflow

This paper presents an overview of high-rate disinfection technologies for combined sewer overflow (CSO). The presented high-rate disinfection technologies depend on: ultraviolet light irradiation (UV), ozone (O 3 ), chlorination/dechlorination (Cl 2 ), chlorine dioxide (ClO 2 ), peracetic acid (PAA or CH 3 COOOH), and high-voltage electron beam irradiation (E-Beam), respectively. Discussions of the technologies include: commercial availability and extent of use, state-of-development when not commercial, and where available, performance data and cost of either full-scale or pilot-scale installation. Also discussed is utility of increased mixing in concert with any disinfection technology. Disinfection of CSO is generally practiced to control the discharge of pathogens into receiving waters. Therefore, the disinfectant used at a facility for treatment of CSO should be adaptable to intermittent (dry and wet weather flow) use. Other considerations include effectiveness, oxidation rate, safety, and cost. Commonly used disinfection by chlorination forms toxic residual byproducts. Newer disinfectants such as UV, ClO 2 , O 3 , CH 3 COOOH, and E-Beam have a far lesser potential to generate toxic byproducts. Since CSO flowrates and volumes are significantly greater than dry weather flows, use of high-rate processes requiring less tankage and space is more cost-effective than use of conventional processes. High-rate disinfection can be accomplished by: (1) applying mixing energy, (2) increasing disinfectant concentration, (3) using faster acting oxidants, (4) using high-energy irradiation, or (5) using combinations of these. Use of increased mixing with any disinfection technology provides better dispersion of the disinfectant and forces disinfectant contact with a greater number of microorganisms per unit time. The increased rate of collisions decreases the required contact time, which enables a high-rate disinfection.

Optimized Real-Time Control of Combined Sewerage Systems: Two Case Studies

The paper presents results of two case studies of Real-Time Control (RTC) alternatives evaluations that were conducted on portions of sewerage systems near Paris, France and in Quebec City, Canada, respectively. The studies were performed at real-scale demonstration sites. RTC alternatives use dynamic mathematical modeling and simulations to develop a program for a specific sewerage system to guide operation of automatic regulators when wet-weather flow is approaching. Advanced RTC alternatives also use a radar-based rainfall measurement and forecasting tool. Thus, the function of RTC-based combined sewer management is to assure efficient operation of the system and to maximize storage capacity of the existing sewerage facilities to contain combined sewer overflow (CSO) and there is cost saving aspect of this function. The first case study was conducted on a site, located northeast of Paris, France, that was a portion of the Seine-Saint-Denis combined sewer network with independent capture from other parts of the network. This site, controlled by six regulators, includes a primary settling and storage facility of 200,000 m 3 capacity, which can be operated either to increase settling efficiency of the retention pond or to increase the sewer relief capacity to decrease flood risk. This case study compared two RTC alternatives: the presently used Supervisory Predictive Control, aided by a radar-based CALAMAR system, and, a simulated, Local Reactive Control, without CALAMAR. The Supervisory Predictive Control was shown to be superior.

EPA SITE Demonstration of the Terra Vac In Situ Vacuum Extraction Process in Groveland, Massachusetts

This paper presents an EPA evaluation of the patented Terra Vac, Inc.s in situ vacuum extraction process that was field-demonstrated on a trichloroethylene (TCE) contaminated soil in Groveland, Massachusetts, under the EPA Superfund Innovative Technology Evaluation (SITE) program. The Terra Vac process employs vacuum for removal and venting of volatile organic compounds (VOCs), from the subsurface soil without excavation. Results of the eight-week continuous operation of the Terra Vac process in the field are as follows: high VOC extraction rates, achieving in eight weeks a total extraction of 1,300 lb of VOCs; an indication that this technology can achieve site remediation to the desired levels of VOC concentration in the soil; an indication that the process is effective in removing VOCs from soils of low permeability, such as clays, if soil has sufficient air-filled porosity; a correlatable decline in the VOC recovery rate with time that can be used to estimate operating time needed for site remediation; very reliable operation of the system in all weather conditions (test was performed in the winter); and process is economical with estimated costs per ton of treated soil between

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