SORB 33®;)
The SORB 33® arsenic removal system employs a simple process that flows pressurized water through a fixed bed pressure vessel containing the ferric oxide (Bayoxide® E33 granular or Bayoxide® E33P pelletized) media. As the contaminated water passes through the media, arsenic is adsorbed and removed to a level below 10mg/L. Since the Bayoxide media was developed to have a high capacity for arsenic, it achieves long run times before the media becomes exhausted. Exhausted media can be removed and sent to a non-hazardous landfill for disposal, meeting U.S. TCLP test.
Adsorption is a continuous process conducted at a specific flow rate or velocity, normally about 7 gpm/ft³, downward through a fixed bed absorber. Empty bed contact time (EBCT), which dictates the amount of water resident within the bed required to effect complete arsenic adsorption, is another key process parameter. An attractive characteristic of adsorption technology is its simplicity and relatively low cost. For example, coagulation/filtration has higher initial capital costs and is labor intensive, with labor costs often not adequately accounted for in operating cost estimates. In addition, this technology is more complex than adsorption, a key concern for utilities without centralized treatment plants. The technology requires frequent backwashing (water losses) and constant calibration of significant automation required for chemical dosing, backwashing and sludge management. However, coagulation/filtration can prove to be an effective solution when treating for high levels of multiple contaminants.
The SORB 33 system design and operation does not require cleaning, regeneration or any other complex process step required for competitive technologies. In addition, the SORB 33 process is a cost-effective solution from installation to full operation.
Severn Trent Services can accommodate flow rate capacities of 20 GPM (4.5 m³/hr) to 1,200 GPM+ (273+ m³/hr) per system with their SORB 33 arsenic removal systems.
- Large Water Systems: SORB 33 EAS
- 80 GPM to 1,200 GPM+ (18 m³/hr – 273 m³/hr+) per system - Small Water Systems: SORB 33 APU
- 20 GPM to 300 GPM (4.5 m³/hr – 68 m³/hr) per system
Layne Christensen LayneOx
Arsenic is a carcinogenic groundwater contaminant that occurs naturally in concentrations ranging from 0.1 to 40 ppm. The USEPA has set the MCL for arsenic at 10 ppb (10µg/L). Arsenic can be readily removed to concentrations below 10 ppb utilizing a variety of proven Layne technologies. Layne's engineers can evaluate your water quality, recommend abatement strategies, conduct technology verification pilot studies and design and install turnkey treatment plants.
The LayneOx™ BAT process co–precipitates arsenic in the presence of iron. The LayneOx™ filter media can be backwashed to regain capacity for many years of repeated use. The high catalytic activity of the LayneOx™ media accelerates the conversion of iron and arsenite thereby enabling the removal of total arsenic at high surface loading rates (5–8 gpm/sq ft). The LayneOx™ filter backwash water may be discharged to a POTW or to a recovery system. The resulting benign ferric arsenate can be dewatered and disposed as a non–hazardous waste subject to passing TCLP and CALWET criteria.
Arsenic History in North America
1943: The U.S. Public Health Service (US PHS) set a 50 µg/L standard for interstate water carriers based on short-term exposure effects
1975: EPA set the National Interim Primary Drinking Water Regulation at 50 µg/L . This standard has caused much controversy and debate in the federal government for over 20 years.
1980: EPA announced the availability of Water Quality Criteria Documents to protect bodies of water from pollutants under the Clean Water Act (45 FR 79318).
1985: EPA proposed (50 FR 46936) an MCLG of 50 µg/L based on the National Academy of Sciences (NAS) conclusion that 50 µg/L balanced toxicity and possible essentiality.
1986: Amendments to the Safe Drinking Water Act (SDWA) converted the 1975 interim arsenic standard to a National Primary Drinking Water Regulation (NPDWR), subject to revision by 1989.
1989: Review of the arsenic risk assessment issues caused the Agency to miss the 1989 deadline for proposing a revised NPDWR, and a citizen suit was filed against EPA. A consent decree was entered by the court in June, 1990 and was amended several times thereafter.
1992: Due to the potential significance of two internal cancer studies published in 1992 (Smith et al., and Chen et al.), the Agency decided to evaluate and incorporate this new risk information into the revision of the arsenic regulation.
August 18, 1994: EPA's SAB reviewed occurrence, treatment technology, and analytical methods and issued a report in July 1995.
November 1995: The final rule was postponed until January 2000, due to a delay in the EPA studies.
August 6, 1996: Safe Drinking Water Act Amendments of 1996 signed by the President.
Arsenic amendments added in Section 1412(b)(12)(A)
- Develop a research plan to reduce the uncertainty in assessing health risks from low levels of arsenic by February 2, 1997.
- Conduct the research in consultation with the National Academy of Sciences, Federal agencies, and interested public and private entities.
- May enter into cooperative agreements for research.
- Issue proposed regulation by January 1, 2000.
- Issue final regulation by January 1, 2001.
- Congress authorized $2.5 million per year from 1997-2000 for the studies. In 1996 and 1997 Congress appropriated $1 million each year for arsenic research.
January 2000: The issue of the proposed rule was missed.
June 2000: A proposal for a new rule was issued, setting the date for the final rule at June 22, 2001.
January 22, 2001: In the final days of President Clinton’s administration, the EPA posted a final rule in the Federal Register, five months ahead of schedule, lowering the standard from 50 to 10 ppb. At this time, the EPA also established a health-based, non-enforceable Maximum Contaminant Level Goal (MCLG) for arsenic of zero. 10 ppb is the accepted standard adopted by both the World Health Organization (WHO) and the European Union (EU).
March 1995: The EPA, under the new leadership of the Bush administration, withdrew the rule, citing the need for additional research on cost and health effects. They postponed the effective date of the new rule until May 22, 2001.
May 2001: The EPA postponed the effective date again until February 22, 2002, citing a need for public reaction and additional research and commissioning studies on the benefits of a new standard, cost expectations and health effects. Although the EPA under the Bush administration initially refused to implement the final rule of 10 ppb, they publicly recognized the need to lower the standard somewhere to a level between 3 and 20 ppb.
August 2001: The National Drinking Water Advisory Council (NDWAC) completed its report of the analysis and recommendations of the Arsenic Cost Working Group and delivered the results to the EPA. The NDWAC said that the EPA produced a credible estimate of the cost of compliance, but that other treatment options, like Point-of-Use, might allow smaller water systems to comply more cost-effectively.
August 2001: The Science Advisory Board (SAB) delivered its final report on the benefits of a lowered standard to the EPA.
September 2001: The National Academy of Sciences (NAS) released the results of the health effects study. The group reported that cancer risks are much higher than previously acknowledged under the Clinton and Bush administrations.
October 5, 2001: The EPA announced the availability of and information on viewing the three reports – the health effects/science report prepared by the National Academy of Sciences, the costs report of the National Drinking Water Advisory Council and the benefits report of the EPA’s Science Advisory Board. To view, visit these sites:
NAS report on health effects:
http://www.nap.edu/books/0309076293/html
NDWAC report on costs:
http://www.epa.gov/safewater/ars/ndwac-arsenic-report.pdf
SAB report on benefits:
http://www.epa.gov/sab/ec01008.pdf
October 15, 2001: The EPA announced it was seeking public comment on the three reports until October 31, 2001
November 1, 2001: The EPA announced it would lower the arsenic standard from 50 ppb to 10 ppb. Public water systems will have until January 2006 to meet compliance with the new rule.
November 26, 2001: President George W. Bush signed the bill for the new arsenic standard of 10 ppb. Public water systems will have until 2006 to meet compliance with the new rule.