EBEAM as a Potential Wastewater Treatment Application – the Boston Electron Beam – part 2 of 4

 

There are over 30,000 accelerators operating worldwide with sales of $3.5 billion/yr and impact of over $500 billion/yr (Henning and Shank 2010). These accelerators are predominantly warm/copper technology. Because there is a need to treat high volumes in the environmental applications, superconducting accelerators are needed. Design commonalities for such accelerators, include an electron generating thermionic gun that creates a high-current electron beam, a cryostat with a Nb3Sn SRF cavity for acceleration, cryocoolers to reduce power demand and a coaxial input power couples for the RF cavity (Thangaraj and Ciovanti 5/10/2018 presentation at Fermilab).

The first foray into municipal water treatment using an electron beam has its origins in a study conducted by Sandia Labs and New Mexico State University that looked at the feasibility of sludge disinfection with electron beams and cesium 137 in 1974. The positive disinfection data obtained (Trump (not that one), 1980) led to the establishment of a large scale pilot facility at the Deer Island Treatment Plant in Boston, Massachusetts that focused on treatment of different sludges from the process at Deer Island (Kurucz, et al, 1995).  That study was funded by the National Science Foundation to investigate high energy electron disinfection of wastewater residuals (Bryan, 1990). The research team was led by MIT.

At the time, the Deer Island facility was operated by the Metropolitan District Commission, and subsequently the Massachusetts Water Resources Authority (MWRA – MWRA, nd).  The Deer Island facility started operations in 1968. At the time of the ebeam test, the plat had a capacity of 343 MGD, but experienced peaks of 850 mgd (MWRA 2020; ND).  Combined sewer overflows plagued the system (60 days per year).  Sludge disinfection was an emerging issue under the Clean Water Act rules.

The electron beam experiment was conducted at 70 gpm or 100,000 gpd, using a 50 kW/850 kvolt electron accelerator supplied by High Voltage Engineering Corp.  The e-beam first started operations in April 1976.  The liquid sludge was presented as a wide thin layer of liquid cascading downward through the electron beam.  All sludge must receive disinfection and therefore the setup requires that all of the sludge be penetrated by the electron beam. A 400 kilorad dosage was used for liquid sludge.  Trump et al (1979) found that the concentrations of salmonella, total coliforms, sand shigella were reduced between 4 and 5 orders of magnitude.  The most resistant parasite was ascaris.

The electron beam had benefits beyond pathogen reduction. Trump et al (1979) reported that trace polychlorinated biphenyls were effectively destroyed by as little as 10 krads in pure water.  Fragments disappeared at 50-100 kilorads.  The studies confirmed that the electron beam was capable of disinfecting raw, digested, waste activated primary and secondary and composted sludge effectively. (Trump et al 1979).