Carolina Transformer Superfund Site

Background

Years ago, the Carolina Transformer Company (CTC) had an electrical rebuilding and repair operation on a five-acre site in Fayetteville, N.C. After 15 years of operation, the company closed in 1982 and the site was abandoned. During operation, CTC had a storage facility for transformers and other equipment containing transformer oil contaminated with PCBs. The oil was not properly managed, stored or disposed of, and as a result, PCBs made their way into the surrounding acreage and ground water.

Consequently, in 1989, the North Carolina Environmental Services Division inspected the abandoned CTC site. The soil and groundwater contamination was confirmed, and the land was designated an EPA Superfund site under the Comprehensive Environmental Response, Compensation and Liability Act (also known as CERCLA or Superfund).

After many years of cleanup assessment, contractor proposals and red tape, 301 Environmental Services (Fayetteville, N.C.) was awarded a contract in January 2002 to treat and remove trace PCBs from over 1,500,000 gallons of contaminated water at this site (Figure 2). The level of PCBs in the water had to be reduced below 0.5 parts per billion (ppb) to conform with the discharge allowances of the state of North Carolina to the nearby Cape Fear River.

The Problem

A very low PCB discharge level (0.5 ppb) was required. In addition, transformer oil and PCBs at very dilute concentrations are extremely difficult to remove from water. This is especially complicated when mud, silt and clay are in the mix, which can all act as micro-absorbents and carry PCBs. Standard flocculation and filtration attempts could only achieved 70 ppb to 100 ppb PCB levels. The other problem with these suspended solids is that because of their type and size, they clog and blind-off filter media very quickly. Large backpressures develop rapidly, and tiny clay and silt particles carrying PCBs break up and bypass standard filters that don't capture sub-micron (<1 micron) particles.

In short, purifying water with trace oil, PCBs and sub-micron particulates such as silt and clay, is a very difficult and time-consuming endeavor. Typically impacted water of this type must be transported and treated off-site ( ex-situ). As an added treatment barrier, meeting discharge limits of 0.5 ppb on-site has, historically, not been economically feasible.

To meet this challenge, 301 Environmental asked MYCELX Technologies Corporation (Gainesville, Ga.) to design a complete pump and treat separation system to remove the PCBs and purify the water in-situ for discharge to the Cape Fear River.

The Solution

MYCELX Technologies, the manufacturer of MYCELX HRM™ (Hydrocarbon Removal Matrix) cartridge technology that is designed to bond and separate select hydrocarbons from water, in conjunction with the developers of a natural coagulant gel (provided by Engineering Sales Associates of Charlotte, N.C.), were able to develop an effective and inexpensive in-situ system capable of processing water at 180 gallons per minute (gpm).

The Results

To date, over 1,500,000 gallons of water have been purified to below detectable limits (BDL) of PCBs (<0.5 ppb) and discharged to the Cape Fear River easily complying with all aspects of the project's design parameters.

To produce this success, a combination of four technologies were used:

• Flocculation with select polymer additives (20,000 gallon batches).
  
• Particle Filtration -- a series of vessels and high efficiency filter media were used to remove particles to less than 1 micron.
  
• During the evolution of this project, a filter-aid product was added to improve the particulate filtration and associated pressure drops. The product is a natural coagulant gel called Chitosan. As this gel slowly dissolves, it attracts sub-micron particles, which agglomerate into larger, stable, easier-to-filter particles. This technology was very important to the over-all success of the project due to the type and size of suspended solids (i.e. sub-micron silt, mud and clay). The gel was implemented after gross particle removal at 50 microns and before fine particle removal.
  
• HRM™ Cartridges have an extremely strong bonding attraction for select hydrocarbon compounds. Examples of hydrocarbons that are effectively separated from water at up to 99.9 percent include oil, grease, gasoline, fuel, kerosene, hexane, benzene, toluene, chlorinated solvents and PCBs. In this application, the HRM™ Cartridges removed the PCBs to below detectable limits (BDL).

It is important to note that HRM™ Cartridges actively bond to hydrocarbons without desorption and operate at less than one pound per square inch (psi) pressure drop up to their saturation point.