Holnam's Artesia, Miss. Plant began operation in 1973 and was the last wet process cement operation constructed in the United States. The plant utilizes hazardous waste-derived fuel along with tire chips to supplement its traditional coal fuel.

The original quarry was located in an area directly east of the plant and operated for about 10 years before the new section of the quarry was opened up. Since operation, all stormwater from the plant was collected and channeled through a series of ditches into one outfall that ran off site. The water was continuously discharged, and the only treatment was to allow sulfuric acid to flow along with the water and reduce the pH.

The pH was monitored on a routine basis as the stream left the site, and the acid flow was adjusted according to the pH level of the stream. This was practiced until 1991, when the old section of the quarry was damned up and all stormwater was directed into it. The acid treatment system was shut down and the water began accumulating in the old quarry and eventually grew into a pond.

The water in the pond has been utilized back in the cement manufacturing process to the greatest extent possible. However, with an annual area rainfall of 57 in., it has not been possible to keep the pond level from continually rising. Due to the alkaline nature of the cement manufacturing process, the pH of the water is too high for the plant to discharge off site without treatment.

Last fall, a discharge pond was constructed to allow Holnam to move water from the quarry pond into the discharge pond, where the water could be sampled and tested upon release. Holnam can release 7.5 million gal. per day through the newly constructed pond. The original plans were to utilize the high-pH water in the quarry pond through a sprinkler system that kept an on-site sod farm watered. Eventually, it was realized that this would not use up enough of the quarry water to bring the level back down to a safe volume. The plant then decided to install a treatment system.

Holnam first considered using sulfuric acid again, but quickly realized that this was not the best alternative due to health and safety issues, as well as cost. It was decided to go with carbon dioxide (CO subscript 2) because it was safe and economical. Plant workers placed a 5,000-gal. water tank beside a drop box that allows water to flow into the new discharge pond. A 50,000-lb CO subscript 2 tank also was installed along with a vaporizer adjacent to the water tank.

The concept of the treatment is to pump the high-pH water into the tank, while bubbling the CO subscript 2 into the tank through a sparger on the bottom of the tank. The CO subscript 2 mixes with the water to form low concentrations of carbonic acid and brings the pH of the water down to reasonable levels (between 7 and 9).

The pH is monitored manually on a regular basis to ensure the right amount of CO subscript 2 is being mixed with the water. The plant has successfully discharged close to 100 million gal. to date, and the quarry pond is at a safe level. Holnam plans to continue the discharges until the majority of the water in the old quarry has been treated and released.