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Case Study

Pulp-Paper Mill Industrial / Municipal Impact

Hydrogen Sulfide Reduction and Corrosion Control

Problem

A pulp-paper mill in U.S. South East Georgia is tied to the municipal wastewater treatment system for a small city. The plant had operated for several years with escalating complaints from the city due to unpleasant odors emissions. Residents near the plant complained about discoloration of window blinds and shades, headaches and sore eyes. A determination was made that high levels of hydrogen sulfide emitted by the plant, directly into the air via inadequate air scrubber systems, or by effluents released into the sewer system, was the major cause of the reported problems.

The city reported chronic problems of line blowouts and corrosion in the sewer system. The problems were caused by crown corrosion, traced to high concentration of hydrogen sulfide in the sewer system. Leaching hydrogen sulfide into the concrete was causing rapid deterioration of the city’s system. The source of the problem was traced back to the pulp-paper mill. Government officials pressured the mill to find a solution to the problems created by the plant.

Solution

An Organic Product was applied into the sewer system via metering pumps at strategic locations at the mill site as well as in the city. Initial application levels were determined by the hydrogen sulfide levels and the maximum daily effluent flow rate at the site. The metering stations were “up-line” from problem areas with unacceptable levels of hydrogen sulfide emissions.

The Organic Product was applied at an initial rate of 50 PPM to the daily flow rate and upon achieving reduced hydrogen sulfide concentrations, the rate of product was reduced daily until a “maintenance” application of 12 PPM was reached. Permanent metering stations were set up at the plant and in the city.

The product was also injected into the circulation water of the air scrubber system at the plant. The daily application was set at 25 PPM. Tests in the gas stream showed a reduction of hydrogen sulfide by ~75%.

Corrosion tests were conducted at selected sites in the sewer system over 3 years. The application of the Organic Product delivered large improvements in corrosion levels. By reducing the H₂S in the system, the product had virtually eliminated the crown corrosion from leaching hydrogen sulfide. Corrosion levels were reduced from an average of ~20% – 90% annually before treatment to ~3% annually.

Conclusion

The application of the Organic Product produced dramatic improvements in the air quality at plant, as well as in the city. Complaints from residents and the government ceased. The expensive repairs to city sewer system were reduced. The relationship between the plant and the city was corrected.