Kansas City, MO Projects

Particle and Organism Removal Processes at the Kansas City, Missouri Water Treatment Plant

Evaluation of Particle and Organism Removal Processes

Kansas City’s recovery of dissolved magnesium from precipitated softening solids in the primary sedimentation basin is an unusual and highly economic means of recovering an effective coagulant from what would otherwise be a waste material disposed of in landfill. Kansas City’s practice of coagulant recycling avoids virgin chemical purchase, transportation, storage, additional feed equipment, and those modest hazards associated with the handling of inorganic chemical coagulants.

However, examination of Kansas City Water’s extensive laboratory database on total organic carbon (TOC) revealed a potential disadvantage in recovering magnesium by recycling lime softening sludge to the primary basin influent. With the redissolution of magnesium hydroxide, the TOC increased in the primary basin by an average of 0.5 mg C/l or 12%. Much of this increase may have resulted from the return of floc-entrained particulate organic matter to the primary basin.

As expected, TOC removals in the secondary basins were substantial, averaging almost 2 mg C/l or 44%. Further reductions in the final basins and on the filters were marginal.

Removal of Plankton, Actinomycetes and Bacterial Cells

While most water utilities do not conduct analyses for plankton, their enumeration should be an excellent indication of the efficiency of particle removal processes for the removal of cysts and particle-associated organisms. Kansas City data on plankton confirm the effectiveness of primary sedimentation in consistently removing the majority of the microorganisms found in their influent water. Annual average plankton counts were reduced by over three-quarters (76%) during primary treatment.
Similarly, actinomycetes, a filamentous, branching bacterium associated with earthy/musty tastes and odors, was found to be reduced by 64% during primary treatment.

For the two treatment trains studied, lime treatment, flocculation and secondary sedimentation had accomplished additional bacterial cell reductions of 96% and 97.8%.

Starting with Missouri River water, overall bacterial cell removals observed after secondary settling averaged 98.4%.

References

John Reddy
Kansas City Water Services
1 NW Briarcliffe Road
Kansas City, MO 64116
816-513-2171
john_reddy@kcmo.org

Relevance

• Evaluation of magnesium as a recycled coagulant with respect to return of DOC to influent
• Assessment of enhanced coagulation and PAC for removal of TOC and TTHMFP