Treatment shaft for combined sewer overflow detention.

A deep, large-diameter underground shaft to provide detention storage for combined sewer overflow control may be advantageous in urban environments, where space limitations require solutions with a small footprint. An underflow baffle wall is provided at the center of the treatment shaft to prevent short-circuiting of the flow. An additional objective is to maintain low headlosses through the structure. A physical model study was conducted to determine the effect of the bottom elevation of the baffle wall on the headloss and breakthrough curve for dye injected to the inflow. It was found that there is a considerable range of elevations for which the structure behaves acceptably in providing adequate contact time for disinfectant while maintaining small headlosses.

Microbial fouling of a reverse osmosis municipal water treatment system.

Microbial fouling of a municipal water treatment system using reverse osmosis was investigated. From a combination of growth and molecular assays, it was discovered that the prefilter unit concentrated and facilitated microbial growth, and such growth led to microbial fouling of the reverse osmosis unit. Few cells were observed in the prefilter influent, but substantial microbial contamination was observed in the prefilter effluent, and this correlated with increasing headloss across the prefilter. The effluent caused microbial fouling of the leading elements of the reverse osmosis unit, as determined by reduced permeate flow, analysis of the elements, and assays of the membrane foulant. Both the introduction of microorganisms to the reverse osmosis unit from the prefilter unit and headloss across the prefilter could be effectively controlled through cleansing of the prefilter housing unit with sulfuric acid. Such treatments must be performed at appropriate intervals to prevent subsequent microbial growth in the prefilter unit.