An engineering investigation and evaluation of vortex devices as bubble makers for use in the removal of suspended solids from wastewaters was conducted. Specific objectives included the development and test of bubble makers capable of generating bubbles having mean diameters of about 100 microns with vortex devices having minimum liquid passageways of 1/4 inch or greater. Bubbles having a mean diameter of 80 to 85 microns, with virtually no bubbles greater than 130 microns, were successfully produced. This mean size and size range are substantially the same as bubbles produced by pressurized water processes at similar operating pressures. Bubbles were produced both by aspirating atmospheric air directly into the vortex unit, and by aspirating atmospheric air at the suction side of the pump, dissolving it, and precipitating it or effervescing it at the vortex unit. Sufficient data now exist, however, to design vortex systems for direct functional tests in conventional air flotation systems.

The project explored what is required and what happens if some or all of the sewage collected from a municipality is treated by advanced waste treatment (AWT) and put back in the water distribution system. Quality requirements and results of water reuse were examined by using computer programs for the preliminary design and costing of wastewater renovation by the lime-clinoptilolite-carbon processes of advanced waste treatment; for activated sludge treatment; and for pipeline conveyance of water. San Antonio, Texas was used as a specific case, at the two extremes of discharge all and reuse none and discharge none and reuse all. Costs for the conventional system and that reusing wastewater are discussed.

Full-scale tests were conducted on two variable-slope test sewers (12- and 18- inch diameters). During the tests, solids were first allowed to build up in both test sewers by passing domestic sewage through the sewers for durations of 12 to 40 hours and then were removed by hydraulic flushing. Formulas were developed which gave satisfactory predictions of several cleansing efficiencies and wave depths for the flush waves and sewer sizes studied. A prototype flush station developed can be inserted in a manhole to provide the functions necessary to pick up sewage from the sewer, store it in a coated fabric tank, and release the stored sewage as a flush wave upon receipt of an external signal. An estimate of costs of periodically flushing combined sewer laterals are given.