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Published: 1979

Total Pages: 31

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A water recycle-reuse system researched and developed by the Virginia Highway and Transportation Research Council for treating water closet flush water was constructed at an existing rest area. An existing 10,000 gpd (37,800 lpd) biological wastewater treatment system and rest area piping system were modified to accommodate water reuse. The recycle-reuse system consisted of biological treatment (extended aeration) followed by gravity sedimentation and granular filtration. It was designed for 95% water reuse with 5% makeup from sewered potable uses such as wash basins. The field system became operative on November 15, 1976, and on August 31, 1977, an evaluation study was concluded. Based on results of the evaluation phase the water recycle-reuse design became an accepted alternative for resolving water supply and water pollution problems at Virginia highway rest areas. From September 1, 1977, through August 31, 1978, an implementation follow-up study was made. During this period reuse of flush water varied between 92.0% and 96.7%. Potable uses that were sewered amounted to less than 5%, resulting in recycle in excess of 95% without the use of makeup water. Recycled flush water was stable and was acceptable to the rest area user at all observed recycle levels. Operation of the biological and physical treatment units followed conventional guidelines. The biological system functioned satisfactorily at a low pH of from 5.5 to 6.5 and low alkalinity. The low pH and alkalinity resulted in complete nitrification and high ammonia nitrogen and nitrite nitrogen concentrations. Although high equilibrium nitrogen concentrations occurred they were not detrimental to the process. Biological solids were filamentous but were satisfactorily separated from the flush water by gravity sedimentation. The system satisfactorily responded to seasonal variations in waste characteristics and water reuse imposed by the users as well as seasonal climatic variations. Operation and maintenance requirements at the rest area site did not significantly increase as a result of the recycle-reuse system. Results from this study confirmed the conclusions of the evaluation study phase. The recycle-reuse system proved to be an acceptable and economical means of resolving water supply and water pollution problems at rest areas.