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e <br /> A consulting <br /> have taken months.and com- engineering firm <br /> pletely disrupted the tourist handles day-today <br /> operation of the <br /> traffic that is vital to the local vacuum system and <br /> economy. With the smaller ; treatment facility. <br /> diameter vacuum lines that <br /> do not require a constant <br /> downward slope, trenches <br /> can be much narrower and <br /> shallower,usually 1.2 to 1.8 m <br /> (4 to 6 ft)in depth,so instal- <br /> lation time is greatly reduced, <br /> and far less heavy equipment <br /> is required. <br /> Vacuum sewer technol- <br /> ogy relies on differential air <br /> pressure to move wastewa- <br /> ter through sewer system <br /> mains. The process begins `" - a <br /> when wastewater flows from <br /> each house by gravity to a <br /> vacuum structure,commonly called a valve pit,which is station,where it is then pumped to the treatment facility. <br /> located nearby. Typically, two homes can be connected The wastewater moves so rapidly through the line that <br /> to a single valve pit. Each valve pit is equipped with a buildups of grease or sludge are rare. <br /> vacuum interface valve that activates when wastewater in The Provincetown vacuum system includes a total of <br /> the lower sump reaches a predetermined level,typically 8.8 km(5.5 mf)of PVC pipe,ranging from 100 to 250 mm <br /> 38 L(10 gal).When the valve activates,wastewater enters (4 in. to 10 in.) in diameter.There are approximately,250 <br /> the collector line, followed by a volume of air.A central valve pits in the system. The vacuum station, which is <br /> station maintains vacuum pressure within the sewer located in an attractive building in the downtown area, <br /> main collection lines.The wastewater forms a slug that is has a 22.7-m3(6000-gal)tank and two wastewater pumps, <br /> driven by the air through the sewer mains to the central as well as four 18.6-kW (25-hp) vacuum pumps. There <br /> has not-been a single complaint about the station since it <br /> opened in 2003. <br /> Day-today operation of the vacuum system and treat- <br /> ment facility is handled by a consulting engineering firm. <br /> Valve Initial operator training was provided by the vacuum <br /> Pit Package system manufacturer. <br /> Checkerboard District <br /> One of the unique aspects of this project is the"checkValve Pit <br /> Flexible - <br /> erboard" sewer district, in which residents can opt in. <br /> connector Before installation began,a letter was circulated to prop- <br /> Vacuum owners explaining that a new sewer system was about <br /> Interface to be installed. Because many residents were in compli- <br /> Valve ance with Title 5,they were not required to connect to the <br /> i t _ new system,Participation was voluntary. <br /> Approximately 340 property owners responded that <br /> they wanted to be connected to the new system.However, <br /> p"' by the time construction was finished,more than 500 cus- <br /> i t tomers were on-line. It seems that everyone now wants <br /> to be connected,which is a tribute to a system with near <br /> flawless performance during the past 3 years. <br /> The treatment plant currently has a capacity of 1890 <br /> m3/d (500,000 gal/d) but easily can be expanded to treat <br /> 2840 m3/d(750,000 gal/d).Like all aspects of the new sewer <br /> system,expandability was built into the plan. <br /> ©2007 Water Environment&Technology All rights reserved MAY 2007 <br />