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U <br /> Strangio and Associates <br /> CIVIL& ENVIRONMENTAL ENGINEERS <br /> 1789 COTTLE AVE. <br /> SAN JOSE. CA 95125 - <br /> (408) 978-9604 FAX (408) 448-5284 <br /> October 26 , 1993 <br /> Ms. Kerry Sullivan <br /> .� <br /> San Joaquin County 3 <br /> 3199 <br /> Community Development GQ MUry')r UCrcLL, 9 <br /> 1810 E. Hazelton <br /> Stockton, Ca. 95205 -LANNINGDIyISID),y y` <br /> Dear Ms. Sullivan: <br /> In response to your query relative to the type of process <br /> that will be used at the City of Lathrop wastewater treatment <br /> plant and how would it be any different then two plants that <br /> you have personal experience with that are odorous(frequently in <br /> one case, and less frequently in another case) . <br /> A comparison of the three plants' would show that each plant had a <br /> different arrangement of processes which were used to stabilize <br /> their waste streams. However the two smelly plants use both aerobic <br /> and anaerobic processes(sludge digesters) while Lathrops' uses only <br /> aerobic processes. This is significant because anaerobic processes <br /> produce odors which most people characterize as being "smelly and <br /> disgusting" . The sludge digesters are used because they can <br /> produce methane gas which is used on-site to save energy, and they <br /> "hydrolyze" ( ie liquidize) solid material. The control of that <br /> process is not easy, plus the liquid is produced is very smelly. <br /> When the liquid is returned to the main treatment system there is <br /> ample opportunity for the smell to escape to the atmosphere. <br /> Lathrop will avoid this problem by using the aerobic stabilization <br /> inherent in the activated sludge process that is being used at that <br /> site. <br /> If you have the time it .would be worthwhile for you to visit the <br /> City of Hughson plant in nearby Hughson. This plant has won "The <br /> treatment plant of the Year" award four times. The process is <br /> similar to Lathrops, however it is not quite as sophisticated as <br /> Lathrop, since Lathrops also has a nutrient control process. <br /> Hughson's plant was built because the previous plant had such bad <br /> odors that a "Cease and Desist Order" was imposed. There have been <br /> no troubles since the new plant came on line. <br /> Specifically why the other plants are odorous is the result of the <br /> processes which are used and certain other factors. The plant to <br /> the west of Lathrop utilizes a "trickling filter" to oxidize the <br /> waste water. This process can be characterized as the minimum, or <br /> low end treatment process which will satisfy the Federal criteria <br />