The Amiss Water Treatment Plant (WTP) has a capacity of 78 million gallons per day (MGD) and is served from a combination of Cross Lake and 12 Mile Bayou. A number of supply, treatment and distribution system evaluations were performed to develop a recommended water plan and associated capital improvements plan (CIP) for the Shreveport water system. Recent drought year demands exceeded the rated plant capacity.
Water supply evaluations verified that the water supply is adequate to meet both existing demands and build-out demands. Some improvements at the intake are required, including the phased replacement of three existing pumps with slightly higher capacity pumps, extension of the supply line from 12 Mile Bayou for water quality purposes, and minor yard piping.
A full process evaluation, filter and backwash evaluation of 24 filters, regulatory review, hydraulic review were completed. Additionally, evaluation of a new intake and plant on the Red River at a new location was evaluated. The city has historically planned to add a second plant with a capacity of 35 MGD at a cost of about $150 million. Based on our evaluations of the Amiss WTP, we determined that settled water ozone contact and filtration are limiting plant capacity and the capacity of others processes can be expanded in-place in a phased approach to meet the build-out capacity at a much lower cost. A distribution system evaluation will be conducted to determine required improvements to convey build-out capacity from the WTP as well as develop solutions for several water quality issues.
The ozone portion of the project started with bench scale ozone testing to determine raw and settled water ozone doses, total oxidizable carbon (TOC) reduction, 2-methylisoborneol (MIB) and geosmin reduction, bromate formation, and assimilable organic carbon (AOC) generation. Based on the testing, an ozone dose was set at an initial dose of 3500 ppd with a build-out of 4500 ppd. Concept designs are under development for a new ozone system to replace the aged system, which generates less than 1 percent ozone and only feeds the settled water contactors, The new system will feed both the raw and settled water contractors and requires filter improvements including replacement of beaded caps with slotted caps and media replacement to sand and granular activated carbon
(GAC) for operation in a biological mode to help control AOC levels.
Several low-cost concepts have been developed to improve the treatment process through: changing coagulant and polymers, their feed points, and mixing energies; and expanding sedimentation capacity to 110 MGD within the existing basins. Concepts and associated opinion of probable costs are being developed for all supply, treatment and distribution; they will be used to evaluate and select a recommended plan resulting in a report and a phased CIP.
