2002-081-RES ACCEPT PROPOSAL OF FREESE & NICHOLS FOR PROFESSIONAL ENGINEERING SERVICES FOR PRODUCTION STUDY OF WATER TREATMENT OF COP

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Backwashing practice involves the use of high velocity wash water which is introduced into the filter bed in the direction opposite to the normal filtering flow. The backwash expands the filter beds 20 to 50 percent of the bed's original volwne. The sole use of backwash has not proven to be a satisfactory system for dual media filters' which allow a deeper penetration of solids into the filter bed. The deeper solids penetration requires a more efficient backwash system. In order to enhance the backwash capabilities with dual media, the Brown County Water Improvement District #1 Treatment Plant has utilized both 'air and water backwash. TIlls i1lows for a lower backwash water rate and provides for greater adaptation of the filter media through the introduction of air. The air and water backwash system maintains the filter media in a cleaner condition. 7) Multiple disinfection zone. The plant has three principal disinfection zones for flexibility of operation and optimization of disinfection contact values throughout the plant. Disinfection is currently accomplished by adding pre-chlorine in the water line between the terminal storage reservoir and the rapid mix basin (Zone 1). The free chlorine is converted to chloromines in the rapid mix. basin by the addition of ammonia..and continues through filtration (Zone 2). Disinfection is coritpleted through the transfer pwnp station and clearwell storage which is baffled prior to being delivered to the District's first customer (Zone 3). By utilizing multiple disinfection zones, disinfection by-products can be better controlled along with maintaining the proper disinfection residuals and contact times throughout the system. 8) Baffled Clearwells. The District was one of the first plants in Texas to add baffling in its c1earwell storage to enhance and improve the disinfection contact time. The clearwell .. contains five baffles varying in length from 40 feet to 60 feet in a circular tank. The baffles are made of a vinyl curtain fabric material. The baffling arrangement provided increased the baffling ratio in the clearwell from 20% to approximately 80%. The District can reduce the required free chlorine addition by approximately 50% and the required chloramine addition by 20%. Water Treatment Desie:n SummarY Capacity 10.MGD Flocculation Two-stage, variable speed drive Sedimentation Rectangular basin, 2 hr. Detention time with tube settlers Filtration Variable declining rate filter control, dual media (Anthracite coal and sand) with air assisted backwash. Disinfection Pre-chlorination (Zone 1) ahead of plant, Chloromines (Zone 2) through plant and (Zone 3) in baffled clearwell B. CPE Initial Assessment It is becoming ever more difficult for water system operators to assess the planning needs for compliance with changing and evolving regulations in the water industries. Operators of systems find it difficult to dedicate the time and resources necessary to .stay current with . .