Recent findings that Cryptosporidium inactivation occurs at technically and economically feasible ultraviolet (UV) doses have generated a wellspring of interest in UV disinfection for drinking water. Many utilities are considering UV disinfection as a means to meet future regulatory requirements at their existing facilities. Most utilities evaluating UV disinfection will be retrofitting existing treatment plants. In this article, capital, operations and maintenance, and total annualized costs were estimated for retrofitting existing facilities with UV disinfection after the filters and before the clearwell. Cost estimates were developed for a UV dose of 40 mJ/cm2, which would ensure at least 2‐log inactivation of Cryptosporidium, based on current research, and for a range of flows and filtered water qualities. The cost estimates presented indicate that UV disinfection is a relatively inexpensive method to achieve a high level of Cryptosporidium inactivation. As expected, annualized costs increased as system size decreased, although the costs were lower than those of other technologies providing similar levels of Cryptosporidium removal/inactivation.
A 0.63-L/s sludge flow liquid ion exchange alum recovery plant was tested at the Tampa (Fla.) water filtration plant. Two equipment setups were tested: one providing a rapid mix of sludge and solvent and the other a slow mix. Both were able to recover more than 90 percent of the aluminum and to reduce the dry weight of the sludge as predicted by acidification.Operating costs for a full-scale system were estimated at about the same as the value of the recovered alum. The economic considerations for installation would be based on treatment costs for the original sludge compared to those for the alum-free residual.Following extensive laboratory development'~' of the liquid ion exchange alum recovery process (outlined in Figure l), a demonstration plant was built at Tampa, Fla. The project was sponsored by the American Water Works Association Research Foundation, and funding for the demonstration plant was received from the foundation, the city of Tampa, Michigan State University, and RTR, SA. The objective of the demonstration plant was to determine scale-up efficiencies, to provide long-term operating data, and to evaluate process economics. This paper presents the results obtained at this plant. Previous papers should be consulted for details on process development, chemistry, the background of liquid ion exchange, and the rationale behind alum recovery. It should be emphasized that two different equipment setups were tested in Tampa. The first used a mixer-settler for extraction; the second used a contactor.*The city of Tampa's Hillsborough River water treatment plant is a 247.ML/d (65-mgd) conventional coagulation plant that treats a highly colored raw water. At the time of this project, Tampa utilized alum coagulation with sodium silicate addition as a settling aid (polymer has now replaced the sodium silicate). The sludge from the sedimentation basins had about a 0.3 percent suspended solids concentration, which can be gravity thickened to a suspended solids concentration of from 1 percent to 1.5 percent. Between 60 percent and 90 percent of the suspended solids are acid dissolvable. (See reference 3 for details on the characteristics of this sludge.) The Tampa sludge was chosen for the demonstration plant for two reasons: The 20 t/d (22 tons/d) of alum used at the plant made coagulant recovery an attractive treatment method. Because of the large amount of organic matter present in the *RTL, Lngano. Switzerland. 326 RESEARCH AND TECHNOLOGY sludge, it was felt that treating this sludge would be a demanding test of the liquid ion exchange process.
In a followup to a 1991 survey on 68 air stripping and granular activated carbon (GAC) treatment facilities in the US, the Organic Contaminants Control Committee of the AWWA Water Quality Division contacted each facility to obtain operating experiences and operation and maintenance costs associated with the use of these technologies. The committee's findings are summarized in this two‐part article. Part 1, which appears here, presents the finds regarding GAC facilities; part 2, which will appear in the February issue of Opflow, will highlight the air‐stripping facility findings.
In 1991, the Organic Contaminants Control Committee of the American Water Works Association Water Quality Division completed a report on 68 air stripping and granular activated carbon (GAC) treatment facilities in the United States. In a followup, the committee contacted each facility to obtain operating experiences and operation and maintenance costs associated with the use of these technologies to remove volatile organic chemicals (VOCs) from drinking water. The committee's followup findings are summarized in this two‐part article. Part 1, which appeared in last month's Opflow, presented the findings regarding the GAC facility questions; Part 2, which follows, highlights the air‐stripping facility findings.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.