tecnn1ca1 teatures .fereed paper
SYDNEY DESALINATION PLANT: PRE-TREATMENT PILOT TESTING C L Port, SJ Roddy Introduction
The Pilot Testing Program
Table 1. Elements of the pilot testing
Sydney Water is constructing a desalination plant to supplement Sydney's water supplies during the prolonged drought conditions and to provide for population growth. The plant will be a two-pass reverse osmosis desalination plant with a capacity of 250ML/d, upscaleable to 50 0M L/d.
The aim of the pilot resting program was to determine the most efficient pre-treatment process to produce filtered seawater su itable to be fed to a reverse osmosis plan t. Many membrane manufacturers require the SDI 15 (Silt Density Index-15 mins) of the filtered seawater feed to be below 3.5. T he pilot p rogram was to develop a process to reliably produce filtered seawater with an SDI 15 of below 3.
program.
Sydney Water Corporation has conducted a pilot-testing program to determine the most appropriate process for the RO pretreatment. The Pilot Plant Testing Program was required to optimise a generic conservative design to the most appropriate and economic pre-treatment process for seawater off the Kurnell peninsula. The pre-treatment pilot testing p rogram was conducted over l O months, commencing in October 2006 and concluding in July 2007. This paper reports how concl usions from the pilot plant rest results directly impacted the design of the plant, leading to significant capital and operating cost savings. This paper won a Best Paper Award at the Young Water Professionals Conferen ce, Brisbane, February.
The testi ng program was divided into phases focusing on the major process parameters as shown in Table 1.
Testing Phase Process Parameters Tested Coagulation
• Coagulation pH; • Secondary coagula nt (polyDADMAC) type and dose Flocculation
Deciding on the most appropriate and economic pre-treatment process.
• Flocculant type (polyacrylamide) and dose; • Flocculation conditions (G value and detention time)
Filtration
• Filtration rate; • Filter media size, type and configuration;
Results and Discussion The program tested the parameters o f conventio nal granular media filtratio n (GM F) pre-treatment shown in Table 1. The conclusions from each phase of the pilot testing program form the basis of the optimum pre-treatment process, shown in Figure 2.
• Type of coagulant and dose;
• Two-stage filtration
Results have shown that these treatment co nditions provide an effective pretreatment process for the range of raw seawater qualities experienced (5D13 of 1 1 - 25). Typically, the fi lter ripening time is approximately 4 hours with a filter run rime in excess of 110 hours, depending on raw seawater quality. T he test results obtained from the program provide a good level of confidence that reasonable filter run
Temporary Pilot Plants Compound Cronulla STP effluent outtetto ;Potter Point
Drill launch site ,Caltex :Refinery
Intake Structure
Trenched
outlet pipeline
Pump
below ground
Figure 1. Seawater Intake to Pilot Plan t - Combination HDD Tunnel and trenched pipeline. 90 MARCH 2008
water
Journal of the Australian Water Association