Start-Up and Initial Operation Of Singapore's 800,000 M3/Day (211 MGD) Changi Water Reclamation Plant

The new Changi Water Reclamation Plant (CWRP) in Singapore is designed for ultimate expansion to 2,400,000 m3/day (634 mgd). Construction of the initial 800,000 m3/day (211 mgd) phase began in 2001 and will be completed in mid 2008. Designed as a compact, underground facility, the plant incorporates stacked rectangular primary and secondary clarifiers along with the anoxic step feed process. Solids processing consists of centrifuge thickening, anaerobic digestion, centrifuge dewatering, and thermal drying. A 225,000 m3/day (59 mgd) “NEWater Factory”, or Reclaimed Water Production Plant, will be constructed under a Design Build Own and Operate (DBOO) concession on top of the liquid process modules to produce high grade water for indirect potable and non-potable uses. Phased start-up of the facility began in February, 2007 and has continued through 2008. Initial performance through May, 2008 has generally met expectations, resulting in excellent performance when the plant is not hydraulically overloaded. Partial nitrification and denitrification as intended with the anoxic step feed process was also established, which provided stable treatment, avoided significant pH depression, and achieved SVI values which were generally in the 80 to 120 105 mL/g range. Sludge digestion has performed as intended. Dewatered sludge cake has not met design expectations. Nocardioform foaming of the liquid treatment process adversely impacted performance during late 2007 and 2008 and also resulted in anaerobic digester foaming. Successful start-up of the CWRP has set the stage for on-going plant optimization.