As with many Puerto Rican water treatment facilities, the plant at Cidra uses surface water for raw water supply. Puerto Rican surface water, by nature, experiences widely fluctuating turbidity levels related to rainfall and watershed conditions. At a designed flow rate of 7.5 MGD, a carefully designed and operated water treatment plant was necessary for the Cidra facility to consistently meet USEPA turbidity standards for drinking water.
As the water travels from the intake structure to Tonka Water’s Heli-Cone™ upflow solids contact clarifiers, the water is first aerated. The aeration step provides for oxidation of iron and other easily oxidized inorganic contaminants and for gas removal. By employing aeration as the first step in treatment, chemical requirements are decreased, saving money with regard to chemical purchasing, chemical storage, and handling. After aeration, a head tank is provided to eliminate entrained air in the cone influent. Polymers and other chemicals are added for flocculation, coagulation, and disinfection as the water leaves the head tank. In-line static mixing ensures proper and complete mixing of the added treatment agents.
As the water enters the bottom of the clarifier, the unique ‘cone’ geometry creates a helical path along which the water flows upward through a sludge blanket and then over a weir edge. From there, the water is gravity fed into Centralator™ filters. This gravity filter system consists of eight equal filter cells in two banks. Each cell has a dual media filter bed, equipped with Tonka Water’s Simul-Wash™ backwash system, which employs a specially designed underdrain and baffled trough.
Similar to other Tonka Water installations on the island, the Cidra installation consistently reduces influent turbidity spikes of up to 1000 NTU and beyond, and produces filtered potable water well within USEPA and Puerto Rican Health Department standards.