History in the making

Plum Creek Water Purification Facility

SYSTEM OVERVIEW Castle Rock Water provides the Town with safe, reliable drinking water for our residents’ immediate needs with future demands in mind. You are standing in a state-of-the-art facility that is helping the Town provide you with renewable water resources for the very first time. The unique design of this facility incorporates processes to treat both groundwater and surface water, giving the Town flexibility in choosing and obtaining water sources. The initial phase of this facility has a capacity to purify up to 4 million gallons per day and can be expanded up to 12 MGD. Included in this first phase of construction, the Town will have 6 MGD pretreatment capability, 12 MGD disinfection and chemical feed systems capacity, and 4 MGD filtering capacity (with a redundant 2 MGD train). The facility can be easily expanded to 12 MGD by adding a duplicate set of processes in the space that has been reserved.

TOUR STOPS 1. Control room 2. Laboratory 3. Aeration/Rapid mix 4. Flocculation 5. Sedimentation 6. Greensand filtration 7. Membrane filtration 8. Disinfection/finished water pumping 9. Chemical storage/feed systems 10. Membrane cleaning systems

History in the making

Plum Creek Water Purification Facility

Control room The water purification process is completely automated and controlled through programmable logic controllers (PLCs). Operators monitor and adjust the process through computers and can see the various equipment represented graphically on the screen. With the click of a mouse, operators can start and stop equipment; change set points that control the process; and see instantaneous information such as flow rate through the process, chemical addition rate, chlorine concentration, fluid levels in tanks, pressures within the system and other information used to optimize operations. The control system is secured, and each operator has a unique login. The system can be accessed remotely for monitoring and control, and access is secured and protected through firewalls to prevent unauthorized tampering with the control system.

History in the making

Plum Creek Water Purification Facility

LABoRATORY The laboratory consists of three separate areas: 1) operations lab 2) water quality lab 3) bacteriological lab Each area serves a separate purpose. The operations lab is for collecting samples and performing process control analyses (chlorine, suspended solids, pH, temperature, etc.). The water quality lab is for conducting more in-depth analysis of water samples to ensure compliance with water quality standards. The bacteriological lab is for determining the presence of bacteria in water samples through microscopic analysis. All the laboratory space is used to ensure that the water is safe for our consumption.

History in the making

Plum Creek Water Purification Facility

AEREATION/rAPID mix Aeration is the first step in the treatment process. Raw water flows into the two aerators located outside of the building. The aerators transfer oxygen to the raw water, oxidizing iron, while releasing dissolved gasses such as hydrogen sulfide. Water distributes and flows down a matrix of PVC pipes while a draft of air flows upward, in the opposite direction of the water. Water from the aerators flows into the rapid mix basin, which includes a flat-bladed turbine mixer. The rapid mixing action disperses chemicals into the raw water for further treatment in later processes. This system has the capability to disperse coagulant, potassium permanganate, and sodium hypochlorite into the water.

History in the making

Plum Creek Water Purification Facility

Flocculation The flocculation basin provides low intensity mixing to allow the small particulate matter in the water to come together, or flocculate, and form larger particles that will settle. It’s like a low speed blender that keeps everything completely mixed with a gentle mixing action. Three stainless steel paddle wheel flocculators, each with an independent mixing mechanism, rotate to mix the particles. The flocculation process tapers from higher intensity to form particles in the first stage, to lower intensity in the final stage to prevent large particles from breaking up.

History in the making

Plum Creek Water Purification Facility

SEDimentation The sedimentation basin settles flocculated solids from the process water using gravity. Water enters the basin and proceeds upward through inclined places. Solids settle onto the plates, which transfer the solids to the bottom of the basin. Settled water passes over metal plates with “V” notches cut into them, which allow water to pass through in a controlled manner. The water then flows into a collection channel where it flows to special filters that remove iron. A cable-driven solids collection system travels along the bottom of the basin to transport solids to the sanitary sewer via a collection manhole outside of the building.

History in the making

Plum Creek Water Purification Facility

Greensand filtration The greensand filters remove oxidized iron and manganese from the settled water and oxidize the remaining dissolved iron and manganese. Greensand is a natural sand having a dark greenish color caused by the presence of glauconite, a greenish mineral used as a fertilizer and water softener. Greensand readily attracts dissolved iron and manganese. Potassium permanganate, a strong chemical oxidizer, is fed either immediately upstream of the filter or into the rapid mix basin to maintain the filter’s ability to remove iron ensuring it continues to attract iron and manganese and remove it from the water. As the filters run, particles distribute onto the media, slowly increasing the water level in the filters. Once the water reaches a certain level that filter cell is backwashed, and the backwash water flows to the backwash waste basin where it eventually is recycled back to the rapid mix basin for reprocessing.

History in the making

Plum Creek Water Purification Facility

MEMBRANE filtration The heart of the treatment process is membrane filtration. This is where water is filtered to remove biological contaminants associated with surface water, much like a filter you might use while backpacking and filtering water from a spring or stream. Membrane filters are absolute barriers to disease-causing organisms and particulates larger than 0.1 microns (one-ten thousandth of a millimeter, 0.0001 mm, or about 0.0000039 inches). The 4 MGD membrane filtration process removes dirt, bacteria (including E. coli), viruses, and parasites such as cryptosporidium and giardia by rejecting particles larger than the membrane pores.

History in the making

Plum Creek Water Purification Facility

Disinfection/Finished Water Pumping This is the final process used to ensure that our water remains free of microbes and any remaining bacteria. This process will also protect the water as it is delivered to our customers. High pressure pumps move water into the Town’s distribution system, while adding ammonia (creating chloramines) provides a more stable disinfectant for the distribution system.

History in the making

Plum Creek Water Purification Facility

Chemical Storage and Feed Systems The chemical feed facilities store and add ferric chloride, potassium permanganate, citric acid, caustic soda, sodium bisulfite, sodium hypochlorite, and ammonia. The liquid chemical feed facilities include bulk storage tanks, feed pumps, and appurtenances. The chemical feed capabilities of the plant accommodate a wide range of chemical dosages from a low flow of 1 million gallons per day (MGD) to the peak flow of 12 MGD.

History in the making

Plum Creek Water Purification Facility

Membrane Cleaning System At set time intervals, the membrane filters are backwashed by reversing the flow of process water through the membrane to remove particles collected on the fibers. On a weekly basis, a chemical process called enhanced flux maintenance cleans the membranes more thoroughly. On a monthly basis, a more rigorous clean-in-place process chemically cleans the membranes. Pumps recirculate chemical past the membranes to clean off foulants. Sodium hypochlorite/caustic soda solution removes organic fouling while citric acid solution removes inorganic fouling.