Improving Flocculation Component of "Front-end" Treatment
Coagulation and flocculation are key steps in the front end of the water treatment process. Coagulants such as aluminum sulphate and polyaluminum
chloride are added to raw water in rapid mixers, where they chemically bind and clump suspended and colloidal material. The coagulated water is
distributed among six horizontal paddle-wheel flocculators, where it is slowly mixed as it flows over and under baffles to build "floc" particles. The
water is distributed via flumes to CWA's settling basins, where the floc settles out of the water.
In 2014, CWA began a project to improve the Treatment Plant's rapid-mix trains and flocculation basins. This work included replacement of flocculator
shafts, paddles, drives, motors, controls and electrical components in each of six flocculators.
It also includes the installation of electrically actuated valves at the effluent of each of six flocculators and the replacement of manual valve
operators with motorized operators on the two blend tank weir gates and six basin effluent gates. These improvements will enable immediate isolation of
a treatment train, flocculation basin, or settling basin, respectively, if a treatment upset occurs. This enables plant operators to correct the issue
while limiting the flow of water to the next step of treatment. Previously, isolation of these components involved a labor-intensive, time-consuming
manual process. During this project, improvements are also being made to the flumes, which distribute the water from the flocculators to the settling
basins. With the installation of valves and baffles, the flow pattern of the existing flumes will be modified to achieve better flow distribution from
the six flocculation basins to the four process settling basins. The new flocculator controls and status indicators are integrated with the Plant's
Supervisory Control and Data Acquisition (SCADA) system. Following significant progress in 2014, project completion is anticipated by September 2015.
Upgrades of Chlorination Equipment are Completed
Chlorination is a crucial process to meet regulatory requirements for proper disinfection of treated water. In 2014, CWA completed the timely
replacement of the Treatment Plant's chlorination equipment, which feeds gaseous chlorine in a gas/water solution at five points in the treatment
The project was undertaken in conjunction with CWA's chlorine risk management plan. A process hazard analysis compared the existing system with the
proposed new system to assure that the new system would provide equal or better process hazard control. The project improves reliability and treatment
process control as well as safety.
The project replaced seven chlorinators, three evaporators, and two vacuum feed regulators. It added a third vacuum feed regulator, renewed all
chlorine liquid and gas piping, replaced two existing chlorine container scales and added a third scale, and replaced leak detector alarms. The house
water supply was upgraded with a redundant feed to the chlorine injectors. Automated chlorine feed controls and status indicators were incorporated into
the Plant's SCADA system.
Improvements to the chlorine storage building included an additional door to improve egress, a new roof, a new bridge crane and hoist for handling
chlorine containers (which weigh 3,500 pounds), modifications to the internal structure of the building to better isolate electrical equipment and
electrical system improvements.
To assure safety during construction, the Authority shut down the gaseous chlorine feed system and removed all containers from the facility. During
construction, liquid hypochlorite (bleach solution) was used for disinfection. Tanks and feeds were housed in a temporary building equipped with
Project cost: $1.5 million
Hydroelectric Facility Improvements Protect Migratory Fish and Eels
CWA operates a 500-kilowatt hydroelectric facility at Pine Grove Dam when reservoir inflow conditions are sufficient, typically when the inflow exceeds
the total of the minimum downstream release and water supply requirements by 50 million gallons per day.
In 2014, CWA completed improvements to the hydroelectric facility at the Treatment Plant to protect migratory fish in the Octoraro Creek from becoming
trapped in the tailrace pool. These include installation of piping to ensure a continuous supplemental flow of water into the tailrace pool and
installation of a rock vane in the tailrace pool outlet, which concentrates the flow from the tailrace to the main channel of the creek and improves
fish movement from the pool to the creek. Water quality monitoring equipment was also installed in the tailrace pool to monitor pH, dissolved oxygen,
temperature, and water depth and incorporated into the Plant's SCADA system. In addition, CWA modified the runner hub of the turbine from a food-grade
oil-filled hub to an air-filled pressurized hub to prevent an oil release in the event of a seal leak and modified the discharge piping of the
powerhouse sumps to eliminate their direct discharge into the tailrace pool.
CWA also installed a seasonal eel ladder at the 1904 masonry dam located just above the Pine Grove covered bridge to facilitate the upstream migration
of eels up the main branch of the Octoraro Creek.
This work was done in consultation with the Pennsylvania Department of Environmental Protection, Federal Energy Regulatory Commission, Pennsylvania Fish
and Boat Commission, and National Fish and Wildlife Service as corrective action to reduce potential for fish mortality in the tailrace pool.
Total project cost: $1.2 million
2014 Water Main Rehabilitation serves Trainer and Chester
Supplemental project accelerates the program toward 2024 goal
CWA completed the annual 2014 Water Main Rehabilitation Project, focusing on the area of the older sections of the distribution system serving 395
customers in the Borough of Trainer and the City of Chester, Delaware County. In order to accelerate the program to complete the rehabilitation of the
distribution system by 2024, the Authority awarded a contract for a Supplemental Water Main Rehabilitation Project in Lower Chichester Township, Trainer
Borough, the City of Chester, and Aston Township, Delaware County. The work was completed in the first three municipalities, and it continues in Aston
Township during 2015.
In addition, CWA completed three projects to rehabilitate, renew, or reinforce sections of water main serving the City of Chester, Aston Township, and
The annual Water Main Rehabilitation Project involved the following components:
- Rehabilitation of 9,380 feet of 6,- 8-, and 12-inch diameter cast-iron mains in Trainer and Chester and 2,935 feet of 20-inch diameter cast-iron
mains in Chester using a cleaning and cement-lining process
- Renewal of 64 services and 7 fire hydrants
Total 2014 Water Main Rehabilitation cost: $3.3 million
The Supplemental Water Main Rehabilitation Project involves:
- Rehabilitation of 6,440 feet of 12-inch diameter cast-iron water main along Laughead Ave. and Township Line Rd. in Lower Chichester, Trainer,
and Chester (completed)
- Rehabilitation of approximately 3,000 feet of 12-inch diameter cast-iron water main along Concord Road in Aston (to be completed in 2015)
Total Supplemental Water Main Rehabilitation cost: $1.8 million
Since 1974, CWA has invested approximately $45.1 million in the rehabilitation of approximately 62.1 miles of water main and the renewal of associated
valves, service lines, meters, and fire hydrants throughout its service area. These projects are designed to increase residual water pressures and
hydrant flows, decrease the incidence of pipe leakage, and improve water quality.
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