Coagulant and polymer chemicals are added to raw water entering the water treatment plant to increase the size of particles so they can be clarified and filtered. Injection of Alum and Polymer 1 occurs prior to the static mixer and Polymer 2 can be injected following the static mixer. Polymer 3 is injected in the TW pipe between the CAC discharges and the filter inlet box as a filter aid. For each of these chemicals there is a metering pump with capability of delivering variable feed rates. Each chemical is stored in 55-gallon drums or 275-gallon totes.
Control of the programmable chemical feed pumps is provided by the PCS and the Manufacturer supplied integral chemical feed pump controls. The chemical dosing may be manually adjusted at the PCS and is based on raw water and treated water turbidity analyzer data, pH analyzer data, and flow rate. The chemical feed rate is varied by pump stroke length and pulse frequency. Stroke length is a manual adjustment at the pump and pulse frequency is controlled by an analog signal input from the PCS.
Alum Pump Skid
Alum chemical feed pumps will have a pumping range of 0.001-1.9 gal/hr. The PCS will send RUN and frequency signals to the ALUM feed pump.
PCS Functions and Displays
The following functions and displays are available for the chemical feed pump operation at the PCS:
Alum
- Virtual HOA switch for each pump
- RUN indication for pump
- GENERAL FAULT indication for pump
- ETM for each pump
- Pulse frequency control for pump
- Calculated flow rate indication for each pump
- Start counts for pump
Polymer 1 Pump Skid
Polymer 1 chemical feed pumps will have a pumping range of 0.001-1.9 gal/hr. The PCS will send RUN and frequency signals to the Polymer 1 feed pump.
PCS Functions and Displays
The following functions and displays are available for the chemical feed pump operation at the PCS:
Polymer 1
- Virtual HOA switch for each pump
- RUN indication for pump
- GENERAL FAULT indication for pump
- ETM for each pump
- Pulse frequency control for pump
- Calculated flow rate indication for each pump
- Start counts for pump
Polymer 2 Pump Skid
Polymer 2 chemical feed pumps will have a pumping range of 0.001-1.9 gal/hr. The PCS will send RUN and frequency signals to the Polymer 2 feed pump.
PCS Functions and Displays
The following functions and displays are available for the chemical feed pump operation at the PCS:
Polymer 2
- Virtual HOA switch for each pump
- RUN indication for pump
- GENERAL FAULT indication for pump
- ETM for each pump
- Pulse frequency control for pump
- Calculated flow rate indication for each pump
- Start counts for pump
Polymer 3 Pump Skid
Polymer 3 chemical feed pumps will have a pumping range of 0.001-1.9 gal/hr. The PCS will send RUN and frequency signals to the Polymer 3 feed pump.
PCS Functions and Displays
The following functions and displays are available for the chemical feed pump operation at the PCS:
Polymer 3
- Virtual HOA switch for each pump
- RUN indication for pump
- GENERAL FAULT indication for pump
- ETM for each pump
- Pulse frequency control for pump
- Calculated flow rate indication for each pump
- Start counts for pump
Local Control:
The chemical feed pumps may each be operated in HAND mode. When HAND mode is selected on the integral pump control panel, the pump will operate according to manual settings available on the LCD display and local control panel face. In HAND mode, pump operation is independent of PCS control.
Local control of the chemical feed pumps is provided at local operator stations (LOSs) integral to the pumps. The LOSs will include LCD displays with programming keys, operating indicators, and fault indicators.
The following controls are provided on each of the LOSs:
- Integral display and keypad
- Virtual LOR switch (Local-Off-Remote)
- Stroke length adjustment knob
- RUN indication light (green) for each pump
- FAIL indication light (red) for each pump
- Calculated flow rate indication for each pump
- LOW pressure indication for each pump (i.e. leak detection system)
- ETM, stroke counter, dosing flow indication for each unit
- Communication FAIL (lost analog input)
PLC Control:
During normal operation, REMOTE is selected at the integral pump LOS and the PCS will control the chemical feed pumps by sending an analog 4-20mA signal for stroke pacing based on the current raw water pump rate. An operator adjustable dosing factor is adjusted to increase or decrease the overall chemical feed pump dose. Initial dosing ranges for the pumps are provided at start-up for scaling programming. The chemical pumps in in this mode of operation will start as soon as the raw water flow (FIT-100-2) is above the desired setpoint value.
Fail Signals:
Fail signals on the chemical feed pumps may be generated by a range of conditions including, but not limited to, low pressure indication, analog signals outside of programmed allowable values, pump overload, high temperature, dosing monitor is not correctly connected, broken diaphragm, and air lock. The fail conditions are programmable in the integral pump panel. All FAIL conditions will generate a General FAIL Alarm at the PCS.
If OFF is selected on the integral pump LOS, the PCS will generate a FAIL alarm if the chemical feed pump is not operating when called.
PLC / HMI Configuration:
- Status Display:
- Pump RUN/FAIL (each).
- Pump HAND / AUTO / OFF (each).
- Calculated pump flow rate (4-20 mA signal) (each).
- Pump ETM (each).
- Pump start counts (each).
- Ratio to influent flow (each).
- Operator Entries:
- Ratio to Influent Flow (4-20 mA signal proportional to stroke frequency).
- Alarms:
- GENERAL FAULT for each pump.
- Pump flow HIGH-HIGH ALARM (each).
- Pump flow HIGH ALARM (each).
- Pump flow LOW ALARM (each).
- Pump flow LOW-LOW ALARM (each).
- Historical Trending:
- Run counts (each).
- Current
- Yesterday
- Continuous
- Run counts (each).
- Start counts (each).
- Current
- Yesterday
- Continuous