Title

16 Sodium Hypochlorite System - Loss of Disinfection

Addressing the loss of disinfection is generally a series of troubleshooting activities and corrective actions. Typical causes of a loss of disinfection include the following:
  • Loss of prime at the pump due to  trapped air in the piping or low chemical level in the supply tank
  • Incorrect valve status
  • Broken piping

Once the system is functioning properly, normal operation of the system should be apparent at the SCADA workstation.

 

The Sodium Hypochlorite System is comprised of seven chemical feed pumps, each with a specific function, as briefly described below.

  • Pump No. 1 & No. 2: Post chlorination. 
  • Pump No. 3: Pretreatment Chlorination at the confluent or temporary back up for Pumps No. 1 and No. 2
  • Pump No. 4: RS chlorination, temporary use to combat high SVIs, bulking or bad settling in the clarifiers
  • Pump No. 5: Pre-chlorionation at the tertiary filters during the backwash cycle
  • Pump No. 6 & No. 7: Provides the required chlorine residual at the CCBs for the Reclaimed Water System.
  • Pump No. 3 can be used on a temporary basis as a back up for Pump No. 1 or No. 2. Pump No. 3 is smaller, however, and can only provide 25 – 30 gpm (which is typically not enough for continued disinfection).
The lead/lag status of Pumps No. 1 and No. 2 and Pumps No. 6 and No. 7 are manually rotated on a monthly basis at SCADA.
SOP Identification Number
SOP Identification Number:
1604_Sodium Hypochlorite System - Loss of Disinfection
Purpose and scope
Purpose and scope:

DIsinfection is required to meet the permit limits.

Definitions
Definitions:

CCB: Chlorine Contact Basin

Health & Safety Warnings
Health & Safety Warnings:

Any loss of disinfection is to be immediately reported to a Supervisor. Any loss in disinfection could be a potential permit violation that must be reported to the appropriate regulatory agencies.

Cautions
Cautions:
  • Ensure that adequate chemical supply is on hand.
Procedure
Procedure:
1.     Chemical Tanks (Troubleshooting & Corrective Action):
a.     Check valve status to ensure a chemical supply to the pump suction header. 
b.     Open the draw down tube at each pump to bleed off air. 
c.     Verify that the in service tank has a sufficient chemical level to maintain a prime at the in service chemical pump. Switch tanks if necessary by manually opening and closing the tank discharge valves. The tank in service must have a liquid level that is higher than the suction. The swing shift operators check tank levels each day.
 
2.     Chemical Pumps (Troubleshooting & Corrective Action):
a.     Increase pump speed and stroke at the SCADA workstation to a higher than normal level. Leave in place long enough to resume prime.  Reset to normal pump speed and stroke after the pump returns to normal operation.
b.     Connect the garden hose to the provided connection port for the in-service pump. Make sure the hose is securely connected before opening the isolation valve to the suction headers {tag no. 1604VLV6100B, 1604VLV6200B, 1604VLV6300B, 1604VLV6400B, 1604VLV6500B, 1604VLV6600B, 1604VLV6700B}. Turn on the water supply to the garden hose. Close the pump suction valve. When prime is restored, open the pump suction valve and turn off the garden hose. 
 
3.     Chemical Piping & Valves (Troubleshooting & Corrective Action):
a.     Check valve status on the in service pump to ensure that discharge piping is open. 
b.     Remove trapped air from the system by opening the bottom of draw down tube. Let air escape and close the pump suction valve. Once the air is purged, close the draw down tube and reopen the pump suction valve.
c.     Check for breaks in the exposed chemical suction and discharge piping. Also, check the piping in the adjacent vault and under the stairs at the Chlorine Contact Tank. If a line break is discovered, immediately notify the supervisor and repair the break.
d.     Air can build up in the chemical piping while a pump is offline. This air needs to be purged from the system before that pump is rotated back into service.
Equipment
Equipment:
Equipment Name
Tag Number
Pump No. 1 - Post Chlorination
1604PMP/MTR6100
Pump No. 2 - Post Chlorination
1604PMP/MTR6200
Pump No. 3 - Pretreatment Chlorination
1604PMP/MTR6300
Pump No. 4 - RS Chlorination  
1604PMP/MTR6400
Pump No. 5 – Filter Pre-Chlorination
1604PMP/MTR6500
Pump No. 6 – Reclaimed Water Chlorine Residual
1604PMP/MTR6600
Pump No. 7 – Reclaimed Water Chlorine Residual
1604PMP/MTR6700
Tank No. 1
1604TNK6692
Tank No. 1 Discharge Valve
1604VLV6692B
Tank No. 1 Level Sensor/Transmitter
1604LE/LIT/LI6541
Tank No. 2
1604TNK6693
Tank No. 2 Discharge Valve
1604VLV6693B
Tank No. 2 Level Sensor/Transmitter
1604LE/LIT/LI6542
Tank No. 3
1604TNK6694
Tank No. 4 Discharge Valve
1604VLV6694B
Tank No. 3 Level Sensor/Transmitter
1604LE/LIT/LI6543
Suction Header Isolation Valve – Pump No. 1
1604VLV6100B
Suction Header Isolation Valve - Pump No. 2
1604VLV6200B
Suction Header Isolation Valve – Pump No. 3
1604VLV6300B
Suction Header Isolation Valve – Pump No. 4
1604VLV6400B
Suction Header Isolation Valve – Pump No. 5
1604VLV6500B
Suction Header Isolation Valve – Pump No. 6
1604VLV6600B
Suction Header Isolation Valve – Pump No. 7
1604VLV6700B
ID
Maintenance Connect