Environmental Engineering Reference
In-Depth Information
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effluent quality—
Poor-quality effluents have higher chlorine
demands, high concentrations of solids prevent chlorine-organism
contact, and incomplete nitrification can cause extremely high
chlorine demand.
•
mixing—
To be effective, chlorine must be in contact with the organ-
isms. Poor mixing results in poor chlorine distribution. Installation
of baffles and using a high length-to-width ratio will improve mix-
ing and contact.
•
Contact time—
The chlorine disinfection process is time dependent.
As the contact time decreases, process effectiveness decreases. A
minimum of 30 minutes of contact must be available at design flow.
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residual levels—
The chlorine disinfection process is dependent on
the total chlorine residual. The concentration of residual must be
sufficient to ensure that the desired reactions occur. At the design
contact time, the required minimum total chlorine residual con-
centration is 1.0 mg/L.
9.2.6.3 Process Control Sampling and Testing
The process performance evaluation is based on the bacterial con-
tent (fecal coliform) of the final effluent. To ensure proper operation of
the chlorination process, the operator must perform process control
testing for the chlorination process. Process control testing consists
of performing a total chlorine residual test on chlorine contact effluent.
The frequency of the testing is specified in the plant permit. The normal
expected range of results is also specified in the plant permit.
9.2.6.4 Troubleshooting
Following are common operational problems, symptoms, casual
factors, and corrective actions associated with chlorination system use
in wastewater treatment:
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symptom 1.
Coliform count fails to meet the required standards
for disinfection.
Cause:
Inadequate chlorination equipment capacity
Corrective action:
Replace equipment as necessary to provide
treatment based on maximum flow through the pipe.
Cause:
Inadequate chlorine residual control
Corrective action:
Use chlorine residual analyzer to monitor and
control chlorine dosage automatically.
Cause:
Short-circuiting in chlorine contact chamber
Corrective action:
Install baffling in the chlorine contact cham-
ber; install mixing device in chlorine contact chamber.
Cause:
Solids buildup in contact chamber
Corrective action:
Clean contact chamber.
