EFFECTS OF CHLORIDE ON NITRIFICATION RATES
IN ACTIVATED SLUDGE SYSTEMS
Donald O. Hill, Assistant Professor
Civil Engineering Department
Mississippi State University
Mississippi State, Mississippi 39762
Stephen R. Gelman, Manager
Enviro-Labs, Inc.
Starkville, Mississippi 39759
INTRODUCTION
Saline wastewaters originate in several ways.  In some parts of the world, the scarcity
of fresh water has made the use of sea water for flushing necessary.   Similarly, many
shore-based industries and ocean-going vessels discharge wastewaters high in salinity.   Finally, saline wastewaters originate in several manufacturing processes, such as those found
in the cheese and pickle producing industries.   Although these industrial discharges are
not as high in chloride content as sea water, they contain considerably higher salinity
than typical domestic wastes.   Stricter laws concerning industrial as well as other waste
discharges have made the study of the treatment of saline wastewaters necessary.
In considering the treatment of wastewaters containing considerable salt content, attention must be given to the total pollutional loads being discharged into natural waters.
Not only must the carbonaceous biochemical oxygen demand (CBOD) and suspended
solids be considered in treatment objectives, but also the removal of unoxidized nitrogen,
measured as TKN, and phosphorous.   Frequently, the major oxygen demand exerted by
secondary plant effluents is caused by ammonia-nitrogen.   Therefore, many treatment
plants will have to be designed to accomplish nitrification.   As a result, information must
be available concerning nitrification rates in salt-water waste treatment systems.
The reaction kinetics for nitrification have been extensively studied and documented
for fresh water waste treatment systems.   However, the kinetics of biological nitrification
are not yet thoroughly understood, and a number of kinetic models have been proposed.
Each of these rate equations leads to a different set of design parameters for a reactor
of given treatment capacity.   Furthermore, little consideration has been given to the
effects of salt water on the nitrification process in an activated sludge treatment system.
The specific objectives of this research were as follows:
1. To develop a nitrification rate equation for the conditions studied.   Unlike expressing
the results as "percent remaining," the rate equation allows direct comparison for
any set of conditions.
2. To study the effects of varying salinity levels on nitrification in the activated sludge
process.
3. To determine the effect of temperature on the nitrification rate in salt-water
activated sludge.
4. To compare the nitrification rates in salt-water activated sludge with those obtained
in fresh water.
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