TOTAL DISSOLVED SOLIDS EFFECTS ON BIOLOGICAL TREATMENT
M. R. Hockenbury, Project Manager
D. Burstein, Design Manager
Engineering-Science, Inc.
Atlanta, Georgia 30329
E. S. Jamro, Environmental Engineer
Monsanto Company
St. Louis, Missouri 63166
INTRODUCTION
Operating biological treatment systems in high (2 to 5%) and/or rapidly changing
total dissolved solids (TDS) environments can create significant industrial waste treatment
problems.   Studies have shown that high TDS concentrations and TDS shocks have a
negative effect on systems treating municipal wastes [1-5].   However, few investigations
concerning TDS effects on industrial waste treatment systems have been published.   This
lack of information may hinder industries with high TDS wastes from perceiving effluent
discharge problems prior to operating a treatment system which will experience high
and/or changing TDS concentrations.
LITERATURE REVIEW
Studies by Lawton and Eggert [ 1 ] indicated that trickling filter slimes experiences
very low BOD removals when wastes containing greater than 20,000 mg/1 TDS were
applied or when a system acclimated to TDS concentrations in excess of 20,000 mg/1
was subjected to essentially TDS-free waste.   At the high TDS level with a 1-day partial
recovery, slime growth was slight and BOD removal was still lower than that found in
the low TDS environment.   In a similar study on percolating filters, Mills and Wheatland
[2] found that 6,600 mg/1 sodium chloride added continuously produced no upset performance.   However, an increase in sodium chloride from 6,600 mg/1 to 20,000 mg/1
caused some loss of efficiency.
Stewart, Ludwig and Kearns [3] studied the effects of varying salinity (TDS) on the
extended aeration process to ascertain the ability of this system to treat shipboard wastes.
While temporary impairment of treatment efficiency (i.e., higher effluent suspended
solids and BOD) was noted as TDS concentrations varied, the authors concluded that at
normal hydraulic and organic loads, severe TDS changes would not significantly impair
process effluent quality.
Burnett [4] found that alternating shocks of freshwater sewage and highly saline
(80% seawater) sewage severely disrupted treatment efficiency.   BOD removals of 80%
or greater were obtained in the highly saline sewage but not maintained during shock
loads.
Studies were conducted by Ludzack and Noran [5] on activated sludge and on anaerobic digester performance.   When increasing from 100 mg/1 up to 20,000 mg/1 chlorides,
the activated sludge system had higher effluent suspended solids and BOD, and nitrification
was reduced by 90%.   The anaerobic digester was more severely affected by high chlorides.
It produced from 20-50% less gas at the 20,000-mg/l chloride level.
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