Operations of Experimental Trickling
Filters on Oil-Containing
Waste Waters
R.   J.  AUSTIN, W.   F.  MEEHAN,  and  J.  D.  STOCKHAM
Group Leader, Assistant Superintendent of
Technical Service, and Chemist
Standard Oil Company
Whiting, Indiana
Oil-containing waste waters from petroleum refineries are normally
discharged through gravity-type oil-water separators (4). Under many
conditions, however, oil-water mixtures contain emulsions and solids that
retard gravity separation, and minute particles of oil and solids remain
in suspension in the discharge from the separator. Oil itself is slightly
soluble in water. These suspended and dissolved materials impart tastes
and odors to the discharge and are responsible for the oxygen demand.
Studies have been undertaken to develop treatment processes that will
economically remove the materials producing tastes and odors and will
reduce the oxygen demand of refinery waste waters.
Such biological processes as the trickling-filter and the activated-
sludge process have proved effective in the treatment of many industrial
waste waters (7). Both of these processes provide an aeration or oxidizing zone, where the waste water and microorganisms are contacted,
and clarifiers or final settling tanks. Trickling filters employ a stationary
biological system, the microorganisms being contained in the slime that
envelops the filter medium. The activated-sludge process employs a circulating biological system, the sludge acting as the carrier for the
microorganisms. The activated sludge is separated from the treated
waste water in the settlers and all or a suitable portion is returned to
the oxidizing zone where it is mixed with the incoming waste water.
In both processes, the decomposable organic matter in a waste is oxidized or metabolized in the aeration zone, and the insoluble matter
generated as a result of biological reactions are removed in the settlers.
In the present study, the trickling filter was chosen for the treatment of gravity-separated refinery process water because of its stability
and low operating costs. The effectiveness was investigated in pilot-
scale equipment over a test period of 17 consecutive weeks.  The criteria
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