Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

William A. Weiler


In pure cultures of Nitrosomonas, copper is known to cause a stimulation of nitrification at low levels (≤ 0.03 mg Cu+2/1) and an inhibition affect at higher levels (≥ 0.05 mg Cu+2/1). Nitrifying activated sludges are much more tolerant of copper showing only 75% inhibition at 150mg Cu+2/1. The purpose of this paper was to determine the copper sensitivity of a nitrifying biofilm grown in a continuous flow trickling filter system.

A continuous flow trickling filter system was built using limestone chips for the biofilm substrate. The biofilm was established from secondary effluent. After 1 month, a stable nitrification rate of 4 mg NO3-N/1/hr was obtained at a flow rate of 13.9 1/hr. A synthetic medium was then introduced and pH was stablized (6.5 - 7.5) with a polystaltic pump buffer drip system for the rest of the study.

Inhibition studies at various copper levels (0.005 - 1.0 mg/1 Cu+2 were initiated. Copper was introduced for 12 hours, the column was drained, flushed with new synthetic medium, and refilled with three liters fresh medium. Nitrification rate (mg NO3 -N/1/hr) was monitored every 4 hours for 60 hours or until a return to the basal rate (12 - 14 mg NO3-N/1/hr) was noted. A peak nitrification rate occurred 12 hours after introduction of the stimulatory level of 0.10 mg Cu +2/1. At the copper level of 1.0 mg Cu+2/1, an immediate (90%) inhibition was apparent.

The nitrifying biofilm response to copper was comparable to that of pure cultures of Nitrosomonas and much more sensitive than that which was reported for the nitrifying sludges.