Date of Award

Summer 1992

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Civil, Construction, and Environmental Engineering

First Advisor

Zanoni, A. E.

Second Advisor

Novotny.

Third Advisor

Crandall, Clifford J.

Abstract

A number of paper mills produce effluents with BOD5 values in the range of 30-100 mg/I. These are considered low strength wastes, especially when biological treatment is to be provided. To further reduce BOD5, the conventional activated sludge process is considered uneconomical as the F/M ratio is quite low. Operation of such a process needs extended aeration, consuming excess electrical energy. In this case, the attached growth process is considered as an alternative to the activated sludge process. A ''Tower Filter" with plastic media is proposed for treating low strength paper mill wastes. However, it is not known if the attached growth system has the same capacity to reduce toxicity as exhibited by the activated sludge process. The present study included a literature review covering the application of the trickling filter to low strength wastes for B0D5 and toxicity reduction. Also included was an evaluation of the attached growth process for toxicity reduction using a pilot trickling filter plant in the laboratory. A synthetic paper mill wastewater consisting of starch, tissue paper, fuller's earth and nutrients was used as a low strength test substrate. Several chemicals commonly used in the paper industry were added to produce toxicity in the synthetic wastewater. The toxicity reduction was evaluated by conducting bioassays on the influent and effluent. The study showed that the trickling filter (attached growth process) can reduce toxicity an order of magnitude beyond the LC50 value without affecting the BOD5 removal. However, when the toxicity was increased to higher concentrations (much beyond the LC50), the bio-mass is stressed resulting in lower BOD5 and toxicity removal.

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