Masters Theses

Debby Hines

Date of Award

6-1981

Degree Type

Thesis

Degree Name

Master of Science

Major

Environmental Engineering

Major Professor

Dennis W. Weeter

Committee Members

Roger A. Minear, Gary Sayler

Abstract

A study was conducted to examine the production of ammonia in a packed-bed anaerobic upflow (ANFLOW) bioreactor which uses fixed-films of microorganisms. ANFLOW bioreactors have been under development as innovative alternative wastewater treatment systems. Domestic waste-water contains proteins from the wastes of humans and animals; as the amino acids from the proteins break down, there is formation of ammonia, volatile fatty acids, and other products. Under anaerobic conditions, proteinaceous material is converted to volatile fatty acids by a complex group of bacteria; the volatile acids are then reduced to methane by specialized methanogenic bacteria which are very sensitive to environmental conditions. The methane gas may be collected and utilized for energy. Some of the ammonia is used in cell synthesis but there is a net accumulation of ammonia in the system because the rate of cell growth of the methanogens is slow.

A synthetic organic waste feed was used containing glucose (as a carbon source), nutrient broth (as a protein and trace mineral source), and sodium bicarbonate (for alkalinity). Three concentrations of soluble chemical oxygen demand (SCOD) and two hydraulic loading rates (HLR) were used resulting in a three-by-two experimental matrix design.

Gas production, percentage methane of the off-gas, pH, alkalinity, volatile acids, and SCOD were used to monitor perturbations of steady-state conditions. Nitrogen mass balances were determined by analyzing total Kjeldahl nitrogen (TKN), nitrate+nitrite-nitrogen, and ammonia-nitrogen.

Removal rates of SCOD ranged from 87-95% within the ANFLOW bioreactor. The most efficient SCOD removal occurred at the highest organic loading rate (OLR). Profiles of SCOD and volatile acids concentrations showed distinct regions of complex organics breakdown and wastes stabilization. Hydraulic flow within the ANFLOW bioreactor behaved approximately as in a plug-flow reactor (PFR).

The effluent ammonia concentration appeared to be a function of HLR. For a given OLR or influent SCOD, effluent ammonia concentrations were less at the higher flow rate. These results suggest that at the shorter hydraulic residence time (HRT), there was less time for ammonia accumulation and conversion of organic-nitrogen to ammonia-nitrogen could not be fully completed. However, overall ammonia-nitrogen formulation (in terms of grams per day produced) was found to be linear as a function of OLR. The figures presented could be used for predicting effluent ammonia concentration for a given OLR, HLR, or SCOD, or ammonia formation for a given OLR.

It was demonstrated that the ammonia can be nitrified using an aerobic, upflow packed-bed bioreactor with only 5% volume of the ANFLOW bioreactor and a hydraulic residence time of only a few hours. A series of packed-bed bioreactors was recommended for carbon removal/waste stabilization--ammonia removal--denitrification. The methane gas produced could be used for power requirements.

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