Date of Award

12-1993

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Mohamed Fathy Hamoda

Second Advisor

Dr. Mohamed Sorour EI-Shahawi

Third Advisor

Dr. Saad Al Numairy

Abstract

The wastewater treatment plant in Dubai, with a design capacity of 130,000 m3/d, receives primarily domestic wastewater and employs primary, secondary and tertiary stages of treatment to produce an effluent suitable for reuse in irrigation. Performance of the plant is influenced to a great extent by the success of the secondary aerobic biological treatment stage. This stage comprises the high-rate activated sludge system for removal of carbonaceous organics followed by the biofilter system for removal of nitrogenous material by nitrification. Operational problems have often been experienced at this plant because of increasing sludge solids production and sludge rising in the high-rate activated sludge system, which in turn overload the sludge treatment facilities and the biological filter system. This study aimed at upgrading the existing biological treatment system in an attempt to improve process performance and overcome operational problems. An innovative biological system, the aerated submerged fixed-film (ASFF) process which employs a four compartment-in-series reactor with an array of fixed ceramic plates, has been examined for this purpose.

The study involved field testing and chemical analyses of a pilot-scale ASFF bioreactor in a series of experiments on the ASFF reactor in parallel with the existing activated sludge and biofilter systems. Performance of the ASFF process was examined at different hydraulic retention times (HRT's) and loading conditions. The results obtained demonstrated the feasibility of upgrading the existing facilities by the ASFF process. Analysis of performance data indicated comparable results at short HRT's of 2 hours and considerably better results from the ASFF at longer HRT's of 6-8 hours. The ASFF process has an advantage of combining the removal of both carbonaceous and nitrogenous materials in one system rather than in two systems as practiced in the existing facilities. This process requires less space and produces minimal sludge solids quantities, thus reducing the treatment costs. It will provide an adequate treatment that does not suffer from the rising sludge problem and can easily cope with overloading as long as sufficient aeration is provided. The process can be easily implemented in the aeration tanks of the existing activated-sludge system by fixing an array of locally-made ceramic plates which will also eliminate the need for biofilters. A mathematical model was adopted to describe process kinetics and to design the upgraded system.

Download
COinS