Biofilm Characteristics and Compositions in Fluidized Porcelanite Bioreactors: An Experimental Work

Abstract

Two systems of Fluidized Porcelanite Bioreactors (FPBR) were designed and constructed at Al-Rustamiyah Sewage Treatment Plant, South of Baghdad. The first system consists of Upflow Expanded Bed Reactor (UEBR) which is connected in sequence with aerated fluidized bed reactor (AFBR), while the other system is composed of two identical upflow expanded reactors operated in parallel. In order to evaluate the biofilm compositions and its characteristics on Porcelanite aggregates or fragment surfaces, an experimental measurements of the biofilm formation using the light microscopy in fixed media have been undertaken. Systems operation consists of various distinct phases, where influent substrate concentrations were taken from primary sewage and clarifier effluent of Al-Rustamiyah sewage.

Three effective parameters, that could influence the rate of biofilm growth such as superficial velocity, substrate, and biomass concentration, were investigated. The rate of biofilm was tested in two types of aeration; the first one was aerated directly compared with second one, which was operated by indirect aeration. Also the rate of biofilm losses for different influent flow rates, substrate concentrations, locations of packing bed in the reactor, and the periods of operation was evaluated. This work showed the main following conclusions:

1. The physical, chemical and biological analyses depend on the environmental conditions to which the attachment surface is exposed. The large portion of biofilm composition was water with 90.4%, and with a small value of volatile fraction ranged to 9.2%, while the fixed fraction is composed of 0.4% of total biofilm by mass.

2. Organic and chemical composition of the fixed fraction of biofilm was determined, where the primary constituents. carbon (C) was to be 58%, and nitrogen (N) to be 15%, and phosphorus (P) to be 2%, while the fixed solid composition was 25%.

3. The inorganic composition of fixed fraction of biofilm varies with chemical and organic properties of bulk water, chemical and physical properties of media, which composes mainly of silica with (45%), and with Fe $^{+2}$ (20%), Mn $^{+2}$ (14%), Al $^{+3}$ (10%), Ca $^{+2}$ (6%) and Mg $^{+2}$ (5%).