Developement of biological wastewater treatment procedures combining sequencing batch process and membrane technology

Biological treatment is the most economic way of treating wastewaters. Sequencing batch reactors (SBR) are one of the most successful means of achieving the desired treatment efficiency. Compared to conventional technology SBR uses much less reactor volume to achieve the same treatment efficiency or to produce higher biogas yield per reactor volume. SBR can be operated at higher active biomass concentration and therefore it may achieve even higher treatment efficiencies. The main problem is that the settling phase of SBR is not efficient enough at higher biomass concentrations; therefore, the biomass may leak of the system. The solution to this problem is the proposed hybrid system of SBR and membrane technology that may offer very good results in treatment and containment of biomass in the reactor. To achieve this objective we will study the kinetics of SBR process at higher biomass concentrations. We will monitor and study the enzyme reactions in the biomass/wastewater suspension in order to determine the response to potential toxic substances in industrial wastewaters and slurries. After determining the enzyme reactions and responses, we will try to adopt the biomass to accept the toxic substances to the level of successful degradation or successful biogas production. In the systems with anaerobic SBR (ASBR) the main emphasis will be in the effective biogas production, what will consequently show in reduced emissions in industrial production processes as well as in higher percentage of renewable energy in Slovenia. We will also study the membrane part of the treatment technology. We will determine the most appropriate floccules size for successful log-term filtration in consideration of good settling properties of the floccules. We will study the materials of membranes in combination with floccules size in order to prevent membrane fouling and assure undisturbed operation of the system. After determining optimal conditions for the hybrid SBR – membrane process, we will design and construct a pilot plant (in cooperation with the beneficiary), that will serve as a model for successful marketing of the process. Beneficiary is entering the project with intention that the developed process will be successfully marketed product worldwide.

Microbial aggregation process discovered in the SBR systems draw attention to the likelihood of physical and/or chemical stress factors to trigger microbial responses resulting in a shift from dispersive to aggregative physiology. Systems with granulated sludge must be studied both from a microbiological and from an engineering stand-point (for example: the hydrodynamic shear experienced by microorganisms in activated sludge systems and correlation between application of of high shear in terms of superficial upflow air velocity and mechanical mixing and initiation, formation and stability of anaerobic and aerobic granules). The active material in “nanofilters” is nanoalumina fibres with dense electropositive charges. Having the features of both electrical and mechanical media “nanofilters” bring new capability to water filtration. As a general rule all particles tend to become more electronegative as the particle size diminishes. Therefore filtration efficiency of “nanofilters” improve against ever finer particles. Varying removal capability for dissolved metals (Fe, Zn, As) was also demonstrated in our laboratories. Studying anaerobic processes we have deiscovered that granulated biomass can treat wastewaters with higher concentrations of suspended solids. In recent scientific reports it is stated that granulated biomass can treat only low concentrations of suspended solids. This is due to the fact that only flow through systems have used granulated biomass. We used granulated biomass in a sequencing batch reactor and have managed to prove that it is possible to treat higher concentrations of suspended solids with granulated biomass. This fact opens a variety of treatments for waste substrates which have not had a suitable treatment option.

Results of our experiments in biological wastewater treatment and sludge treatment show that the efficiency of the biological wastewater treatment in the SBR can be increased with the partial granulation of the activated sludge. The quality of treated water could be increased and the production of the excess sludge decreased, respectively. Production of the biogas could be increased and the final volume of excess sludge could be decreased substantially. “Nanofilters” are used for the treatment of drinking water in domestics households. Treatment of the industrial wastewaters with “nanofilters” could increase the amount of water which could be re-used in the production process especially in the cases of the great sensitivity of the systems to the presence of microorganisms in the water. Anaerobic processes developed in this project will help increase renevable energy use (carbon footprint reduction) in industrial processes, where large ammounts of wastewater and other organic wastes are generated. Most interest was already expressed by brewing and beverage industry (although they did not participate directly in this project) to implement the technology developed in this project.