Michal Dohanyos

Enhanced biogas yield from energy crops with rumen anaerobic fungi

Anaerobic fungi (AF) are able to degrade crop substrates with higher efficiency than commonly used anaerobic bacteria. The aim of this study was to investigate ways of use of rumen AF to improve biogas production from energy crops under laboratory conditions. In this study, strains of AF isolated from feces or rumen fluid of cows and deer were tested for their ability to integrate into the anaerobic bacterial ecosystem used for biogas production, in order to improve degradation of substrate polysaccharides and consequently the biogas yield. Batch culture, fed batch culture, and semicontinuous experiments have been performed using anaerobic sludge from pig slurry fermentation and different kinds of substrates (celluloses, maize, and grass silage) inoculated by different genera of AF. All experiments showed a positive effect of AF on the biogas yield and quality. AF improved the biogas production by 4–22%, depending on the substrate and AF species used. However, all the cultivation experiments indicated that rumen fungi do not show long‐term survival in fermenters with digestate from pig slurry. The best results were achieved during fed batch experiment with fungal culture Anaeromyces (KF8), in which biogas production was enhanced during the whole experimental period of 140 days. This result has not been achieved in semicontinuous experiment, where increment in biogas production in fungal enriched reactor was only 4% after 42 days.

Potentials and limits of anaerobic digestion of sewage sludge: energy self-sufficient municipal wastewater treatment plant?

Anaerobic digestion is the only energy-positive technology widely used in wastewater treatment. Full-scale data prove that the anaerobic digestion of sewage sludge can produce biogas that covers a substantial amount of the energy consumption of a wastewater treatment plant (WWTP). In this paper, we discuss possibilities for improving the digestion efficiency and biogas production from sewage sludge. Typical specific energy consumptions of municipal WWTPs per population equivalent are compared with the potential specific production of biogas to find the required/optimal digestion efficiency. Examples of technological measures to achieve such efficiency are presented. Our findings show that even a municipal WWTP with secondary biological treatment located in a moderate climate can come close to energy self-sufficiency. However, they also show that such self-sufficiency is dependent on: (i) the strict optimization of the total energy consumption of the plant, and (ii) an increase in the specific biogas production from sewage sludge to values around 600 L per kg of supplied volatile solids.

Combined anaerobic treatment of wastewaters and sludges

One of the most recent and progressive reactor principles used in anaerobic wastewater treatment technology is a vertical compartmentalization, which is used in the USSB (Upflow Staged Sludge Bed) reactor. Thanks to its specific design and features the operation of such a reactor can be very flexible. Examples are given showing tested alternatives of operation with combined wastewater and sludge treatment. A high treatment efficiency and a very low specific sludge production was achieved with the operation of a technological system consisting of a USSB reactor and an aerobic biofilm reactor. In the USSB reactor wastewater and surplus sludge treatment can not only be combined but also anaerobic pretreatment and biological denitrification.

The influence of anaerobic pretreatment on the nitrogen removal from biosynthetic pharmaceutical wastewaters

The C:N ratio of the pharmaceutical wastewaters is usually suitable for a combination of the anaerobic pretreatment with the high COD removal and aerobic posttreatment with the efficient biological N removal. This kind of anaerobic-aerobic process was tested in semipilot scale by using a UASB reactor and an activated sludge system with a predenitrification (total volume 100 1). It was found that at a total HRT of 2.3 days an average of 97.5% of COD and 73.5% of total N was removed. The UASB reactor was operated at 30°C with a volumetric loading rate of 8.7 kg.m-3.d-1, the efficiency of COD removal was 92.2%. The processes, which take part in the biological removal of nitrogen, especially the nitrification, were running with lower rates than usually observed in aerobic treatment systems.

Impact of accelerated electrons on activating process and foaming potential of sludge

Abstract The process of activation is an important part of wastewater treatment technology. It can be affected in many ways, not least by using radiation. The paper describes effects of pre-irradiation of small part of biomass on activated sludge process. It has been shown, that relatively low dose of accelerated electrons can positively affect many parameters of the system.

ANAEROBIC TREATMENT OF DISTILLERY SLOPS IN THE CIRCUMSTANCES OF CENTRAL EUROPE

Anaerobic treatment of many kinds of slops is one of the most progressive ways for the reuse of this material. The special feature of Central Europe is that the largest proportion of ethanol is produced by fermentation, and the raw material in big distilleries is only sugar beet molasses. The consequence of this is a large production of slops in small regions, and as far as the quality of slops is concerned, a relatively high content of inert and nonbiodegradable organic compounds in comparison with other more valuable raw materials, such as grapes, fruits, cereals, potatoes, etc. A two-year operation of the pilot scale UASB reactor bas shown that molasses slops are a suitable material for anaerobic treatment The slops were diluted by other wastewaters from the distillery to a concentration of about 25 g.l ‒1 COD and then treated in the pilot reactor at 32°C with the following average results: COD removal efficiency 78.8 %; volumetric loading rate 7.1 kg.m-3.d ‒1 ; volumetric gas production 2.6 m 3 .m ‒3 .d ‒1 ; specific gas production 0.47 m 3 .kg ‒1 . The results achieved confi11II that molasses slops are a source of energy. For example, Czech distilleries could potentially produce 12-17 million m3 of the valuable gas fuel per annum.