Improving the effects of hydrolysis on waste activated sludge (WAS) prior to anaerobic digestion is of primary importance. Several technologies have been developed and partially implemented in practice. In this paper, perhaps the simplest of these methods, alkaline solubilization, has been investigated and the results of hydrolysis are presented. An increase to only pH 8 can distinctively increase the soluble chemical oxygen demand (SCOD), and produce an anaerobic condition effect favorable to volatile fatty acids (VFA) production. Further increases of pH, up to pH 10, leads to further improvements in hydrolysis effects. It is suggested that an increase to pH 9 is sufficient and feasible for technical operations, given the use of moderate anti-corrosive construction material. This recommendation is also made having taken in consideration the option of using hydrodynamic disintegration after the initial WAS hydrolysis process. This paper presents the effects of following alkaline solubilization with hydrodynamic disintegration on SCOD
Anaerobic digestion residue represents a nutrient rich resource which, if applied back on land, can reduce the use of mineral fertilizers and improve soil fertility. However, dewatering and further thermal processing of digestate may be recommended in certain situations. Limited applicability of digestate as fertilizer may appear, especially in winter, during the vegetation period or in areas where advanced eutrophication of arable land and water bodies is developing. The use of digestate may be also governed by different laws depending on whether it is treated as fertilizer, sewage sludge or waste. The aim of this paper is to present the effects of thermal treatment of solid fraction of digestate by drying followed by pyrolysis and gasification. Pyrolysis was carried out at the temperature of about 500°C. During this process the composition of flammable gases was checked and their calorific value was assessed. Then, a comparative analysis of energy parameters of the digestate and the carbonizate was performed. Gasification of digestate was carried out at the temperature of about 850°C with use of CO2 as the gasifi cation agent. Gasification produced gas with higher calorific value than pyrolysis, but carbonizate from pyrolysis had good properties to be used as a solid fuel
Primary or secondary sewage sludge in medium and large WWTP are most often processed by anaerobic digestion, as a method of conditioning, sludge quantity minimization and biogas production. With the aim to achieve the best results of sludge processing several modifications of technologies were suggested, investigated and introduced in the full technical scale. Various sludge pretreatment technologies before anaerobic treatment have been widely investigated and partially introduced. Obviously, there are always some limitations and some negative side effects. Selected aspects have been presented and discussed. The problem of nitrogen has been highlighted on the basis of the carried out investigations. The single and two step - mesophilic and thermophilic - anaerobic waste activated sludge digestion processes, preceded by preliminary hydrolysis were investigated. The aim of lab-scale experiments was pre-treatment of the sludge by means of low intensive alkaline and hydrodynamic disintegration. Depending on the pretreatment technologies and the digestion temperature large ammonia concentrations, up to 1800 mg NH4/dm3 have been measured. Return of the sludge liquor to the main sewage treatment line means additional nitrogen removal costs. Possible solutions are discussed.
The aim of the conducted research was to determine the possibilities of using the biomass of macroalgae obtained from Puck Bay during May-September season in biogas production process. Model respirometry chambers were used to determine the amount of produced biogas and examine its quality composition. Depending on the month in which the algal biomass was obtained, the experiments were divided into five stages. In each stage, the effectiveness of the biogas production process was tested for the applied loads in model fermentation chambers in the range from 1.0 kg DOM/m3 · d to 3.0 kg DOM/m3 · d. During the experiments it was found that the efficiency of biogas production varied from 205 dm3/kg DOM to 407 dm3/kg DOM depending on the month of the vegetation season and the applied organic matter load in the chamber. Methane content was very high and ranged from 63% to 74%.
This paper presents the results of fractionation of particulate and soluble organic matter in a mixture of maize silage and cattle manure (49:51% volatile solids) that was used as a feedstock for anaerobic digestion. The extended Weender’s analysis was adapted to measure raw protein, raw lipids, fraction of carbohydrates (including starch, cellulose, hemicelluloses) and lignin. The content of individual fractions in composite, Xc (as kg COD kg-1 COD) was: 0.111 proteins, 0.048 lipids, 0.500 carbohydrates and 0.341 inerts. The biodegradability of Xc was 68%. Based on material balance, the carbon concentration in Xc was 0.0326 kmol C kg-1 COD, whereas nitrogen concentration 0.0018 kmol N kg-1 COD. The estimated pH of the feedstock based on acid-base equilibrium corresponded to the actual value (pH 7.14).
The aim of this study was to implement ADM1xp model to simulate behavior of anaerobic co-digestion of maize silage and cattle manure. The accuracy of ADM1xp has been assessed against experimental data of anaerobic digestion, performed at OLR = 2.1 gVS dm-3·d-1 and HRT = 45d. Due to the high number of parameters in ADM1xp, it was necessary to develop a customized procedure limiting the range of parameters to be estimated. The best fitting of experimental to simulated data was obtained after verification of 9 among 105 stoichiometric and kinetic parameters. The values of objective function (Jc) ranged between 0.003 (for valerate) and 211 (for biogas production).
The aim of the study was to develop an effective treatment of post-digestion liquors highly-loaded with biogenic and organic substances. The scope of the research project encompassed: mesophilic anaerobic digestion of waste activated sludge (WAS) as well as the treatment of post-digestion liquors, coming from the most appropriate HRT value of 25 days, in the process of ammonium magnesium phosphate (struvite) precipitation targeted at ammonia nitrogen binding and a subsequent reverse osmosis (RO) process. It was established that the method combining chemical precipitation and high-pressure filtration ensures a high degree of contaminants removal allowing for a direct release of treated liquors into the natural reservoir. However, in order to decrease the residual NH4+ concentration (6.1 mg NH4+/dm3) in the purified post-digestion liquors below the level allowing for a direct release to the natural reservoir, it turned out to be necessary to apply increased molar ratio of magnesium and phosphates (Mg:NH4+: PO43-= 1.5:1:1.5).
The substrates to biogas production in anaerobic digestion, except plant materials, can also be animal feces and manure. It should be highlighted that Poland is one of leaders in the European Union in animal breeding. However, there is no precise data in the literature on the potential of biogas production from animal feces in this country. The aim of the paper was to analyze the biogas production potential from manure in Poland. The aim of work included anaerobic digestion research following materials: cow manure, pig manure, poultry manure and sheep manure. In the next step, based on the obtained results of the biogas yield, energy potential calculations were made. The methane yield for the investigated feedstock materials in the batch culture technology was performed following the internal procedures developed based on the adapted standards, i.e. DIN 38 414-S8 and VDI 4630. Animal wastes were obtained from the Agricultural Experimental Stations of Poznan University of Life Sciences (Poznan, Poland). On a base of achieved results it was concluded that tested substrates have a high energy potential (approx. 28.52 GWh of electricity). The largest potential for electricity production was found in chicken manure (about 13.86 GWh) and cow manure (about 12.35 GWh). It was also shown which regions of Poland have the best chance for development of agriculture biogas plants (Wielkopolskie and Mazowieckie voivodships) and where the potential is the least (Lubuskie and Opolskie voivodeships).
The potential of organic wastes in Ukraine for biogas production and the prospects of using the family-type biogas plants for this purpose are shown. In the biogas laboratory of the Ukrainian National Forestry University the efficiency of the anaerobic mesophilic digestion of chicken manure of Poltava poultry farm, Kamianets-Podilsky poultry farm and sewage sludge from Lviv wastewater treatment plant (WWTP) was investigated. Different integral indicators of the biogas production and significantly different dynamics of its formation over time were obtained for three investigated substrates. The value of average specific biogas production from the sewage sludge of Lviv WWTP is 0.494 dm3∙(day∙kg FM)–1, which is 5.1 times more comparing the chicken manure of Kamianets-Podilsky poultry farm and 8.0 times more than for the chicken manure of Poltava poultry farm. Strong negative effect of antibiotic treatment of chickens on methane contentin the obtained biogas was established experimentally.
Anaerobic digestion (AD) is an adequate alternative to treat wastewater generated from fruit and vegetable processing (FVWW); likewise, in recent years, artificial wetlands (AWs) have been applied as a post-treatment process for anaerobi-cally pre-treated wastewater. The objective of this work was to design a sustainable treatment system for FVWW composed of upflow anaerobic reactors (UASB) with phase separation and an AW system that receive the anaerobically pretreated effluent. Using the design methodologies for the UASB reactors and artificial wetlands with sub-surface flow (AW-SSF), the parameters of the combined AD-AW system that treat a wastewater flow of 300 m3∙d–1 were calculated. The UASB acidogenic system was adjusted to a hydraulic retention time (HRT) of 10 h and organic loading rate (OLR) of 13.84 kg COD m–3∙d–1; meanwhile, the methanogenic and cascade UASB reactors with OLRs of 10.0 and 3.0 kg COD m3∙d–1, and HRTs of 11 and 10 h, respectively, achieve a high COD removal efficiency (above 94%), and an overall biogas production rate of 1.53 m3 of biogas per m3 of reactor capacity per day. According to the results obtained with the theoretical design, anaerobic-wetland combined system achieves an overall efficiency greater than 98%. The wastewater treated by the pro-posed system will allow the reuse of 30% of the water used in the washing of fruits and vegetables.