CO-DIGESTION OF SEWAGE SLUDGE AND MATURE LANDFILL LEACHATE IN PRE-BIOAUGMENTED SYSTEM

The study examined the effects of co-digestion of sewage sludge and mature landfill leachate at the volumetric ratio of 95:5% in primarily bioaugmented system. Bioaugmentation was carried out with the use of commercial product Arkea® in the volumetric dose of 5% and lasted three months prior to the co-digestion start-up. Co-digestion was undergone without bioaugmentation. The results indicated that in the first period (of three months) following bioaugmentation, co-digestion led to biogas/methane yields only 5-8% lower as compared to anaerobic digestion of sewage sludge, and the differences were not statistically significant. Moreover, a comparable value of volatile solids removal was obtained. However, the effects became worse over time, i.e. a lower organics removal efficiency of 16% as well as 9.5–13% decreases of biogas/methane yields were achieved by applying co-digestion for a further period (of the same duration). Co-digestion of sewage sludge and mature landfill leachate could be recognized as quite efficient in the system that was primarily bioaugmented with the use of Arkea®. However, the beneficial impact of bioaugmentation remained for the limited period of three months after its completion. To sustain the favourable effects a periodical, repeatable bioaugmentation of the co-digestion system is required

Effect of Bioaugmentation on Biogas Yields and Kinetics in Anaerobic Digestion of Sewage Sludge

Bioaugmentation with a mixture of microorganisms (Bacteria and Archaea) was applied to improve the anaerobic digestion of sewage sludge. The study was performed in reactors operating at a temperature of 35 °C in semi-flow mode. Three runs with different doses of bioaugmenting mixture were conducted. Bioaugmentation of sewage sludge improved fermentation and allowed satisfactory biogas/methane yields and a biodegradation efficiency of more than 46%, despite the decrease in hydraulic retention time (HRT) from 20 d to 16.7 d. Moreover, in terms of biogas production, the rate constant k increased from 0.071 h−1 to 0.087 h−1 as doses of the bioaugmenting mixture were increased, as compared to values of 0.066 h−1 and 0.069 h−1 obtained with sewage sludge alone. Next-generation sequencing revealed that Cytophaga sp. predominated among Bacteria in digesters and that the hydrogenotrophic methanogen Methanoculleus sp. was the most abundant genus among Archaea

Modeling of Wastewater Treatment Processes in Membrane Bioreactors Compared to Conventional Activated Sludge Systems

Membrane techniques constitute an interesting alternative to conventional activated sludge systems (CAS). In membrane bioreactors (MBR), the biomass separated on membranes is retained independently of sludge sedimentation properties. As a consequence, a high biomass concentration as well as low food to microorganisms ratio can be obtained. Moreover, the development of a characteristic activated sludge population is stimulated by the specific conditions prevailing in MBRs. In the study, the operation and treatment efficiency of the MBR and CAS processes were examined and compared. Simulation was performed with the use of GPS-X software. The effluent quality obtained for the MBR system was either better or comparable to that of CAS. The most significant difference concerned the elimination of total suspended solids, which amounted to 99.8% in the MBR. Regarding nutrients, a low concentration of total phosphorus in the effluent from CAS and MBR was obtained (0.67 gP m−3 and 0.50 gP m−3, respectively). Greater differences were achieved in the case of total nitrogen. Although almost complete nitrification took place in both systems, a lower concentration of nitrate in the effluent from MBR in comparison to CAS, i.e., 11.2 gN m−3 and 14.1 gN m−3, respectively, allowed us to obtain a higher removal of total nitrogen (80.8% and 76.1%, respectively)

An Application of Orifice Hydrodynamic Cavitation Reactor for Tertiary Treatment of Wastewater Treatment Plant Effluents

In this paper, a multi-orifice hydrodynamic cavitator (HC) has been applied as an effective device for water reclamation. Municipal wastewater after mechanical and biological treatment has been applied as a medium. The effectiveness of using this device has been evaluated on the basis on the microbiological indicators. Moreover, optimization of operating parameters was evaluated. Two experiments with different inlet pressure of 0.4 and 0.6 MPa were performed. The samples for analyses were taken at the following time intervals: 0, 15, 30, 60 and 90 min. The application of HC reactor provided the effective destruction of microorganisms, thus allowing for subsequent use of reclaimed water. With regard to Escherichia coli and Coliform bacteria destruction, the longest time of 90 min and higher pressure of 0.6 MPa might be considered as the most advantageous conditions to perform cavitation. In both cases, the microbes were deactivated in over 50%. In the case of Enterococci, Pseudomonas aeruginosa and colony count, more beneficial results were found at lower pressure of 0.4 MPa and 90 min. Therein, the high level of microorganisms destruction was achieved varied between 81 and 92%. The applied HC allowed for selecting optimal operating parameters and process control through the application of gauge system

Effect of bioaugmentation on digestate metal concentrations in anaerobic digestion of sewage sludge.

This study examined the influence of bioaugmentation on metal concentrations (aluminum, cadmium, chromium, cobalt, copper, iron, lead, manganese, molybdenum, nickel and zinc) in anaerobically digested sewage sludge. To improve the digestion efficiency, bioaugmentation with a mixture of wild-living Archaea and Bacteria (MAB) from Yellowstone National Park, USA, was used. The total concentration of all metals was higher in the digestate than in the feedstock. During anaerobic digestion, the percent increase in the concentration of most of metals was slightly higher in the bioaugmented runs than in the un-augmented runs, but these differences were not statistically significant. However, the percent increase in cadmium and cobalt concentration was significantly higher in the bioaugmented runs than in the un-augmented runs. At MAB doses of 9 and 13% v/v, cadmium concentration in the digestate was 211 and 308% higher than in the feedstock, respectively, and cobalt concentration was 138 and 165%, respectively. Bioaugmentation increased over 4 times the percentage of Pseudomonas sp. in the biomass that are able to efficiently accumulate metals by both extracellular adsorption and intracellular uptake. Biogas production was not affected by the increased metal concentrations. In conclusion, bioaugmentation increased the concentration of metals in dry sludge, which means that it could potentially have negative effects on the environment

Technological and Energetic Aspects of Multi-Component Co-Digestion of the Beverage Industry Wastes and Municipal Sewage Sludge

In the present study, the co-digestion effectiveness of the selected beverage wastes and municipal sewage sludge in two- and three-component mixtures was evaluated. Orange peels and orange pulp, as well as brewery spent grain were applied as co-substrates to sewage sludge at the following doses: 1.5 and 3.0 g of orange peels, 2.5 and 5 g of orange pulp, and 1.5 g brewery spent grain. Mono-digestion of sewage sludge was used as a control. The experiments were performed under mesophilic conditions in batch reactors. As compared to the control, only in the presence of the highest dose of pulp, brewery spent grain and sewage sludge was the increased methane production of 395 mL CH4 g−1 VS accompanying an additional energy profit of 82% observed. Moreover, in this case, the enhanced volatile solids removal and lower accumulation of p-cymene were found. These results were despite the increased limonene and phenol content in the feedstock, confirming a synergistic effect at the highest dose of pulp, brewery spent grain and sewage sludge

Technological and Energetic Aspects of Multi-Component Co-Digestion of the Beverage Industry Wastes and Municipal Sewage Sludge

In the present study, the co-digestion effectiveness of the selected beverage wastes and municipal sewage sludge in two- and three-component mixtures was evaluated. Orange peels and orange pulp, as well as brewery spent grain were applied as co-substrates to sewage sludge at the following doses: 1.5 and 3.0 g of orange peels, 2.5 and 5 g of orange pulp, and 1.5 g brewery spent grain. Mono-digestion of sewage sludge was used as a control. The experiments were performed under mesophilic conditions in batch reactors. As compared to the control, only in the presence of the highest dose of pulp, brewery spent grain and sewage sludge was the increased methane production of 395 mL CH4 g−1 VS accompanying an additional energy profit of 82% observed. Moreover, in this case, the enhanced volatile solids removal and lower accumulation of p-cymene were found. These results were despite the increased limonene and phenol content in the feedstock, confirming a synergistic effect at the highest dose of pulp, brewery spent grain and sewage sludge

Mature Landfill Leachate as a Medium for Hydrodynamic Cavitation of Brewery Spent Grain

In this study, we evaluate the usefulness of mature landfill leachate (MLL) as a carrier allowing hydrodynamic cavitation (HD) of brewery spent grain (BSG). The HD experiments were conducted using an orifice plate with a conical concentric hole of 3/10 mm (inlet/outlet diameter) as a constriction in the cavitation device. The initial pressure was 7 bar and the number of recirculation passes through the cavitation zone reached 30. The results showed that complex organic matter was degraded and solubilized when cavitating the MLL and BSG mixture. The biochemical oxygen demand (BOD5) increased by 45% and the BOD5/total chemical oxygen demand (COD) ratio increased by 69%, whereas the COD, total solids, and nutrient concentration dropped noticeably. However, Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) revealed the generation of possibly toxic HD byproducts such as aromatic compounds. This seems to indicate that MLL could not be regarded as a suitable carrier for BSG cavitation

The Effect of Bioaugmentation with Archaea on the Oxygen Uptake Rate in a Sequencing Batch Reactor

The aim of this study was to evaluate the effect of bioaugmentation with Archaea domain organisms on the activated sludge (AS) expressed by the oxygen uptake rate (OUR) in a laboratory sequencing batch reactor (SBR). The influence of depletion of the external substrate in bioaugmented (SBR-A) and non-bioaugmented (SBR-B) activated sludge during aerobic stabilization was investigated. The experiment was divided into two steps. First, the OUR was measured in the standard conditions of biological treatment. Second, AS was only aerated in the absence of the substrate. It was observed that bioaugmentation with Archaea had an increasing effect on the endogenous and exogenous OUR of the sludge in both phases. In the first phase, the average endogenous OUR was 28.70 ± 2.75 and 21.63 ± 0.9 mgO2·dm−3·h−1 in the SBR-A and SBR-B, respectively. Regarding the exogenous OUR, the average values were 95.55 ± 11.33 and 57.15 ± 24.56 mgO2·dm−3·h−1 for the SBR-A and SBR-B, respectively. Archaea enhancing its biological activity, expressed as the OUR, exert a stabilizing effect on this parameter of AS and ensure its lower sensitivity to changes in the process conditions, substrate supply disruption and prolonged aeration

Thermophilic Co-Digestion of Sewage Sludge and Brewery Spent Grain

This study examined the effectiveness of thermophilic co-digestion of sewage sludge and milled/non-milled brewery spent grain. The experiments were performed in batch-mode to evaluate both the biogas potential and the biogas production rate. Five runs were carried out, one of them concerned the anaerobic digestion of sewage sludge (as control), whereas the others referred to the co-digestion of sewage sludge with addition of milled and nonmilled brewery spent grain at doses of 5 and 10 g. The runs were conducted under thermophilic conditions (temperature 55±1°C) and lasted for 21 days. The effectiveness of the process was assessed on the basis of the volatile solids removal, biogas potential and the rate of biogas production. The physiochemical composition of reactor feed and digestate were characterized. The addition of the brewery spent grain resulted in increase of the biogas potential, but a decrease in the volatile solids removal. In the case of biogas production rate, the highest value was recorded in the run with the addition of 10 g of milled and non-milled brewery spent grain (0.69 Ndm3dm-3d-1). There was no observed influence of milling on the thermophilic co-digestion effectiveness since the parameters specified revealed comparable values