Improvement of anaerobic digestion of sludge

2004 ◽  
Vol 49 (10) ◽  
pp. 89-96 ◽  
Author(s):  
M. Dohányos ◽  
J. Zábranská ◽  
J. Kutil ◽  
P. Jeníček
Keyword(s):  
Particulate Matter ◽  
Anaerobic Digestion ◽  
Energy Balance ◽  
Activated Sludge ◽  
High Resistance ◽  
Biogas Production ◽  
Treatment Plant ◽  
Process Conditions ◽  
Digested Sludge ◽  
Acceptable Method

Anaerobic digestion improvement can be accomplished by different methods. Besides optimization of the process conditions, pretreatment of input sludge and increase of process temperature is frequently used. The thermophilic process brings a higher solids reduction and biogas production, a high resistance to foaming, no problems with odour, better pathogens destruction and an improvement of the energy balance of the whole treatment plant. Disintegration of excess activated sludge in a lysate centrifuge was proved to cause increase of biogas production in full-scale conditions. The rapid thermal conditioning of digested sludge is an acceptable method of particulate matter disintegration and solubilization.

Mesophilic and Thermophilic Digestion of Thickened Waste Activated Sludge: A Comparative Study

2010 ◽  
Vol 113-116 ◽  
pp. 450-458 ◽  
Author(s):  
Yong Zhi Chi ◽  
Yu You Li ◽  
Min Ji ◽  
Hong Qiang ◽  
Heng Wei Deng ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Treatment Plant ◽  
Methane Content ◽  
Waste Activated Sludge ◽  
Digested Sludge ◽  
Anaerobic Digestion Process ◽  
Digestion Process ◽  
Significant Difference

This paper presents an experimental study over 204 days on anaerobic degradation of thickened waste activated sludge (TWAS) from a municipal wastewater treatment plant (WWTP). The experiments were conducted under thermophilic (55°C) and mesophilic (35°C) condition, respectively, by using the semi-continuous flow completely mixed reactors. The influent total solids (TS), hydraulic retention time (HRT) and chemical oxygen demand (COD) loading levels were around 4%, 30 days and 1.67 kg-CODCr•m-3•d-1 , respectively. During the opration period, the thermophilic anaerobic digestion process (TADP) and the mesophilic anaerobic digestion process (MADP) were stable and well-functioned without ammonia inhibition. Particulate organic matters reduction of TADP was superior to that of MADP. This result implies that TADP has higher sludge reduction efficiency than MADP. According to the simulated chemical formula of TWAS, C5.85H9.75O3.96N, and the stoichiometric equation, the methane content and the ammonia yield in the anaerobic process could be calculated, which were consistent with the experimental results. The methane yield of TADP was a little higher than that of MADP. The statistical mean values of methane content for TADP and MADP were 60.97% and 62.38%, respectively.According to paired t-test, there was a significant difference in methane content between TADP and MADP(α=0.01, n=62). Compared with the mesophilic digested sludge, the dewaterability of thermophilic digested sludge was lower.

A Performance Study of Aerobic Sludge Digestion

1973 ◽  
Vol 8 (1) ◽  
pp. 26-35
Author(s):  
K.S. Hogg ◽  
J. Ganczarczyk
Keyword(s):  
Activated Sludge ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Climatic Conditions ◽  
Anaerobic Sludge ◽  
Process Conditions ◽  
Performance Study ◽  
Digested Sludge ◽  
Sludge Digestion ◽  
Aerobic Sludge

Abstract The aerobic sludge digestion system at the sewage treatment plant at Dunnville, Ontario was designed as a one-stage aeration process (by means of the Inka system) of moderately concentrated excess activated sludge (less than 1 percent of TS), followed by continuous sludge thickening and sludge drying lagoons for the final dewatering of the digestion product. An evaluation of this system was conducted in the summer of 1972. It included the study of sludge and supernatant characteristics, phosphorus balance and an economical comparison of the costs associated with this type of aerobic digestion and anaerobic sludge digestion for similar size (about 1.7 IMGD) activated sludge process plants. Results of the investigations disclosed that the aerobic digester with sludge loading of about 0.03 lb VS/cu ft/day and an average hydraulic detention time of only 9.2 days, operated satisfactorily at the summer climatic conditions of Southern Ontario. This process, however, could not be judged on the basis of volatile solids reduction, which proved to be only equal to 6 percent. This phenomenon was probably due to the solubility in water of a part of the mineral constituents of the sludge under the process conditions. The change in the sludge specific oxygen uptake rates from 8.9 to 2.75 mg 02/gVSS/hr at 25°C, was a more reliable indicator of the digested sludge characteristics. Supernatant quality (average COD of 170 mg/l and SS of 110 mg/l) and the dewaterability of the digested sludge (average resistance to filtration equal to 0.86 x 1013 m/kg) provided additional information of the digester’s performance.

Aeration of anaerobically digested sewage sludge for COD and nitrogen removal: optimization at large-scale

2008 ◽  
Vol 57 (2) ◽  
pp. 257-264 ◽  
Author(s):  
V. Parravicini ◽  
K. Svardal ◽  
R. Hornek ◽  
H. Kroiss
Keyword(s):  
Wastewater Treatment ◽  
Anaerobic Digestion ◽  
Sewage Sludge ◽  
Nitrogen Removal ◽  
Wastewater Treatment Plant ◽  
Treatment Plant ◽  
Process Conditions ◽  
Nitrite Accumulation ◽  
Digested Sludge ◽  
Digested Sewage Sludge

The paper will report about the experiences at an Austrian large wastewater treatment plant of 720,000 population equivalents, where anaerobically digested sewage sludge is further stabilised under aerobic conditions. Enhanced stabilisation of the anaerobically digested sludge was required at the plant in order to get a permit for landfill disposal of the dewatered stabilized sludge. By implementing a post-aeration treatment (SRT ∼ 6d; 36 °C) after anaerobic digestion the organic content of the anaerobically well digested sludge can be decreased by 16%. Investigations on site showed that during digested sludge post-aeration anoxic phases for denitrification are needed to provide stable process conditions. In this way the pH value can be kept in a more favourable range for micro-organisms and concrete structures. Additionally, inhibition of the biological process due to nitrite accumulation can be avoided. By optimising the aeration/pause ratio ∼ 45% of total nitrogen in digested sludge can be removed. This significantly improves nitrogen removal efficiency at the wastewater treatment plant. NH4-removal occurs mainly through nitritation and denitritation with an efficiency of 98%. The costs/benefit analysis shows that post-aeration of digested sludge results in an increase of total annual costs for wastewater treatment of only 0.84%, corresponding to 0.19 Euro/pe/a. Result of molecular biological analyses (DGGE) indicate that all four ammonium-oxidizing bacteria species present in activated sludge can survive anaerobic digestion, but only two of them can adapt in the digested sludge post-aeration tanks. Additionally, in the post-aerated digested sludge a further ammonium-oxidizing bacteria species was identified.

scholarly journals Influence of chemically enhanced primary treatment on anaerobic digestion and dewaterability of waste sludge

2017 ◽  
Vol 76 (7) ◽  
pp. 1629-1639 ◽  
Author(s):  
G. Kooijman ◽  
M. K. De Kreuk ◽  
J. B. van Lier
Keyword(s):  
Anaerobic Digestion ◽  
Biogas Production ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Primary Treatment ◽  
Hydrolysis Rate ◽  
Biological Degradation ◽  
Digested Sludge ◽  
N Removal ◽  
Chemically Enhanced Primary Treatment

To lower energy consumption at a sewage treatment plant (STP), primary settling could be enhanced to direct more chemical oxygen demand (COD) to anaerobic digestion (AD) for increased biogas production and decreased aeration. Primary settling can be chemically enhanced by applying flocculation aids (FAs). FAs are refractory compounds that may affect all sludge treatment facilities. In this study the consequences are investigated of the application of FAs for chemically enhanced primary treatment (CEPT) on AD and subsequent dewatering of digested sludge in a conventional STP. It was found that FAs maintain their effect throughout all sludge processing facilities. With CEPT, more readily degradable solids were removed, resulting in a higher bio methane potential of the primary sludge. In AD, FAs lowered the viscosity; meanwhile an increased hydrolysis rate was observed. But FAs also partially irreversibly bound substrate in such way that it is not available for biological degradation anymore. In subsequent dewatering of digested sludge, a higher dry solids concentration was observed with CEPT. A computer simulation showed that in a conventional STP, CEPT would not be economically feasible. However, several benefits were discussed that can make CEPT an interesting option for future low COD/N-tolerant STPs with, for example, Anammox processes for N removal.

Disintegration of excess activated sludge – evaluation and experience of full-scale applications

2006 ◽  
Vol 53 (12) ◽  
pp. 229-236 ◽  
Author(s):  
J. Zábranská ◽  
M. Dohányos ◽  
P. Jeníček ◽  
J. Kutil
Keyword(s):  
Organic Matter ◽  
Anaerobic Digestion ◽  
Sewage Sludge ◽  
Activated Sludge ◽  
Biogas Production ◽  
Full Scale ◽  
Energy Yield ◽  
Operational Experience ◽  
Digested Sludge

Anaerobic digestion of sewage sludge can be improved by introducing a disintegration of excess activated sludge as a pretreatment process. The disintegration brings a deeper degradation of organic matter and less amount of output sludge for disposal, a higher production of biogas and consequently energy yield, in some cases suppression of digesters foaming and better dewaterability. The full-scale application of disintegration by a lysate-thickening centrifuge was monitored long term in three different WWTPs. The evaluation of contribution of disintegration to biogas production and digested sludge quality was assessed and operational experience is discussed. Increment of specific biogas production was evaluated in the range of 15–26%, organic matter in digested sludge significantly decreased to 48–49%. Results proved that the installation of a disintegrating centrifuge in WWTPs of different sizes and conditions would be useful and beneficial.

A modified anaerobic digestion process with chemical sludge pre-treatment and its modelling

2014 ◽  
Vol 69 (11) ◽  
pp. 2350-2356 ◽  
Author(s):  
N. M. Hai ◽  
S. Sakamoto ◽  
V. C. Le ◽  
H. S. Kim ◽  
R. Goel ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Biogas Production ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Municipal Wastewater Treatment ◽  
Simulation Accuracy ◽  
Volatile Solids ◽  
Pre Treatment

Activated Sludge Models (ASMs) assume an unbiodegradable organic particulate fraction in the activated sludge, which is derived from the decay of active microorganisms in the sludge and/or introduced from wastewater. In this study, a seasonal change of such activated sludge constituents in a municipal wastewater treatment plant was monitored for 1.5 years. The chemical oxygen demand ratio of the unbiodegradable particulates to the sludge showed a sinusoidal pattern ranging from 40 to 65% along with the change of water temperature in the plant that affected the decay rate. The biogas production in a laboratory-scale anaerobic digestion (AD) process was also affected by the unbiodegradable fraction in the activated sludge fed. Based on the results a chemical pre-treatment using H2O2 was conducted on the digestate to convert the unbiodegradable fraction to a biodegradable one. Once the pre-treated digestate was returned to the digester, the methane conversion increased up to 80% which was about 2.4 times as much as that of the conventional AD process, whilst 96% of volatile solids in the activated sludge was digested. From the experiment, the additional route of the organic conversion processes for the inert fraction at the pre-treatment stage was modelled on the ASM platform with reasonable simulation accuracy.

Simulation of the Impact of Higher Ammonia Recycle Loads Caused by Upgrading Anaerobic Sludge Digesters

2005 ◽  
Vol 40 (4) ◽  
pp. 491-499 ◽  
Author(s):  
Jeremy T. Kraemer ◽  
David M. Bagley
Keyword(s):  
Anaerobic Digestion ◽  
Biogas Production ◽  
Treatment Plant ◽  
Anaerobic Sludge ◽  
Content Increase ◽  
Limited Information ◽  
Dynamic Simulations ◽  
Treatment Train ◽  
Temperature Liquid ◽  
The Impact

Abstract Upgrading conventional single-stage mesophilic anaerobic digestion to an advanced digestion technology can increase sludge stability, reduce pathogen content, increase biogas production, and also increase ammonia concentrations recycled back to the liquid treatment train. Limited information is available to assess whether the higher ammonia recycle loads from an anaerobic sludge digestion upgrade would lead to higher discharge effluent ammonia concentrations. Biowin, a commercially available wastewater treatment plant simulation package, was used to predict the effects of anaerobic digestion upgrades on the liquid train performance, especially effluent ammonia concentrations. A factorial analysis indicated that the influent total Kjeldahl nitrogen (TKN) and influent alkalinity each had a 50-fold larger influence on the effluent NH3 concentration than either the ambient temperature, liquid train SRT or anaerobic digestion efficiency. Dynamic simulations indicated that the diurnal variation in effluent NH3 concentration was 9 times higher than the increase due to higher digester VSR. Higher recycle NH3 loads caused by upgrades to advanced digestion techniques can likely be adequately managed by scheduling dewatering to coincide with periods of low influent TKN load and ensuring sufficient alkalinity for nitrification.

scholarly journals Biochemical Methane Potential of Cork Boiling Wastewater at Different Inoculum to Substrate Ratios

2021 ◽  
Vol 11 (7) ◽  
pp. 3064
Author(s):  
Roberta Mota-Panizio ◽  
Manuel Jesús Hermoso-Orzáez ◽  
Luis Carmo-Calado ◽  
Gonçalo Lourinho ◽  
Paulo Sérgio Duque de Brito
Keyword(s):  
Anaerobic Digestion ◽  
Biogas Production ◽  
Treatment Plant ◽  
Organic Substrates ◽  
Biochemical Methane Potential ◽  
Volatile Solids ◽  
Working Volume ◽  
Methane Potential ◽  
Bmp Test ◽  
Cork Industry

The present study evaluates the digestion of cork boiling wastewater (CBW) through a biochemical methane potential (BMP) test. BMP assays were carried out with a working volume of 600 mL at a constant mesophilic temperature (35 °C). The experiment bottles contained CBW and inoculum (digested sludge from a wastewater treatment plant (WWTP)), with a ratio of inoculum/substrate (Ino/CBW) of 1:1 and 2:1 on the basis of volatile solids (VSs); the codigestion with food waste (FW) had a ratio of 2/0.7:0.3 (Ino/CBW:FW) and the codigestion with cow manure (CM) had a ratio of 2/0.5:0.5 (Ino/CBW:CM). Biogas and methane production was proportional to the inoculum substrate ratio (ISR) used. BMP tests have proved to be valuable for inferring the adequacy of anaerobic digestion to treat wastewater from the cork industry. The results indicate that the biomethane potential of CBWs for Ino/CBW ratios 1:1 and 2:1 is very low compared to other organic substrates. For the codigestion tests, the test with the Ino/CBW:CM ratio of 2/0.7:0.3 showed better biomethane yields, being in the expected values. This demonstrated that it is possible to perform the anaerobic digestion (AD) of CBW using a cosubstrate to increase biogas production and biomethane and to improve the quality of the final digestate.

scholarly journals CONSIDERATIONS ON RECYCLING POSSIBILITIES OF AGRO-INDUSTRIAL WASTES BY ANAEROBIC DIGESTION TREATMENT

1970 ◽  
Vol 63 ◽  
Author(s):  
Maria V. Morar
Keyword(s):  
Anaerobic Digestion ◽  
Biogas Production ◽  
Bacterial Flora ◽  
Waste Water Treatment ◽  
Treatment Plant ◽  
Water Treatment Plant ◽  
Anaerobic Treatment ◽  
Industrial Wastes ◽  
Waste Water Treatment Plant ◽  
Industrial Processing

In our country, the developments of the measures for the prevention of the environmental pollution are aligning to the UE Directives. The costs for the treatment of the water wastes are continuously increasing, following to the also increasing of the investments costs. Therefore it is necessary to accord attention for the alternatives of cleaning, treating, respective recycling of the agro-industrial wastes and their reintroduction in the natural circuit. At the processing of the food results wastes with high organic charge. The effluents form the processing of dairy products, sugar, starch, beer yeasts as well as breweries or distilleries are getting fast into acids fermentation, finally resulting organic acids. Such process water wastes can be released in the canalization by dilution or by a suitable treating. As an example, for the distillery wastes (distillery slops) with a high dry matter contents (4-20%), the waste water treatment plant shall be designed properly (with mechanical separation step and biological treatment) to ensure the capacity of purifying according to the high flow and increased concentration, due to the high CBOD5 concentration. The treatment of such water wastes can be realized with aerobic processes, which suppose a high energetic consumption. While in the aerobic purifying processes 50 % of the CBOD5 is involved in the forming of biomass and slurry in excess, in the anaerobic treatment processes (anaerobic or methane digestion) a high part of the substrate (until 70 %) is metabolized through the metabolic transformation of bacterial flora, with production of biogas. Therefore, the concentrated water wastes, with potential for the energy production could offer a possibility of energy replacement in the own processing units. The paper presents a review of the anaerobic digestion for different wastes from the agro-industrial processing and their potential for the biogas production. There are presented possibilities of mixture, respectively of co-digestion of different wastes the agro-industrial processing with other wastes from the agriculture (from cereals processing, biomass, manure etc). Simultaneously biogas plants from the praxis with functioning characteristics are presented.

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