Upflow Anaerobic Sludge Blanket Process Research Articles

Effects of organic loading and oil-grease for the treatment of edible oil effluent in a pilot-scale upflow anaerobic sludge blanket process

In this study, Karadeniz Birlik Dogan Erdil vegetable oil factory, Elazig City, Turkey, was selected as representative of this sector. During the first part of the test programme, the quality of raw effluents was investigated. The removals of COD and oil-grease were above 85% at organic loadings between 1.62 and 7.83 kg COD m-3 d-1 at hydraulic retention times of 2.0 and 2.5 days. The conversion rates of the removed COD into methane gas were between 0.24 and 0.361 g CH4 (g COD)-1.

Biological sulfate reduction using molasses as a carbon source.

The feasibility of using a laboratory-scale upflow anaerobic sludge blanket process for sulfate reduction with molasses as a carbon source was demonstrated. Competition between methane-producing bacteria (MPB) and sulfate-reducing bacteria (SRB) was influenced by the chemical oxygen demand-to-sulfur (COD:S) ratio in the feed. Sulfate removal greater than 80% could be achieved at COD:S greater than 10 when MPB predominated. Activity of MPB and SRB was inhibited at a dissolved sulfide concentration of approximately 200 mg/L. Competition between MPB and SRB was intense as the COD:S was reduced from 5 to 2. Further reduction in the COD:S to 0.7 led to the formation of sulfidogenic granules. The COD removal decreased to approximately 30% at a COD:S less than 2 because of accumulation of sulfurous precipitates and the nonbiodegradable portion of molasses in the sludge. Reduced gas production rates further imposed limitations on diffusion of the organic substrate into granules. Sulfidogenic process operation yielded sulfate removal as great as 70% at a COD:S of approximately 3.5.

Sensitivity of anaerobic sludge biogranule to sulfur compounds

The effects of sulfide, sulfite and sulfate on the methanogenesis in an upflow anaerobic sludge blanket process indicated that their relative toxicity towards degradation of total volatile fatty acid varied as SO42−-S>SO32−-S>S2−. The anaerobic biogranules' activity decreased by 50% when each gram of biomass came into contact with 32, 24 and 16 mg of S2−, SO32−-S and SO42−-S, respectively.

Biosorption of long-chain fatty acids in UASB treatment process

Biosorption of long-chain fatty acids (LCFA) in the upflow anaerobic sludge blanket (UASB) treatment process was investigated using batch tests and continuous reactor runs. Batch experiments were conducted, for characterization of the biosorption, with two active and one inactivated (autoclaved) sludge granules as sorbents and with a single (oleic acid) or a mixture of LCFA (LCFA m; 50% oleic, 35% palmitic and 15% stearic acid) as sorbates. The LCFA m showed a faster adsorption onto the granules than oleic acid. With the active sludge granules, adsorption was followed by desorption. Methane production increased significantly, either simultaneously (at lower LCFA concentrations) or succeedingly (at higher concentrations) with desorption. The desorption was mediated by biological activity, since it did not prevail with inactivated granules or with active granules inhibited at higher LCFA m concentrations. The inactivated granules had a slightly higher initial biosorption capacity. Increased LCFA concentrations resulted in more LCFA adsorbed and greater inhibition of their biodegradation. A hypothesis is proposed to explicate the relationship between biosorption, desorption and biodegradation of LCFA by sludge granules: adsorption is a prerequisite for biodegradation while desorption is a consequence of biodegradation. Isothermal studies with oleate showed that the apparent biosorption could be described by the physical multilayer adsorption theory and the sorption isotherm derived was consistent with the Freundlich model. The quantitative relation between LCFA biosorption and granular sludge flotation was investigated in a UASB reactor fed with LCFA m. Sludge flotation depended on the LCFA m loading rate rather than on their concentration. The higher the loading implemented, the more flotation occurred and the shorter time required for complete flotation of the sludge bed. Flotation started when the LCFA m loading rate exceeded 0.09 g COD/g VSS·d, while complete flotation occurred at the loading rates exceeding 0.2 g COD/g VSS·d. These results suggest that sludge bed wash-out is likely to be encountered before inhibition of methanogenesis during the treatment of LCFA-containing wastewaters by the UASB process.

Pilot study of UASB process treating PTA manufacturing wastewater

A pilot-scale upflow anaerobic sludge blanket (UASB) reactor was employed to treat the wastewater of a purified-terephthalic-acid (PTA) manufacturing factory. The performance of UASB reactor in terms of COD removal was achieved 62% at the volumetric loading rate of 2.93 kg COD / m3/day. One of the major constituents, p-toluic acid in PTA wastewater was the refractory component due to the methyl substituent on the aromatic ring, which restricted the biodegradation performance. Moreover, from our study, it was surprising that high concentration of acetic acid would retard the degradation of aromatics in the sludge bed. A control strategy of acetic acid level in the sludge bed was suggested during the start-up period. Comparison of the anaerobic biodegradability of aromatic substituents in PTA wastewater was concluded as the following sequence: –COOH > –CHO ≥ –CH3 in terms of the derivative functional groups based on the benzoic acid. Observation of bacterial population of the sludge granules showed high diversity of syntrophic structure on the biogranular surface as well as acetoclastic methanogens.

Effect of heavy metals on the upflow anaerobic sludge blanket process

This study examined the effects of ionic chromium, cadmium, lead, copper, zinc, and nickel on methane production and volatile fatty acid (VFA) production in an upflow anaerobic sludge blanket (UASB) reactor using serum bottle assays. The granular seed sludges were acclimated with glucose by continuous feeding. According to experimental results, effects of the metals relied on the sludge zones, VFA types and metal types. The metal concentrations that caused 50% inhibition of methane production and total VFA production ranged from 210–2640 mg/L and 350∼>>5000 mg/L, respectively. The metals’ relative toxicity to total VFA degradation was in the order of Cu>>Cr>Cd≫Zn>Ni>Pb and Cu>>Cdr=Cr>>Ni>Zn>Pb for bed and blanket sludges, respectively. Our results also confirmed copper and lead to be the most toxic and least toxic metals tested, respectively. In UASB biogranules, the organisms responsible for methane production were less resistant to metal toxicity than those responsible for VFA production.

Effects of sulfide, sulfite and sulfate on acidogenesis in upflow anaerobic sludge blanket process

The effects of sulfide, sulfite and sulfate on the production of volatile fatty acid (VFA) in an upflow anaerobic sludge blanket process were investigated by using serum bottle assays. The seed sludges were acclimated with glucose by continuous feeding. It is known that the activity of acidogenic granular sludge is affected by the sulfur compounds. Inhibitions at high concentrations while low concentrations stimulated VFA production were observed in the present study. The effects were observed to be VFA dependent and the relative toxicity of sulfur compounds to total VFA production was found to vary as SO3 2‐‐S>SO4 2‐‐S>S2‐ for bed as well as blanket zone sludges. Different degrees of toxicity were, however, observed for individual VFA and sludges. At small concentrations these compounds stimulated the production of individual VFA. This stimulation was observed to depend on the types of sulfur compound, zones of sludge as well as types of VFA.

Pilot study of UASB process treating PTA manufacturing wastewater

A pilot-scale upflow anaerobic sludge blanket (UASB) reactor was employed to treat the wastewater of a purified-terephthalic-acid (PTA) manufacturing factory. The performance of UASB reactor in terms of COD removal was achieved 62% at the volumetric loading rate of 2.93 kg COD / m3/day. One of the major constituents, p-toluic acid in PTA wastewater was the refractory component due to the methyl substituent on the aromatic ring, which restricted the biodegradation performance. Moreover, from our study, it was surprising that high concentration of acetic acid would retard the degradation of aromatics in the sludge bed. A control strategy of acetic acid level in the sludge bed was suggested during the start-up period. Comparison of the anaerobic biodegradability of aromatic substituents in PTA wastewater was concluded as the following sequence: -COOH > -CHO ≥ -CH3 in terms of the derivative functional groups based on the benzoic acid. Observation of bacterial population of the sludge granules showed high diversity of syntrophic structure on the biogranular surface as well as acetoclastic methanogens.

UASB Treatment of Wastewater with Concentrated Mixed VFA

The upflow anaerobic-sludge blanket (UASB) process consistently removed 97–99% of chemical oxygen demand (COD) from wastewater containing concentrated mixed volatile fatty acids (VFA) at 37°C at loading rates of up to 24 g-COD/(Lsd) corresponding to a food/microorganism ratio of 0.78 g-COD/[g–volatile suspended solids (VSS)sd]. It suggested that, with preacidification, the UASB process can be effective for a wide variety of wastewaters. The COD removal efficiency deteriorated at higher loading rates; there was no butyrate in the effluent, suggesting that butyrate degradation was not a rate-limiting step. Of the COD removed, 92.6% was converted to methane; the rest was converted to granular biomass with an average yield of 0.054 g-VSS/g-COD. The granules had a size of 1–2 mm and settled satisfactorily. Each gram of granule in the reactor was capable of converting a daily maximum of 0.86 g of COD into methane. The granules had a fluffy surface mostly composed of interwound filamentous \IMethanothrix\N-like bacteria. Syntrophic associations between \IMethanothrix-, Methanospirillum hungatei-, \N and \ISyntrophobacter\N-like bacteria were prevalent in the granule interior. The syntrophic relation between these species was elucidated by thermodynamics.

Effects of Wastewater Composition on Stability of UASB

Three types of wastewater based on acetate, sucrose, and ice cream were used to investigate the long‐term effect of wastewater composition on the stability of the upflow anaerobic sludge blanket (UASB) process using laboratory‐scale reactors. Experimental results revealed that variations in the carbon source in the wastewater caused gradual changes in both the physical structures and the bacterial distribution of the seeding granular sludge, which resulted in disintegration or floatation of the granular sludge under certain conditions. The rate of such changes was found to be relatively slow, and depended on the sludge‐loading rate. A semiquantitative mathematical model on the ecological characteristics of the granular sludge was developed and was able to explain the experimental results. The study suggests that the failure of the UASB process under certain circumstance was primarily due to the limitation in the ecological structure of the granular sludge.

Anaerobic Treatment of Sewage Sludge Treated by Catalytic Wet Oxidation Process in Upflow Anaerobic Sludge Blanket Reactors

To increase the efficiency of methane recovery in anaerobic treatment, sewage sludge was treated by catalytic wet oxidation process(CWOP).The CWOP is designed to treat sewage sludge with the aid of a newly developed catalyst. It is a treatment process, by which concentrated COD components and suspended solids in various kinds of sludge can be simultaneously oxidized and treated with great efficiency in a single step without dilution. After CWOP, this supernatant was treated by upflow anaerobic sludge blanket(UASB) for recovery of methane. This experiment was to evaluate the acclimation of UASB process to the supernatant of sewage sludge treated by CWOP. For the granule growth and accumulation, supernatant was introduced stepwise (25%, 33%, 50%, 100%). The supernatant was 7,200 mg-COD/L which contained 53% carbonic acids. The reactor was operated at a volumetric loading rate from 1.8 (kg·COD/m3·day) to 14.4 (kg·COD/m3·day) and overall HRT of less than 24 hrs throughout the experiment. In the conventional anaerobic biochemical process of methane gas recovery was limited to 50% of COD recovery. As a result of this study, the COD recovery to about 93% was obtained by the coebination of CWOP and UASB process. The following conditions were enough for pretreatment: temperature, 270°C; pressure, 86kg/m2; stoichiometric air ratio, 1.1; reaction time, 24 min. These results indicate that the CWOP-UASB process may be attractive as an alternative sewage sludge treatment.

Application of the Biobed® Upflow Fluidized Bed Process for Anaerobic Waste Water Treatment

Over the past ten years Gist-brocades has been engaged in anaerobic waste water treatment. An in-depth research program concluded in the construction and operation of three full-scale plants for the treatment of yeast processing and pharmaceutical waste waters. Using the operational experience of the fluidized bed biomass-on-carrier systems and incorporating the strong assets of the Upflow Anaerobic Sludge Blanket (UASB) system features a new process was developed, the so-called Upflow Fluidized Bed (UFB) BIOBED® process, which operation appeared to be very successful over a > 3 year period at full scale. The UFB BIOBED® system combines both characteristics of the UASB and FB processes. Biomass is present in a granular form but conditions with respect to upflow velocities for water and gas approach those of the original Fluidized Bed - biomass on carrier - (FB) system.

A Modified UASB Process Treating Winery Wastewater

During the last two years,twenty-seven bioreactors of upflow anaerobic sludge blanket(UASB) process were constructed and operated well to treat 3,300 m3/day of winery wastewater in six winery plants in Taiwan. Each UASB reactor was installed with an internal filter and a side-armed sludge settler to separate gas-liquid-solid effectively in 127 m3 of reactor volume.These six plants established good performance of UASB process with different organic loadings depending on different characteristics of the winery wastewater. Start-up performance of the modified UASB process in four winery plants was investigated.Bioactivity of anaerobic sludge in each UASB was evaluated by means of Biochemical Methane Potential (BMP)test. Biokinetics of Monod and Haldane models were employed to interpret the different sludge characteristics in terms of gas production rate. Scanning electronic microscopy also showed different morphology of sludge granules in three UASB systems.

Treatment of Brewery Effluent by UASB Process

A five‐month pilot study was conducted to examine the effectiveness of the upflow anaerobic sludge blanket (UASB) process for the treatment of effluent from a brewery in rural China. Results indicate that the process operated at 26° C could reduce over 89% of chemical oxygen demand (COD) and 92% of five‐day biochemical oxygen demand (BOD5) from the brewery effluent, with a hydraulic retention time (HRT) of 13.3 hr and a COD loading rate of 4.9 kg COD/m3/day. The brewery effluent in this study on average contained 2,692 ppm COD and 1,407 ppm BOD5. The treated effluent on the other hand contained 295 ppm COD and 122 ppm BOD5; both of which could be further reduced should the suspended solids be more effectively removed. Overall, this process was operated satisfactorily and smoothly, as reflected by the constant effluent pH and gas production rate, as well as the consistently high degrees of reduction of COD and BOD5. Parameters such as sludge density, distribution of volatile suspended solids (VSS) and soluble COD in sludge bed, gas production rate, and nutrient levels are discussed.

Thermophilic anaerobic digestion of sugars in upflow anaerobic sludge blanket reactors

In recent years numerous designs have been developed for the high-rate anaerobic treatment of wastewater.'-6 All these processes have their advantages and drawbacks, which have been discussed repeatedly (see, for example, ref. 7). Of these processes, the upflow anaerobic sludge blanket (UASB) process is currently the most widely applied, at least in Western Europe. It is successfully applied in the treatment of wastewaters from maize and potato starch industries and sugar beet and potato processing industries.' Perhaps the main advantage of the UASB process is that no specific support material is required. However, this main advantage may sometimes be a serious drawback: the absence of support material necessitates the availability of a sludge with very good settling properties. Whenever such a sludge is obtained, or can be maintained, successful operation of the UASB process is readily achieved. Under certain circumstances the settleability of the sludge in UASB reactors is greatly improved because bacterial growth is in the form of spherical flocs with a quite consistent structure, normally referred to as granular sludge.6 Although already considerable research has been performed on factors considered to be important in the phenomenon of gran~lation,~- the knowledge on this matter is still relatively poor. Thermophilic anaerobic digestion may become an attractive alternative for mesophilic digestion because of the higher growth rates of the bacteria involved and, consequently, the higher maximum activities per unit of biomass. As the specific growth rates of the methane-forming bacteria of the genus Methanothrix, which are believed to be the predominant acetoclastic methanogens in methane digestion processes with a high biomass retention time,L2313 is ca. 2.5 times as high at 55°C as at 30°C,'2.'3 also a 2.5 times higher methanogenic acitivity per unit of biomass may be expected. Also, in thermophilic sewage sludge digestion a Methanosarcina was found to be the predominant acetoclastic methanogen, which even has a higher specific growth rate than the thermophilic Methanothrix. l 4 The successful operation of high-rate thermophilic systems requires a high activity per unit of volume, and therefore a high biomass retention is a prerequisite. In view of the successful use under mesophilic conditions, we investigated the thermophilic UASB process for this purpose. Glucose was chosen as the substrate because granulation is reported to occur in UASB reactors when it is the substrate for a acid-formation process.

Design Operation and Economy of Anaerobic Treatment

This paper aims to contribute to the assesment of a (more) optimal design and operation of a high rate anaerobic waste water treatment process. The discussion will be made on basis of available information of modern anaerobic waste water treatment processes, such as the Anaerobic Filter Process and the Upflow Anaerobic Sludge Blanket process and of recently introduced Attached Film processes.