The characteristics of granules from upflow anaerobic sludge blanket reactors

Granules from an industrial UASB reactor were maintained in bench scale (201.) UASB reactors and fed with a synthetic medium based on volatile fatty acids.

After 60 days of reactor operation, three distinct granule types were found to have evolved within the reactors. These types were defined by their colour: black, grey and white. These granules also differed in structure (texture) and elemental composition. The proportion of black, grey and white granules in the bed changed when the organic loading rate was changed. At the low loading rate, a large number of “hollow” granules appeared which were less dense than the liquid and were washed out at the top of the reactor.     

Modeling of the upflow anaerobic sludge bed-filter system: a case with hysteresis

A hybrid upflow sludge bed-filter (UBF) anaerobic reactor was successfully used for treatment of synthetic soluble 1% sugar waste. An hysteresis phenomenon was observed and discussed with respect to changes in acidogenic/acetoclastic specific activities ratio. The Haldane equation was adapted for predicting performance inhibition by undissociated acids as a function of substrate-COD and pH. The Monod and adapted Haldane models were solved simultaneously with substrate mass balance for a UBF reactor. The soluble COD removal efficiency and methane productivity were predicted as a function of the dilution rate. Critical values of solid and hydraulic residence times were also estimated and discussed in detail.     

Effect of settling on performance of the upflow anaerobic sludge bed reactors

The effects of settler volume on the start-up and steady-state performance of 41. laboratory upflow sludge bed reactors treating bean blanching waste of 10,000 mg COD l⁻¹ were determined. The rate of start-up, as well as the maximum loading rate, increased with increased settler volume and performance. A loading rate of 30 kg COD m⁻³ day⁻¹ (based on reactor volume alone) and a COD removal of 95% was obtained with a 21. settling flask and a 4 to 1 recirculation rate. Without a settler, the maximum loading rate was 10 kg COD m⁻³ day⁻¹. The sludge was flocculent rather than granular. Sludge profiles and characteristics in the reactors and settlers were determined.     

Metals in sugarcane molasses wastewater subjected to thermophilic anaerobic digestion

ABSTRACT

This study evaluated the occurrence and removal of eleven trace elements, B, Co, Cu, Fe, Mn, Mo, Ni, Se, V, W and Zn, from sugarcane molasses wastewater through a thermophilic anaerobic structured-bed reactor (AnSTBR). Concentration ranges in molasses were, in μg. L^?1: 19–277; 6–18; 37–449; 155–2160; 26–392; 3–15; 6–41; 12–46; 6–31; and 25–1648; for B, Co, Cu, Fe, Mn, Mo, Ni, Se, V, and Zn, respectively. Tungsten was not identified in the molasses. The average metal/nutrient removal efficiency was 62 ± 12, 58 ± 22, 55 ± 28, and 49 ± 12% for selenium, manganese, molybdenum, and iron, respectively. It is possible that the overall anaerobic digestion functioning is not affected up to these reported metal values. Environmental impacts from releasing effluent streams into soils and groundwater need to be investigated.     

高盐分餐厨垃圾湿式单级厌氧消化的试验研究

对高盐分餐厨垃圾湿式厌氧发酵进行了研究,试验结果表明:发酵液盐分浓度不断累积,由最初的0.084%增长至0.69%,并且还在继续增加;进料有机负荷控制在3 kgVS/(m3·d)时,反应器运行良好,发酵液COD稳定在2 620 mg/L左右,VFA浓度保持在880 mg/L以下,产气量81 L/d,甲烷含量60%左右.     

厌氧反应器中沼气泄漏扩散模拟研究

基于FDS建立沼气泄漏扩散模型,分别模拟管道接头破损、导凝管阀门破损和沼气突破水封,探究厌氧反应器中沼气泄漏扩散的基本规律.结果表明:当管道接头破损、导凝管阀门破损时,沼气泄漏后的危险范围为下风向处距离泄漏口约5m;当沼气突破水封时,沼气泄漏后的危险范围为下风向处距离泄漏口约60 m;沼气突破水封的危险性最大;泄漏后的...     

Psychrophilic and mesophilic anaerobic digestion of brewery effluent: a comparative study

Two expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactors (3.38 l active volume) were used to directly compare psychrophilic (15 degrees C), anaerobic digestion (PAD) to mesophilic (37 degrees C) anaerobic digestion (MAD) for the treatment of a brewery wastewater (chemical oxygen demand (COD) concentration of 3,136+/-891 mg l(-1)). Bioreactor performance was evaluated by COD removal efficiency and biogas yields at a range of hydraulic and organic loading rates. Specific methanogenic activity (SMA) assays were also employed to investigate the activity of the biomass in the bioreactors. No significant difference in the COD removal efficiencies (which ranged from 85-93%) were recorded between PAD and MAD during the 194-d trial at maximum organic and hydraulic loading rates of 4.47 kg m(-3) day(-1) and 1.33 m(3) m(-3) day(-1), respectively. In addition, the methane content (%) of the biogas was very similar. The volumetric biogas yield from the PAD bioreactor was approximately 50% of that from the MAD bioreactor at an organic loading rate of 4.47 kg COD m(-3) day(-3) and an applied liquid up-flow velocity (V(up)) of 2.5 m h(-1). Increasing the V(up) in the PAD bioreactor to 5 m h(-1) resulted in a volumetric biogas production rate of approximately 4.1 l d(-1) and a methane yield of 0.28 l CH(4) g(-1) COD d(-1), which were very similar to the MAD bioreactor. Significant and negligible biomass washout was observed in the mesophilic and psychrophilic systems, respectively, thus increasing the sludge loading rate applied to the former and underlining the robustness of the latter, which appeared underloaded. A psychrotolerant mesophilic, but not truly psychrophilic, biomass developed in the PAD bioreactor biomass, with comparable maximum SMA values to the MAD bioreactor biomass. PAD, therefore, was shown to be favourably comparable to MAD for brewery wastewater treatment and biogas generation.     

A comparison of wet and dry anaerobic digestion processes for the treatment of municipal solid waste and food waste

A main distinction between anaerobic digestion (AD) technologies for treatment of municipal and industrial biodegradable wastes is the operating process solids content. Wet AD systems operate at low total solids (<10–20% TS) and dry systems have high operating solids (20–>40% TS). The performance of wet and dry AD systems was quantified in relation to: technical operation (footprint, capacity, feedstock characteristics, pretreatment and post‐treatment, retention time, water usage), energy balance (biogas productivity, parasitic energy, methane [CH₄] content, utilization of biogas and produced energy), digestate management and economic performance (capital and operational costs, revenues, specific capital costs [per t of waste and per m³ biogas]). Wet AD plants had improved energy balance and economic performance compared to dry AD plants. However, dry AD plants offered several benefits, including greater flexibility in the type of feedstock accepted, shorter retention times, reduced water usage and more flexible management of, and opportunities for marketing, the end‐product.     

Biological sulphate removal from industrial effluent in an upflow packed bed reactor

A biological process for the removal of sulphate, using molasses as organic carbon source, is described. Sulphate is converted to sulphur via sulphide, and molasses to bicarbonate. Sulphate reducing bacteria are responsible for the reduction of sulphate to sulphide, while photosynthetic sulphur bacteria oxidize sulphide to elemental sulphur. It has been shown that these bacteria can live symbiotically in an upflow anaerobic packed bed reactor. The process is accompanied by the precipitation of calcium carbonate and heavy metal sulphides. Sulphate reduction follows zero order kinetics with respect to both reactants and products. The reduction of 1 g sulphate consumes 1.2 ml molasses and requires 6 h for completion. The optimum temperature for sulphate reduction was found to be 31°C.     

Performance characteristics of the anaerobic baffled reactor

An anaerobic sludge blanket process, termed the anaerobic baffled reactor (ABR), has been developed and shows promise for industrial wastewater treatment. It combines the advantages of high stability and reliability with a high void volume. The risk of clogging and sludge bed expansion with resulting high microbial losses is reduced and there is no need for special gas collection or biological solids separation systems. Organic loadings as high as 36 g COD l^?1day^?1 have been achieved with COD removal rates of more than 24 g COD l^?1 day^?1 and methane production rates exceeding 6 volumes per day per unit volume of reactor. The hypothesis, that the ABR may be adequately modeled as a fixed-film reactor, has been supported. Therefore, a unified approach, based on fundamentals of bacterial kinetics and mass transport, appears useful for modeling this and similar systems. Pilot plant studies are necessary to determine the scaling factors of the system as well as the overall efficiency and costs.     

Removal of organics from leachates by anaerobic filter

A laboratory-scale study was conducted on two anaerobic filters at several loading rates and four hydraulic detention times. Feed substrates were landfill leachates taken from a recently opened landfill (Keele Valley) and from an older site (Brock North) which had been closed for about 8 years. The strong raw leachate from the new landfill had a COD of 14,000 mg l⁻¹, a BOD/COD ratio of 0.7 and a COD/P value of 17,900. The partially stabilized leachate from the older landfill had a COD of only 3750 mg l⁻¹, a BOD/COD ratio of 0.3 and a COD/P value of 30,640.Results from the treatment of the two leachates were compared with those from a previous study of a “mature” landfill (Beare Road). It was demonstrated that the anaerobic filter could reduce the COD of leachate from landfills of different ages by 90%, at loading rates of 1.26–1.45 kg COD m⁻³ d⁻¹. Total biogas production ranged between 400 and 500 l gas kg⁻¹ COD destroyed and methane content between 75 and 85%. No phosphorus addition was required over the loading range studied.     

Methane production from industrial wastes by two-phase anaerobic digestion

Although much attention has been paid to energy recovery from municipal sewage, industrial liquid waste is a larger potential source of renewable energy. In certain industrial sectors it is possible, in theory to displace almost all of the purchased fuels by recovering the energy content of the waste in suitable forms and utilizing them within the plant. Anaerobic digestion is probably the only available process that can achieve the dual goal of energy recovery from aqueous wastes and stabilization of the pollution load. This paper presents data illustrating the limitations and vulnerability of the conventional digestion process to this end, and discusses the application and advantages of an innovative and advanced fermentation system, two-phase digestion. Results of operation of bench-, pilot- and full-scale two-phase digestion plants with several types of industrial liquid wastes are presented. Industrial sectors that could benefit from commercial-scale application of this new process are indicated.     

USR/UASB/好氧工艺处理酒糟废液及沼气高值利用

采用升流式固体厌氧反应器(USR)高温全糟发酵工艺处理高浓度酒糟废液并对沼气进行净化提纯,控制USR消化温度为55℃,反应器混合液碱度保持在3 000 mg/L左右,有机负荷为4 kgCOD/(m3.d),出水挥发酸一般在500 mg/L以下,pH值为6.7～7.6,单位池容产气量为1.8 m3/m3.USR/UASB/好氧处理工艺对COD的去除率＞99%,出水水质满足排放要求.沼气经过净化提纯后,甲烷含量达到98%、硫化氮含量＜20 mg/m3,实现了沼气的高值利用.     

The effects of organic toxicants on methane production and hydrogen gas levels during the anaerobic digestion of waste activated sludge

Batch serum bottle assays were conducted to examine the response of the anaerobic digestion process to inhibition induced by the pulse addition of four organic toxicants [chloroform, bromoethanesulfonic acid (BES), trichloroacetic acid (TCAA) and formaldehyde]. The impact that increasing levels of inhibition of methane production had on hydrogen response and volatile fatty acid (VFA) accumulation were examined. All of the toxicants, with the exception of formaldehyde, appeared to elicit similar hydrogen response patterns and VFA accumulations for similar levels of inhibition. Results indicate that both the hydrogen and acetate catabolizing methanogenic populations were inhibited to approximately the same extent by chloroform, BES, and TCAA. Severe inhibition of methane production (>70% reduction of methane produced compared to controls) resulted in a rapid accumulation of hydrogen in the gaseous headspace. When inhibition was less severe, hydrogen accumulated to levels only slightly above controls. Based on these preliminary results, there appears to be some limits on the potential of using hydrogen as an early warning indicator of process upset. Results do indicate, however, that monitoring hydrogen in consert with conventional process indicators should improve digester monitoring and may provide more rapid indication of process upsets due to toxic shocks.     

Comparing the anaerobic digestion of Ascophyllum nodosum,the organic fraction of municipal solid waste and white rice in batch reactors

The biogas potential of marine macroalga Ascophyllum nodosum was compared with the organic fraction of municipal solid waste (OFMSW) and white rice to determine the applicability of the feedstock for anaerobic digestion. For OFMSW three dry matter contents were compared, 3%, 10% and 25%, to determine the effect of dry matter on methane yield. Biogas was evolved in each system, but the rate of evolution of biogas changed with moisture content. The highest total methane yield was obtained from 3% OFMSW but A. nodosum yielded more methane at 176±37.62 L/kg VS than white rice and the drier anaerobic digestion of OFMSW. The substrates were digested using wastewater treatment plant inoculum to determine gas yield and gas quality under batch mesophilic digestion conditions.     

Microbiota in anaerobic digestion of sewage sludge with and without co‐substrates

In this study, seven full‐scale anaerobic digesters, with or without co‐substrate regime, were analysed by physicochemical and molecular biological methods. A combination of robust community fingerprinting and Illumina MiSeq sequencing revealed a core bacterial community dominated by Chloroflexi, Firmicutes, Bacteroidetes and Proteobacteria, with variations in the profiles because of differences in the co‐substrate feeding regime. Despite these differences, physicochemical properties revealed a stable performance of all reactors, indicating a resilient bacterial microbiota in all full‐scale reactors. A rich bacterial core community ensured reactor functionality, whilst feeding regime and reactor type impacted the overall and the core bacterial diversity. Within the Archaea, Methanosaeta dominated in all reactors. Results indicated no relationship between archaeal community structure and the type of co‐substrate digested. Methanogens rely on the metabolic end products of bacterial activity and are thus less dependent on differences in the initial co‐substrate regime.     

超声与碱预处理剩余污泥中温两相厌氧消化

以北方某污水处理厂(A/O工艺)剩余活性污泥为研究对象,考察了超声波与生石灰联合预处理对后续剩余污泥两相中温厌氧消化的影响,结果表明:两相反应器内污泥絮体被充分破坏,厌氧消化过程中在产酸相和产甲烷相内,NH3-N浓度均有提高,但是没有出现磷的显著释放。     

Biochemical effects of administering shock loads of sucrose to a laboratory-scale anaerobic (UASB) effluent treatment plant

An experimental study was undertaken to determine the effects of administering shock loads of sucrose to a laboratory-scale anaerobic effluent treatment plant (UASB reactor) treating diluted landfill leachate. Administration of shock loads of 10 g l⁻ sucrose caused accumulations of up to 7 g l⁻¹ of l-lactate and the resultant acidity caused the pH value of the reactor effluent to drop from 7.2 to 4.7 which inhibited methanogenesis.Major disturbances in the composition of the biogas also occurred and, under the severest conditions, the biogas contained up to 30% (v/v) hydrogen.     

Removal of organics and nutrients from food wastewater using combined thermophilic two-phase anaerobic digestion and shortcut biological nitrogen removal

A process combining pilot-scale two-phase anaerobic digestion and shortcut biological nitrogen removal (SBNR) was developed to treat organics and nutrients (nitrogen and phosphorus) from food wastewater. The thermophilic two-phase anaerobic digestion process was investigated without adjusting the pH of the wastewater for the pre-acidification process. The digested food wastewater was treated using the SBNR process without supplemental carbon sources or alkalinity. Under these circumstances, the combined system was able to remove about 99% of COD, 88% of TN, and 97% of TP. However, considerable amounts of nutrients were removed due to chemical precipitation processes between the anaerobic digestion and SBNR. The average TN removal efficiency of the SBNR process was about 74% at very low C/N (TCOD/TN) ratio of 2. The SBNR process removed about 39% of TP from the digested food wastewater. Conclusively, application of the combined system improved organic removal efficiency while producing valuable energy (biogas), removed nitrogen at a low C/N ratio, and conserved additional resources (carbon and alkalinity).     

Operating aerobic wastewater treatment at very short sludge ages enables treatment and energy recovery through anaerobic sludge digestion

Conventional abattoir wastewater treatment processes for carbon and nutrient removal are typically designed and operated with a long sludge retention time (SRT) of 10–20 days, with a relatively high energy demand and physical footprint. The process also generates a considerable amount of waste activated sludge that is not easily degradable due to the long SRT. In this study, an innovative high-rate sequencing batch reactor (SBR) based wastewater treatment process with short SRT and hydraulic retention time (HRT) is developed and characterised. The high-rate SBR process was shown to be most effective with SRT of 2–3 days and HRT of 0.5–1 day, achieving >80% reduction in chemical oxygen demand (COD) and phosphorus and approximately 55% nitrogen removal. A majority of carbon removal (70–80%) was achieved by biomass assimilation and/or accumulation, rather than oxidation. Anaerobic degradability of the sludge generated in the high-rate SBR process was strongly linked to SRT, with measured degradability extent being 85% (2 days SRT), 73% (3 days), and 63% (4 days), but it was not influenced by digestion temperature. However, the rate of degradation for 3 and 4 days SRT sludge was increased by 45% at thermophilic conditions compared to mesophilic conditions. Overall, the treatment process provides a very compact and energy efficient treatment option for highly degradable wastewaters such as meat and food processing, with a substantial space reduction by using smaller reactors and a considerable net energy output through the reduced aerobic oxidation and concurrent increased methane production potential through the efficient sludge digestion.