Fate of oestrogens during anaerobic blackwater treatment with micro-aerobic post-treatment.

The fate of oestrone (E1), 17beta-oestradiol (E2) and 17alpha-ethynyloestradiol (EE2) was investigated in a concentrated blackwater treatment system consisting of an UASB septic tank, with micro-aerobic post-treatment. In UASB septic tank effluent a (natural) total concentration of 4.02 microg/L E1 and 18.69 microg/L E2, comprising the sum of conjugated (>70% for E1 and >80% for E2) and unconjugated forms, was measured. During post-treatment the unconjugated oestrogens were removed to below 1 microg/L. A percentage of 77% of the measured unconjugated E1 and 82% of E2 was associated with particles >1.2 microm in the final effluent implying high sorption affinity of both compounds. When spiking the UASB septic tank effluent with E1, E2, EE2 and the sulphate conjugate of E2, removal in the micro-aerobic post-treatment was >99% for both E2 and EE2 and 83% for E1. The lower removal value for E1 was a result of (slow) deconjugation during the treatment, and in the final effluent still 40% of E1 and 99% of E2 was present in conjugated form. The latter was the result of incomplete deconjugation of the spiked E2(3S) in the post-treatment system.     

The impact of increasing energy crop addition on process performance and residual methane potential in anaerobic digestion.

In a full-scale agricultural biogas plant, the changes in process performance connected with the increasing energy crop addition were monitored. The substrates applied were pig manure, solid energy crops and agricultural residues. During the study, the organic loading rate and the volume-related biogas productivity were doubled to 4.2 kg VS/(m(.3)d) and 2.83 Nm(3)/(m(3).d) respectively, by means of increasing the energy crop ratio in the feedstock to 96.5% (volatile solids). This resulted in an increase of the electrical capacity on a level twice as high as before. At the same time, methane yield and organic degradation rate decreased slightly to 0.35 Nm(3)/kg VS(added) and 87.4%, respectively. The strongest impact observed was on the transfer of partly degraded organic material into the digestate storage and with this, an increase of the residual methane potential of the digestate. A maximum theoretical methane load in the digestate of 14.4% related to total methane production of the biogas plant was observed. This maximum level could be reduced to 5.5%.     

Influence of the addition of sulphate and ferric ions in a methanogenic anaerobic packed-bed reactor treating gasoline-contaminated water.

Benzene, toluene and xylene (BTX) are relatively soluble aromatic compounds of gasoline. Gasoline storage tank leakages generally lead to an extensive contamination of groundwater. In the natural environment for instance, these compounds might be biodegraded under a variety of reducing potentials. The objective of this work was to examine the influence of the addition of sulphate and Fe(OH)3 in a methanogenic horizontal-flow anaerobic immobilized-biomass reactor treating gasoline-contaminated water. Three different conditions were evaluated: methanogenic, sulphidogenic and sulphidogenic with the addition of ferric ions. Methanogenic condition showed the higher BTX degradation rates and the addition of sulphate negatively affected BTX removal rates with the production of H2S. However, the addition of ferric ions resulted in the precipitation of sulphur, improving BTX degradation by the consortium. Metanosphaera sp., Methanosarcina barkeri and Methanosaeta concilii were identified in the consortium by means of 16S and directly related to the addition of ferric ions.     

串联厌氧生物滤池处理城市污水的试验研究

对常温下采用弹性立体填料的厌氧生物滤池和采用砾石填料的厌氧生物滤池串联处理生活污水的适用性、设计运行参数及环境因素的影响进行了研究。结果表明,用污水处理厂二沉池回流污泥对厌氧生物滤池进行接种后,利用污水处理厂钟式沉砂池作为原水,厌氧生物滤池可以在常温（18～25℃）条件下成功启动,有效地去除有机物,并且能承受水质水量波动引起的负荷冲击。除处理出水除氮磷等指标外．其余指标均能达到污水综合排放一级标准。     

Combining biocatalyzed electrolysis with anaerobic digestion.

Biocatalyzed electrolysis is a microbial fuel cell based technology for the generation of hydrogen gas and other reduced products out of electron donors. Examples of electron donors are acetate and wastewater. An external power supply can support the process and therefore circumvent thermodynamical constraints that normally render the generation of compounds such as hydrogen unlikely. We have investigated the possibility of biocatalyzed electrolysis for the generation of methane. The cathodically produced hydrogen could be converted into methane at a ratio of 0.41 mole methane mole(-1) acetate, at temperatures of 22+/-2 degrees C. The anodic oxidation of acetate was not hampered by ammonium concentrations up to 5 g N L(-1). An overview is given of potential applications for biocatalyzed electrolysis.     

Application of enzymes in anaerobic digestion.

Owing to the very low economic value of brewer's spent grains, its utilisation for biogas production is very promising. The hydrolysis of ligno-cellulose is the rate limiting step in anaerobic digestion. Enzymatic pre-treatment promotes the hydrolysis of ligno-cellulose, breaking it down to lower molecular weight substances which are ready to be utilised by the bacteria. A cheap raw multi-enzyme produced by a solid state fermentation (SSF) process is a good substitute for expensive conventional enzyme. The SSF enzyme application to spent grain has been investigated by carrying out enzymatic solubility tests, hydrolytic experiments and two-step anaerobic fermentation of spent grain. Gas chromatograph analysis was conducted to quantify fatty acids concentrations, while CH(4), CO(2), O(2), H(2) and H(2)S were measured to determine biogas quality by means of a gas analyser. DS, oDS, pH were also measured to analyse the anaerobic digestion. The result shows that enzyme application promotes the hydrolysis of ligno-cellulose, indicated by higher enzymatic solubility and fatty acid concentration in a hydrolytic bioreactor. Moreover, biogas production is also increased. The quality of the gases produced is also enhanced. Since the anaerobic digestion can be operated in a stable performance, it can also be concluded that SSF enzyme is compatible with anaerobic digestion.     

High-rate stormwater clarification with polymeric flocculant addition.

Treatment of urban stormwater by clarification, with flocculant addition, was studied in Toronto, Canada using a pilot-scale clarifier with removable lamellar plates. Almost 90 stormwater runoff events were characterised at the study site and found fairly polluted. The previous research phase indicated good treatability of this stormwater by lamellar clarification with flocculant addition (total suspended solids, TSS, removal of 84%, at a surface load of 15 m/h), but there were concerns about cleaning plates after storm events. With the aid of numerical modelling, hydraulic improvements to the clarifier inlet zone were retrofitted in 2004 and permitted the removal of the lamellar pack without a loss in treatment efficiency. In the modified clarifier, a cationic polymeric flocculant dosage of 4 mg/L with conventional clarification provided a TSS removal of 77%, at surface loads up to 43 m/h. The use of the polymer did not increase the acute toxicity of the treated effluent. The clarifier sludge was severely polluted by several heavy metals and would require special disposal. The treatment process tested could be well applied in projects requiring intensive stormwater treatment at compact sites.     

Nitrogen removal from piggery waste with anaerobic pretreatment.

Aerobic degradation of high strength piggery waste elevated the reactor temperature inhibiting nitrification. This study included anaerobic pretreatment with various influent by-pass rates to control the temperature and to minimize the external carbon requirement for denitrification. To find the optimum operating conditions, both lab-scale AnSBR (anaerobic sequencing batch reactor) and Ax/Ox (anoxic/oxic) SBR were operated at 35 degrees C. The heat energy released from Ax/Ox SBR was assumed to be used for heating the AnSBR, with which the Ax/Ox reactor temperature could successfully be controlled below 40 degrees C. The optimum rates of by-pass were 1.0 for winter, 0.4 for spring/fall and 0.2-0.4 for summer, respectively. Applying the correction factors for the measured AUR2 (nitrite nitrification rate) and AUR (nitrate nitrification) at the predicted temperatures, the required oxic HRTs were computed. The required Ax/Ox HRT ratios were respectively 0.5 for COD/TKN>8, 1.0 for COD/TKN ratio of 5.5-8 and 3.5 for below 5.5. The optimum HRTs were 16 days for AnSBR and 17 days for Ax/Ox SBR with the corrected AUR2.     

Thermophilic anaerobic digester with ultrafilter for solids stabilization.

A thermophilic anaerobic digester with ultrafilter (TADU) for solids separation offers potential advantages of higher VS destruction, biomass retention, and pathogen removal. However, potential disadvantages include ultrafilter fouling, decreasing flux, and high VFA concentrations. In this study, a thermophilic anaerobic digester coupled to a sintered titanium, cross-flow ultrafilter was operated for over five months. Dairy manure was digested (HRT of 23 days). The filtrate VFA concentration was low (220 mg/L as HAc), average VS destruction was 49%, and a low average effluent fecal coliform concentration of 10(2) MPN/100 mL was observed. The low coliform value may be beneficial if dewatered biosolids are used for livestock bedding since low pathogen counts help prevent mastitis. Ultrafilter fluxes of 40-80 L/m2-hr were maintained by cleaning using caustic (3.5% NaOH) followed by water and acid (3% phosphoric acid). Sand from livestock bedding was found to damage the pump and ultrafilter. If TADU were implemented at full scale, then replacing sand bedding with dewatered biosolids should be considered.     

Roles of methanogens on volatile organic sulfur compound production in anaerobically digested wastewater biosolids.

Land application of wastewater biosolids is both economical and beneficial to resource recycling. However, this environmentally friendly practice can be at risk due to odor complaints. Volatile organic sulfur compounds (VOSCs) including methanethiol, dimethyl sulfide, and dimethyl disulfide, have been identified as major contributors to biosolids odor. In this study, methanogens were shown to play a key role in removing VOSCs and reducing odors, and methane production was related to reduced VOSC production. Factors influencing the growth of methanogens such as the shear during dewatering and storage temperature showed a strong impact on net odor production. Examination of the microbial communities of both bacteria and archaea indicated a simplified archaeal community in biosolids, which is susceptible to environmental perturbations. Therefore, one possible odor control strategy is the preservation and enhancement of the methanogenic population during biosolids storage.     

Concentration of nutrients from urine and reject water from anaerobically digested sludge.

Experiments with concentration of nutrients from source separated urine and reject water from digestion of sludge in sewage treatment plants (STP) have been performed in laboratory and pilot scale. The methods tested were membrane filtration with reverse osmosis (RO), evaporation, and precipitation of phosphorus and distillation of ammonia. In membrane filtration, pre-filtration with particle separation at 5-10 microm was enough to avoid clogging of the membranes. Separation of phosphorus (P), potassium (K) and sulphur (S) was almost 100%, while separation of nitrogen (N) was dependent on pH. The capacity of flux increased with temperature and pressure. In evaporation, all P, K and S were still in the concentrate, while pH had to be decreased to 4.5 to avoid significant loss of N. In precipitation and distillation, about 90% of P could be recovered from urine as magnesium ammonium phosphate (MAP) just by adding MgO. For the reject water pH was first increased by aeration to remove CO2. Ammonium can be distilled from the water phase after precipitation of MAP, without further increase of pH. At least 80-90% of N can be distilled in 5-10% of the total volume. The article also discusses the quality of different products, cost of separation, and energy and chemical demand.     

Instrumentation in anaerobic treatment--research and practice.

High rate anaerobic treatment reactors are able to uncouple solids and liquid retention time, resulting in high biomass concentrations. Principal advantages of anaerobic treatment include: energy efficiency, low biomass yield, low nutrient requirement and high volumetric organic loadings. In order to facilitate small reactors operation with stable and good performance automatic process control systems in combination with on-line instrumentation are proposed. The paper reviews the development and availability of the principal instrumentation for anaerobic treatment processes. First, the most important measuring principles are discussed, followed by a review of the most important process variables with emphasis on the development of their instrumental measurement techniques and application in research. Finally, a summary of actual application of instrumentation in full-scale anaerobic treatment plants is presented.     

Application of Methanobrevibacter acididurans in anaerobic digestion.

To operate anaerobic digesters successfully under acidic conditions, hydrogen utilizing methanogens which can grow efficiently at low pH and tolerate high volatile fatty acids (VFA) are desirable. An acid tolerant hydrogenotrophic methanogen viz. Methanobrevibacter acididurans isolated from slurry of an anaerobic digester running on alcohol distillery wastewater has been described earlier by this lab. This organism could grow optimally at pH 6.0. In the experiments reported herein, M. acididurans showed better methanogenesis under acidic conditions with high VFA, particularly acetate, than Methanobacterium bryantii, a common hydrogenotrophic inhabitant of anaerobic digesters. Addition of M. acididurans culture to digesting slurry of acidogenic as well as methanogenic digesters running on distillery wastewater showed increase in methane production and decrease in accumulation of volatile fatty acids. The results proved the feasibility of application of M. acididurans in anaerobic digesters.     

Influence of hydraulic retention time on UASB post-treatment with UF membranes

A pilot UASB reactor coupled with an external ultrafiltration (UF) membrane was operated under three different hydraulic retention times (HRT) for domestic wastewater treatment. The aim was to assess the HRT influence on system performance and fouling. The highest concentrations of COD, total solids, extracellular polymeric substances (EPS) and soluble microbial products (SMP) in UASB effluent and permeate were found when the UASB reactor was operated under the lowest HRT studied (4 hours); although the fulfillment of Mexican Standard for wastewater reclamation was not compromised. This fact could be attributed to the higher shear stress forces inside the UASB reactor when it was operated at low HRT, which promoted the release of biopolymeric substances in its effluent. Besides, the fouling propensity in the UASB effluent was worsened with HRT reduction, by increasing the fouling rate and the specific cake resistance. Based on these results, it is recommended to avoid operating the UASB reactor at low HRTs (less than 4 hours) in order to control SMP and EPS fouling potential. The results presented also suggest that HRT reduction has a detrimental effect on performance and fouling.     

Wastewater treatment with anaerobic membrane bioreactor and reverse osmosis.

Domestic wastewater from a new city district in Stockholm has been treated by an anaerobic membrane bioreactor (AMBR) followed by reverse osmosis (RO). The main objectives were to study the gas production, the reduction of organic matter and nutrient recovery. The AMBR was operated at 22 degrees C (equal to the average temperature in the influent) and a hydraulic retention time of 0.6 d. The results show that the reduction of organic matter, nitrogen and phosphorus over the AMBR was approximately 92, 9 and 9%, respectively. A stable gas production was registered throughout the evaluation period. The overall removal efficiency, i.e. including the RO, was >99% for TOC, >91% for Kj-N and about 99% for P. Adding a reverse osmosis (RO) unit to the AMBR makes it possible to produce a concentrated, nutrient rich product well suited for agricultural use. The quality of the concentrate is, in terms of nutrient concentration and heavy metal content, similar to source separated human urine, i.e. nitrogen content about 3 g N/L and <2 mg Cd/kg P. However, addition of acid is required to prevent precipitation/fouling of the RO. The total electricity use for operation for the system, including the RO-unit, is estimated to be 3-6 kWh/m3.     

Multidimensional modelling of anaerobic granules.

A multispecies, two- and three-dimensional model was developed, based on a previously published planar biofilm model, and the biochemical structure of the ADM1. Several soluble substrates diffuse and react in the granule. Local pH is calculated from acid-base equilibria and charge balance. The model uses individual-based representation of biomass particles within the granule (biofilm), and describes spreading by an iterative pushing technique. The overall computational domain consists of one granule, and is divided into a grid with Cartesian coordinates. The number of grid elements does not limit the number of biomass particles, and it is not necessary to use grid-spreading techniques, such as cellular automata, which result in Cartesian artefacts. The model represents both microscopic and macroscopic features in granule structure, previously observed using in-situ molecular techniques, and can be effectively used to interpret these results.     

Use of an anaerobic sequencing batch reactor for parameter estimation in modelling of anaerobic digestion.

The model structure in anaerobic digestion has been clarified following publication of the IWA Anaerobic Digestion Model No. 1 (ADM1). However, parameter values are not well known, and uncertainty and variability in the parameter values given is almost unknown. Additionally, platforms for identification of parameters, namely continuous-flow laboratory digesters, and batch tests suffer from disadvantages such as long run times, and difficulty in defining initial conditions, respectively. Anaerobic sequencing batch reactors (ASBRs) are sequenced into fill-react-settle-decant phases, and offer promising possibilities for estimation of parameters, as they are by nature, dynamic in behaviour, and allow repeatable behaviour to establish initial conditions, and evaluate parameters. In this study, we estimated parameters describing winery wastewater (most COD as ethanol) degradation using data from sequencing operation, and validated these parameters using unsequenced pulses of ethanol and acetate. The model used was the ADM1, with an extension for ethanol degradation. Parameter confidence spaces were found by non-linear, correlated analysis of the two main Monod parameters; maximum uptake rate (k(m)), and half saturation concentration (K(S)). These parameters could be estimated together using only the measured acetate concentration (20 points per cycle). From interpolating the single cycle acetate data to multiple cycles, we estimate that a practical "optimal" identifiability could be achieved after two cycles for the acetate parameters, and three cycles for the ethanol parameters. The parameters found performed well in the short term, and represented the pulses of acetate and ethanol (within 4 days of the winery-fed cycles) very well. The main discrepancy was poor prediction of pH dynamics, which could be due to an unidentified buffer with an overall influence the same as a weak base (possibly CaCO3). Based on this work, ASBR systems are effective for parameter estimation, especially for comparative wastewater characterisation. The main disadvantages are heavy computational requirements for multiple cycles, and difficulty in establishing the correct biomass concentration in the reactor, though the last is also a disadvantage for continuous fixed film reactors, and especially, batch tests.     

常温厌氧生物滤池处理生活污水原理与技术

介绍厌氧生物处理的基本原理、温度对厌氧处理的影响和厌氧生物滤池处理技术的特点,综述了国内常温厌氧生物滤池处理生活污水技术的研究成果.为了解决常温厌氧生物滤池脱氮除磷效率低、出水N、P浓度高的问题,提出常温厌氧生物滤池组合人工湿地或人工土地渗滤处理工艺的设想,在不曝气的条件下,满足高标准的出水需求,降低能耗.     

Modeling of anaerobic treatment of wastewater in ponds.

A mathematical model to simulate the performance of anaerobic ponds was developed incorporating both settling of particulate components and the biological anaerobic digestion process. The biological activity includes solubilization of particulate organic matter; methanogenesis and the sulphate reduction process. The model considers that an anaerobic pond comprises a series of equal size columns. Each column has three compartments viz. liquid layer, active sediment layer and inert sediment layer. The existence of organic matter and sulphate removal mechanisms both in the bulk as well as sediment layer of the ponds and the exchange of the soluble components between the layers has been included in the model. The model was transferred to a computer program using VisSim Basic software. The model was verified by comparing simulated results with full-scale as well as with laboratory-scale anaerobic pond performance data. A good agreement between the simulated and the observed pond performance was achieved.     

Prion protein: detection in 'spiked' anaerobic sludge and degradation experiments under anaerobic conditions.

The behavior of the transmissible spongiform encephalopathies (TSE) causing agent denominated "prion protein" in anaerobic sludge (biogas reactor) was assessed with incubation tests. A widely applied screening method for BSE in cattle on the basis of the Western blotting protocol was adapted to detect the Proteinase K resistant, scrapie-form prion protein (PrPSC). As PrPsc source homogenized TSE infected brain tissue of animals late in the clinical phase of disease was taken (301V/VM mouse-BSE; bovine BSE and 22A/SV mouse-scrapie). The incubation under mesophilic conditions did not show any significant reduction of the PrPsc titer. Under thermophilic conditions contradictory results were obtained. The reduction time of PrPsc in water was equal to or longer than the PrPsc reduction time in anaerobic sludge. In comparison, with sterilized (121 degrees C, steam pressure) or poisoned (sodium azide, 1% w/v) sludge used as incubation matrix a much shorter time resulted until no prion protein could be detected.