Phenolic refinery wastewater biodegradation by an expanded granular sludge bed reactor.

Refinery spent caustics (SC) were diluted with sour waters (SW) in a ratio 1:7, neutralized with CO2 (SC/SW(CO2)) and 83% of H2S was striped during this procedure, remaining an aromatic portion that contained 2123, 2730 and 1379 mg L(-1) of phenol, p-cresol and o-cresol, respectively. The mixture was teated anaerobically in an EGSB reactor fed with 1.5 gCOD L(-1) d(-1), without mineral supplements causing loss of COD removal efficiency that dropped to 23%, methane production ceased and no phenol or cresols were biodegraded. The EGSB experiments were resumed by feeding the reactor with nutrients and phenol at 1.0 gCOD L(-1) d(-1). The mixture SC/SWco2 added to the phenol load, was step increased from 0.10 to 0.87 gCODL(-1) d(-1) maximum. When total organic load was increased to 1.6, COD removal efficiency was 90% and at the highest load attained, 1.87, efficiency dropped to 23% attributed to the toxic effect produced by cresols.     

厌氧颗粒污泥悬浮床反应器的研究与应用

提出厌氧复合循环颗粒污泥悬浮床反应器的新型反应器理论.通过引入分级三相分离器,使悬浮床反应器上部处理区液体和沼气的上升速度大大降低,创造了污泥颗粒沉降的良好环境.底部利用高负荷产生的沼气形成内循环,同时设置外回流系统,内、外循环实现了进水与颗粒污泥间的充分接触及保持了良好的反应条件,创造了大幅度提高CODCr容积负荷的条件.对反应器的启动、运行和在不同负荷条件下的去除效果和悬浮流态进行了研究.研究表明,厌氧颗粒污泥悬浮床反应器处理淀粉废水,可在负荷30～40 kg CODCr/(m3·d)条件下稳定运行,最高负荷达57.2kgCODCr/(m3·d),平均CODCr去除率可达90%.     

厌氧颗粒污泥悬浮床反应器的理论基础初探

从反应器理论上对现有高效厌氧反应器流动状态进行研究和分析,认为化工过程理论提出的膨胀床和流化床之间实际上还存在着一个过渡区。经过对反应器过渡区流动状态细致研究,提出悬浮床反应器的概念。重点讨论厌氧悬浮床反应器理论,并通过上流式厌氧污泥床运行模式的实际反应器运行分析,从试验角度证实厌氧悬浮床反应器流动状态的优越性。     

Full scale fluidized bed anaerobic reactor for domestic wastewater treatment: performance, sludge production and biofilm.

This paper describes the performance, sludge production and biofilm characteristics of a full scale fluidized bed anaerobic reactor (32 m3) for domestic wastewater treatment. The reactor was operated with 10.5 m x h(-1) upflow velocity, 3.2 h hydraulic retention time, and recirculation ratio of 0.85 and it presented removal efficiencies of 71+/-8% of COD and 77+/-14% of TSS. During the apparent steady-state period, specific sludge production and sludge age in the reactor were (0.116+/-0.033) kgVSS. kgCOD(-1) and (12+/-5)d, respectively. Biofilm formed in the reactor presented two different patterns: one of them at the beginning of the colonization and the other of mature biofilm. These different colonization patterns are due to bed stratification in the reactor, caused by the difference in local-energy dissipation rates along the reactor's height, and density, shape, etc. of the bioparticles. The biofilm population is formed mainly of syntrophic consortia among sulfate reducing bacteria, methanogenic archaea such as Methanobacterium and Methanosaeta-like cells.     

ABR处理淀粉废水的反应规律研究

研究了厌氧折流板反应器(ABR)启动阶段在不同的水力条件和容积负荷下,对有机负荷为1.2～3.6kgCODCr/(m3·d)淀粉溶液的CODCr去除率,以及ABR工艺运行过程中的影响因素进行分析。初步研究结果表明,在启动阶段中低负荷反应条件下①HRT12h、CODCr600mg/L、容积负荷1.2kgCODCr/(m3·d);②HRT12h、CODCr1200mg/L、容积负荷2.4kgCODCr/(m3·d);③HRT8h、CODCr1200mg/L、容积负荷3.6kgCODCr/(m3·d),ABR反应器对CODCr均有较高的去除率。运行稳定后,ABR反应器的CODCr去除率在80%左右,扫描电镜检测结果表明各隔室中的微生物以球菌为主。研究表明ABR工艺是一种运行稳定、高效率的有机废水处理技术。     

Aerobic granular sludge in an SBR-system treating wastewater rich in particulate matter.

Aerobic granular sludge was successfully cultivated in a lab-scale SBR-system treating malting wastewater with a high content of particulate organic matter (0.9 gTSS/L). At an organic loading rate (CODtotal) of 3.4 kg/(m3 x d) an average removal efficiency of 50% in CODtotal and 80% in CODdissolved was achieved. Fractionation of the COD by means of particle size showed that particles with a diameter less than 25-50 microm could be removed at 80% efficiency, whereas particles bigger than 50 microm were only removed at 40% efficiency. Tracer experiments revealed a dense sessile protozoa population covering the granules. The protozoa appeared to be responsible for primary particle uptake from the wastewater.     

Optimizing sequencing batch reactor (SBR) reactor operation for treatment of dairy wastewater with aerobic granular sludge

The biological wastewater treatment using aerobic granular sludge is a new and very promising method, which is predominantly used in SBR reactors which have higher volumetric conversion rates than methods with flocculent sludge. With suitable reactor operation, flocculent biomass will accumulate into globular aggregates, due to the creation of increased substrate gradients and high shearing power degrees. In the research project described in this paper dairy wastewater with a high particle load was treated with aerobic granular sludge in an SBR reactor. A dynamic mathematical model was developed describing COD and nitrogen removal as well as typical biofilm processes such as diffusion or substrate limitation in greater detail. The calibrated model was excellently able to reproduce the measuring data despite of strongly varying wastewater composition. In this paper scenario calculations with a calibrated biokinetic model were executed to evaluate the effect of different operation strategies for the granular SBR. Modeling results showed that the granules with an average diameter of 2.5 mm had an aerobic layer in between 65-95 microm. Density of the granules was 40 kgVSS/m3. Results revealed amongst others optimal operation conditions for nitrogen removal with oxygen concentrations below 5 gO2/m3. Lower oxygen concentrations led to thinner aerobic but thicker anoxic granular layers with higher nitrate removal efficiencies. Total SBR-cycle times should be in between 360-480 minutes. Reduction of the cycle time from 480 to 360 minutes with a 50% higher throughput resulted in an increase of peak nitrogen effluent concentrations by 40%. Considering biochemical processes the volumetric loading rate for dairy wastewater should be higher than 4.5 kgCOD/(m3*d). Higher COD input load with a COD-based volumetric loading rate of 9.0 kgCOD/(m3*d) nearly led to complete nitrogen removal. Under different operational conditions average nitrification rates up to 5 gNH/(m3*h) and denitrification rates up to 3.7 gNO/(m3*h) were achieved.     

Behaviour of a full-scale expanded bed reactor with overlaid anaerobic and aerobic zones for domestic wastewater treatment.

This paper presents the behaviour of a full-scale expanded bed reactor (160 m3) with overlaid anaerobic and aerobic zones used for municipal wastewater treatment. The research was carried out in two experimental steps: anaerobic and anaerobic-aerobic conditions, and the experimental results presented in this paper refer to four months of reactor operation. In the anaerobic condition, after inoculation and 60 days of operation, the reactor treating 3.40 kg CODm(-3)d(-1) for thetaH of 2.69 h, reached mean removal efficiencies of 76% for BOD, 72% for COD, and 80% for TSS, when the effluent presented mean values of 225 mg.L(-1) of COD, 98 mg.L(-1) of BOD and 35 mg.L(-1) of TSS. Under these conditions, for nitrogen loading of 0.27 kgN.m(-3)d(-1), the reactor generated an effluent with mean N-org. of 8 mg.L(-1) and N-ammon. of 37 mg.L(-1), demonstrating high potential of ammonification. For the anaerobic-aerobic condition (118th day) the system was operated with thetaH of 5.38 h presented mean removal efficiencies of 84% for BOD, 79% for COD, 76% for TSS, and 30% for TKN. The reactor's operation time was less than two months, which was not long enough to reach nitrification. Regarding the obtained results, this research confirmed that this reactor is configured as a flexible and adequate alternative for the treatment of sewage, requiring relatively small area and only thetaH of 10 h that can be adjusted to the local circumstances.     

Effects of ORP, recycling rate, and HRT on simultaneous sulfate reduction and sulfur production in expanded granular sludge bed (EGSB) reactors under micro-aerobic conditions for treating molasses distillery wastewater

An expanded granular sludge bed (EGSB) reactor was adopted to incubate the sludge biogranule that could simultaneously achieve sulfate reduction and sulfide reoxidization to elemental sulfur for treating molasses distillery wastewater. The EGSB reactor was operated for 175 days at 35 °C with a pH value of 7.0, chemical oxygen demand (COD) loading rate of 4.8 kg COD/(m3 d), and sulfate loading rate of 0.384 kg SO(4)(2-)/(m3 d). The optimal operation parameters, including the oxidation reduction potential (ORP), recycling rate, and hydraulic retention time (HRT), were established to obtain stable and acceptable removal efficiencies of COD, sulfate, and higher elemental sulfur production. With an ORP of -440 mV, a recycling rate of 300%, and HRT of 15 h, the COD and sulfate removal efficiencies were 73.4 and 61.3%, respectively. The elemental sulfur production ratio reached 30.1% when the elemental sulfur concentration in the effluent was 48.1 mg/L. The performance results were also confirmed by the mass balance calculation of sulfate, sulfide, and elemental sulfur over the EGSB reactor.     

Anaerobic biodegradation of 2,4,6-trichlorophenol in expanded granular sludge bed and fluidized bed biofilm reactors bioaugmented with Desulfitobacterium spp

The biodegradation of 2,4,6-trichlorophenol (246TCP) was studied using expanded granular sludge bed (EGSB) reactors and a fluidized bed biofilm reactor (FBBR) filled with activated carbon. One of the EGSB reactor and the FBBR were bioaugmented with Desulfitobacterium strains. 246TCP loading rate was gradually incremented from 10 to 250 mg L(-1) day(-1). The main pathway of dechlorination was in ortho-position, generating 4-chlorophenol and 2,4-dichlorophenol. The maintenance of both COD degradation efficiency (higher than 80%) and methanogenic efficiency (between 0.3 and 0.6 g CH4-COD g(-1) COD consumed) in EGSB reactor implies a great stability of the process. Through isotherm studies in FBBR, it could be deduced that around 52% of 246TCP was completely dechlorinated, whereas the adsorption involved around 16%. By means of FISH studies it was proved that the methanogenic Archaea community was maintained in the bioaugmented EGSB reactor, whereas in the FBBR this community was gradually developed until reaching stability. Desulfitobacterium community was also maintained in the reactors, although D. chlororespirans proportion rise in the FBBR at the higher 246TCP loading rates, implying that this species can withstand the 246TCP toxicity better than D. hafniense.     

Study on performance of granular ANAMMOX process and characterization of the microbial community in sludge.

Anaerobic Ammonium Oxidation (ANAMMOX) is a novel biological nitrogen removal process, which is regarded as the most economical process at present. In this paper, two lab-scale UASB reactors, one of which was inoculated with the mixture of anaerobic sludge and aerobic sludge, the other with river sediments, were started up, using the inorganic synthetic water containing ammonium and nitrite as influent. After 421 days' and 356 days operation respectively, the ammonium removal efficiencies in two reactors reached 94% and 86% respectively, the total nitrogen volumetric loading rates were 2.5 and 1.6 kgN/m3 x d. ANAMMOX granules were obtained in both reactors; the color of most granules was brown, but some of them were red. Based on the observation and studies on the microstructure of the granules, three kinds of ANAMMOX granular sludge formation mechanisms were proposed: adhering biofilm and disintegrated granular core mechanism, adhering biofilm and inorganic core mechanism and the self-coherence mechanism. For phylogenetic characterization of anaerobic ammonium oxidizers, 16S rDNA approach was performed using Planctomycetales-specific PCR amplification. The dominant anammox bacteria occupied more than 90% of Planctomycetales-specific bacteria, and 27% of all bacteria in reactors. The dominant anammox bacteria distantly related to all currently reported candidate anammox genera. Functional gene of amoA was analyzed to investigate the 'aerobic' ammonium-oxidizing bacteria in beta-Proteobacteria. The 'aerobic' ammonium-oxidizing bacteria were more diverse than anammox bacteria, but most of them clustered in anoxic ammonium-oxidizing Nitrosomonas eutropha/europaea groups. The composition of 'aerobic' ammonium-oxidizing bacteria is only 2% of all of bacteria in reactors.     

Characteristics of granular sludge in a single upflow sludge blanket reactor treating high levels of nitrate and simple organic compounds.

Simultaneous denitrification and methanogenesis were accomplished in a single upflow sludge blanket (USB) reactor. More than 99% and 95% of nitrate and chemical oxygen demand (COD) removal rates were obtained at a loading of 600 mg NO3-N/L x d and 3,300 mg COD/L x d, respectively. The specific denitrification rate (SDR) increased as COD/NO3-N ratios decreased. Maximum SDR with acetate could reach 1.05 g NO3-N/gVSS x d. Significant sludge flotation was observed at the top of the reactor due to the change of microbial composition and the formation of hollow granules. Granules became fluffy and buoyant due to the growth of denitrifiers. Microscopic examination showed that granules exhibited layered structure and they were mainly composed of Methanosarcina sp., Pseudomonas sp., and rod-shaped bacteria.     

Optimising the performance of a lab-scale tidal flow reed bed system treating agricultural wastewater.

A gravel-based tidal flow reed bed system was operated with three different strategies in order to investigate its optimal performance for the treatment of a high strength agricultural wastewater. According to the three strategies, individual reed beds were saturated and unsaturated with the wastewater for different periods while reasonably stable hydraulic and organic loadings were maintained. Experimental results demonstrated that the system produced the highest pollutant removal efficiencies with a relatively short saturated period and long unsaturated period, highlighting the importance of oxygen transfer into reed bed matrices during the treatment. Significant removals of some major organic and inorganic pollutants were achieved under all three operational conditions. Nitrification was not the major route of ammoniacal-nitrogen removal when the system was under high organic loading. Due to the filtration of suspended solids and the accumulation of biomass, gradual clogging of the reed bed matrices took place, which caused concerns over the long-term efficiency of the tidal flow system.     

HSBR反应器处理生活污水的试验研究

研究了新型不完全厌氧反应器———不完全厌氧序批式反应器 (HSBR)处理生活污水的特性。在容积负荷 0 4 1～ 0 6 3kgCOD/ (m3·d)的运行条件下 ,取得了 75 %以上的COD去除率 ;在2 77kgCOD/ (m3·d)的冲击负荷下 ,取得 35 %的COD去除率。同时研究了反应时间以及混合强度对COD去除率的影响 ,并分析了不完全厌氧反应器取得良好处理效果的原因。     

Aerobic granular sludge: a promising technology for decentralised wastewater treatment.

In order to evaluate the characteristics of aerobic granular sludge, a sequencing batch reactor, feeding with synthetic wastewater at the organic loading rate of 8 kg COD/m3 d, was employed on the laboratory scale. Granules occurred in the reactor within 1 week after the inoculation from conventional flocculent sludge. Aerobic granular sludge was characterised by the outstanding settling properties and considerable contaminates removal efficiencies. The SVI30 values were in the range of 20 to 40 ml g(-1). However, the sludge volume index of short settling time (e.g. SVI10--10 min) is suggested to describe the fast settling properties of aerobic granular sludge. The potential application in the decentralised system is evaluated from the point view of footprint and high bioactivity. The occurrence of sloughing, resulting from the outgrowth of filamentous organisms, would be responsible for the instability of aerobic granules. The starvation phase should therefore be carefully controlled for the maintenance and stability of aerobic granular sludge system.     

Comparing the performance of UASB and GRABBR treating low strength wastewaters

Anaerobic technologies have proved successful in the treatment of various high strength wastewaters with perceptible advantages over aerobic systems. The applicability of anaerobic processes to treat low strength wastewaters has been increasing with the evolution of high-rate reactors capable of achieving high sludge retention time (SRT) when operating at low HRT. However, the performance of these systems can be affected by high variations in flow and wastewater composition. This paper reports on the comparative study carried out with two such high rate reactors systems to evaluate their performances when used for the treatment of low strength wastewaters at high hydraulic rates. One of the two systems is the most commonly used upflow anaerobic sludge blanket (UASB) reactor in which all reactions occur within a single vessel. The other is the granular bed baffled reactor (GRABBR) that encourages different stages of anaerobic digestion in separate vessels longitudinally across the reactor. The reactors, with equal capacity of 10 litres, were subjected to increasing organic loading rates (OLRs) and hydraulic retention times (HRTs) of up to 60 kg COD m(-3) d(-1) and 1 h respectively. Results show that the GRABBR has greater processes stability at relatively low HRTs, whilst the UASB seems to be better equipped to cope with organic overloads or shockloads. The study also shows that the GRABBR enables the harvesting of biogas with greater energetic value and hence greater re-use potential than the UASB. Biogas of up to 86% methane content is obtainable with GRABBR treating low strength wastewaters.     

Biological sludge solubilisation for reduction of excess sludge production in wastewater treatment process.

A novel sludge disintegration system (JFE-SD system) was developed for the reduction of excess sludge production in wastewater treatment plants. Chemical and biological treatments were applied to disintegrate excess sludge. At the first step, to enhance biological disintegration, the sludge was pretreated with alkali. At the second step, the sludge was disintegrated by biological treatment. Many kinds of sludge degrading microorganisms integrated the sludge. The efficiency of the new sludge disintegration system was confirmed in a full-scale experiment. The JFE-SD system reduced excess sludge production by approximately 50% during the experimental period. The quality of effluent was kept at quite a good level. Economic analysis revealed that this system could significantly decrease the excess sludge treatment cost.     

Influence of physico-chemical treatment on the subsequent biological process treating paper industry wastewater

The present paper presents the main results of the biodegradation study of paper industry wastewater through physico-chemical treatment. Indeed, around 60% of chemical oxygen demand (COD) removal can be achieved by electroflocculation treatment. Furthermore, a removal efficiency of the COD of almost 91% has been obtained by biological treatment, with activated amount of sludge for 24 h of culture. Concerning the physico-chemical pre-treatment of the untreated, filtered and electroflocculated rejection effluents, it has been investigated through the degradation curve of COD studies.     

Molecular microbial ecology of nitrification in an activated sludge process treating refinery wastewater

The diversity of autotrophic ammonia-oxidizing bacteria (AOB) of the b-subdivision of the class Proteobacteria was investigated in a laboratory-scale denitrification-nitrification bioreactor (DNB) treating a synthetic waste stream. 16S ribosomal RNA (rRNA) gene sequences were amplified from DNA extracted from the oxic DNB sludge. Comparative analysis of the rRNA sequences revealed considerable diversity among the AOB-like sequences. The majority of sequences recovered were related to Nitrosomonas spp. but a smaller number of Nitrosospira-like sequences were obtained. Since different AOB may have different kinetic properties the high diversity of AOB, even in a simple laboratory biotreater treating a simple waste stream, has important implications for the operation of nitrifying wastewater treatment processes.     

Use of electrochemical oxidation process as post-treatment for the effluents of a UASB reactor treating cellulose pulp mill wastewater.

The main purpose of this study was to evaluate the performance of the electrochemical oxidation process as a post-treatment for the effluents of a bench-scale UASB reactor treating simulated wastewater from an unbleached pulp plant. The oxidation process was performed using a single compartment cell with two plates as electrodes. The anode was made of Ti/Ru0.3Ti0.7O2 and the cathode of stainless steel. The following variables were evaluated: current density (75, 150 and 225 mA cm(-2)) and recirculation flow rate in the electrochemical cell (0.22, 0.45 and 0.90 L h(-1)). The increase in current density from 75 to 225 mA cm(-2) did not increased the color removal efficiency for the tested flow rates, 0.22, 0.45 and 0.90 L h(-1), however the energy consumption increased significantly. The results indicated the technical feasibility of the electrochemical treatment as post-treatment for UASB reactors treating wastewaters from pulp and paper plants.