Molecular weight distribution of Pinus radiata kraft mill wastewater treated by anaerobic digestion

Kraft mill is responsible for massive discharge of highly polluted effluents. The main characteristics of this effluent are high toxicity and low biodegradability due to tannin, lignin and chlorophenol compounds. The composition may vary dramatically depending, for instance, on the utilised feedstock and process. The purpose of this work was to investigate the molecular weight distribution of Pinus radiata kraft pulping wastewater treated by anaerobic digestion by using two types of anaerobic reactors: fixed bed and sludge blanket. Anaerobic sludge blanket (UASB) and anaerobic filter (AF) were operated. In both reactors, the total alkalinity ranged between 1.0 and 1.5 g CaCO3/l, while the organic load rate (OLR) was increasing during operation from 1.2 to 3.3 gCOD/l d. COD and total phenolic compounds (UV215) removal ranged between 30-50% and 13-20%, respectively, while the BOD5 removal ranged 60-90%. However only a partial biodegradation (10-43%) of tannin and lignin was observed. Results from ultrafiltration analyses indicated that the fraction with a molecular weight (MW) < 1000, COD and colour decreased after anaerobic treatment, but the total phenolic compounds increased. In the 1000 < MW < 10,000 fraction, there was no change in COD, UV215 and colour. In the > 10,000 MW fraction, colour and COD fraction increased by 14% and 5%, respectively, after anaerobic treatment. It can be concluded from this study, that treatment with UASB or AF reactors is not enough, under the conditions tested, for a large COD removal from Pinus radiata wastewater.     

Continuous anaerobic treatment of wastewater from a kraft pulp mill

A pilot-scale study of the thermophilic anaerobic digestion of high-strength wastewater (evaporator condensate, EC) discharged from a kraft pulp production process was performed. The system consisted of a microfiltration (MF) membrane module for oily substances removal, a stripping system using evolved gas from the digester for sulfur compounds removal, an anaerobic fixed-bed bioreactor for methane fermentation, and an ultrafiltration (UF) membrane module for retention of a high density of bacterial cells. The bioreactor had a fixed-bed with an effective volume of 5 m³ packed with pumice stone. In a continuous run with only the MF membrane module for oily substances removal, the digester efficiency declined because of methanogenic inhibition by sulfur compounds. After fitting of the stripping system which used evolved gas from the digester, the inhibitive sulfur compounds in the EC were removed more than 80%, and high-loading and high-efficiency operation could be attained. The BOD loading and BOD removal of 35.5 kg BOD/m³/d and 93%, respectively were attained. By anaerobic treatment of the evaporator condensate waste before the conventional aerobic activated sludge method, the total costs would be reduced to ¥3.31/m³ wastewater compared with ¥4.53/m³-wastewater by the aerobic activated sludge method only. The stability of digester performance against interruption by feed stoppage was also examined.     

Production of polyhydroxyalkanoates by activated sludge treating a paper mill wastewater

Production of polyhydroxyalkanoates (PHAs) in activated sludge treating wastewater represents an economical and environmental promising alternative to pure culture fermentations. A process for production of PHA from a paper mill wastewater was examined at laboratory scale. The three stage process examined consisted of acidogenic fermentation to convert wastewater organic matter to volatile fatty acids (VFAs), an activated sludge system operating under feast/famine conditions to enrich for PHA producing organisms and accumulation of PHA in batch experiments. After fermentation of the wastewater, 74% of the soluble COD was present as VFA (acetate, propionate, butyrate and valerate) and the resulting PHA after batch accumulation consisted of 31-47 mol% hydroxybutyrate and 53-69 mol% hydroxyvalerate. The maximum PHA content achieved was 48% of the sludge dry weight and the three stage process exhibited a potential to produce 0.11 kg of PHA per kg of influent COD treated.     

Modeling of activated sludge wastewater treatment processes

The performance of an activated sludge wastewater treatment process consisting of an aeration tank and a secondary settler has been studied. A tanks-in-series model with backflow was used for mathematical modeling of the activated sludge wastewater treatment process. Non-linear algebraic equations obtained from the material balances of MLSS (mixed liquor suspended solids or activated sludge), BOD (biological oxygen demand) and DO (dissolved oxygen) for the aeration tank and the settler and from the behavior of the settler were solved simultaneously using the modified Newton-Raphson technique. The concentration profiles of MLSS, BOD and DO in the aeration tank were obtained. The simulation results were examined from the viewpoints of mixing in the aeration tank and flow in the secondary settling tank. The relationships between the overall performance of the activated sludge process and the operating and design parameters such as hydraulic residence time, influent BOD, recycle ratio and waste sludge ratio were obtained.     

Effect of bioaugmentation of activated sludge with white-rot fungi on olive mill wastewater detoxification

AIMS: To test the potential use of Phanerochaete chrysosporium and other white-rot fungi to detoxify olive mill wastewaters (OMW) in the presence of a complex activated sludge. To combine the aerobic with anaerobic treatment to optimize the conversion of OMW in biogas. METHODS AND RESULTS: A 25-l air lift reactor was used to pretreat OMW by white-rot fungi. Detoxification of the OMW was monitored by size exclusion HPLC analysis, chemical oxygen demand (COD)/biological oxygen demand (BOD(5)) ratio evolution, and bioluminescence toxicity test. Anaerobic treatment of OMW was performed in a 12-l anaerobic filter reactor. Efficiency of the treatment was evaluated by organic matter removal, and biogas production. By comparison with the pretreatment by activated sludge only, the bioaugmentation with Phanerochaete chrysosporium or Trametes versicolor led to high removal of organic matter, decreased the COD/BOD(5) ratio and the toxicity. The subsequent anaerobic digestion of the OMW pretreated with activated sludge-white-rot fungi showed higher biomethanization yields than that pretreated with activated sludge only. Higher loading rates (7 g COD l(-1) day(-1)) were reached without any acidification or inhibition of biomethanization. CONCLUSIONS: The use of white-rot fungi, even in the presence of complex biological consortia to detoxify OMW, proved to be possible and made the anaerobic digestion of OMW for methane production feasible. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of fungi for OMW reuse and energy production could be adapted to industrial applications.     

Composting of pulp and paper mill fly ash with wastewater treatment sludge

Wastewater treatment sludge and power boiler fly ash were combined and composted in mixed and static windrows 50 m long, 4 m high and 6 m wide. Moisture content was maintained above 50%. The final compost had a pH of 8.5, contained high concentrations of specific nutrients, and an average C:N ratio of 43:1. All metal, PCB, chlorophenol and PAH concentrations were below levels stipulated by local regulations. Over the first 8 weeks of the composting period dioxin concentration decreased by 45% to 41 pg/g TEQ. Leachate tests indicated minimal (<0.1 mg/l Cu and Pb; <50 mg/l Na, P, and SO₄⁻²) leaching of contaminants from the composted material. Application of compost (8 cubic yards/acre) at a sod farm improved soil characteristics as measured by a number of parameters. The dioxin concentration in the final soil/compost mixture was 3 pg/g TEQ, allowing the soil/compost mixture to be classified as agricultural soil. It was concluded that composting produced an acceptable soil conditioner attractive for large volume users of inexpensive soil material (sod farms, golf courses, land reclamation sites).     

Metaproteomics provides functional insight into activated sludge wastewater treatment

Background

Through identification of highly expressed proteins from a mixed culture activated sludge system this study provides functional evidence of microbial transformations important for enhanced biological phosphorus removal (EBPR).

Methodology/Principal Findings

A laboratory-scale sequencing batch reactor was successfully operated for different levels of EBPR, removing around 25, 40 and 55 mg/l P. The microbial communities were dominated by the uncultured polyphosphate-accumulating organism “Candidatus Accumulibacter phosphatis”. When EBPR failed, the sludge was dominated by tetrad-forming α-Proteobacteria. Representative and reproducible 2D gel protein separations were obtained for all sludge samples. 638 protein spots were matched across gels generated from the phosphate removing sludges. 111 of these were excised and 46 proteins were identified using recently available sludge metagenomic sequences. Many of these closely match proteins from “Candidatus Accumulibacter phosphatis” and could be directly linked to the EBPR process. They included enzymes involved in energy generation, polyhydroxyalkanoate synthesis, glycolysis, gluconeogenesis, glycogen synthesis, glyoxylate/TCA cycle, fatty acid β oxidation, fatty acid synthesis and phosphate transport. Several proteins involved in cellular stress response were detected.

Conclusions/Significance

Importantly, this study provides direct evidence linking the metabolic activities of “Accumulibacter” to the chemical transformations observed in EBPR. Finally, the results are discussed in relation to current EBPR metabolic models.     

Nitrification, denitrification, and dechlorination in bleached kraft pulp mill wastewater

This study deals with combining the biologi cal removal of organic halogens with the removal of nitrogen from bleached kraft pulp mill wastewater in fluidized-bed reactors under nitrifying and denitrifying conditions. Untreated and biotreated bleached kraft pulp mill wastewaters had no detrimental effect on nitrification or denitrification. The nitrifying biofilm reactor, pregrown on synthetic inorganic feed with ammonia, removed without a lag phase adsorbable organic halogens [7.2 mg Cl (g biomass volatile solids)⁻¹day⁻¹] from bleached kraft pulp mill wastewater and selected chlorophenols from synthetic wastewater. Electron microscopical examination of the biofilm showed that bacteria, morphologically similar to the nitrifying species Nitrosomonas or Nitrobacter, and Nitrosospira were dominant. The denitrifying fluidized-bed reactor, pregrown on nitrate and methanol, denitrified without a lag phase bleached kraft pulp mill wastewater. Under denitrifying conditions, 35% of the total organic carbon content of untreated bleached kraft pulp mill waste water was removed. The reducing power delivered by untreated bleached kraft pulp mill wastewater for denitrification was 2 mmol electrons/mmol carbon mineralized. Dechlorination under denitrifying conditions was negligible. Received: 21 November 1996 / Received revision: 27 January 1997 / Accepted: 1 February 1997     

Microbial composition of the activated sludge of Moscow wastewater treatment plants

The contribution of the major technologically important microbial groups (ammonium- and nitrite-oxidizing, phosphate-accumulating, foam-inducing, and anammox bacteria, as well as planctomycetes and methanogenic archaea) was characterized for the aeration tanks of the Moscow wastewater treatment facilities. FISH investigation revealed that aerobic sludge were eubacterial communities; the metabolically active archaea contributed insignificantly. Stage II nitrifying microorganisms and planctomycetes were significant constituents of the bacterial component of activated sludges, with Nitrobacter spp. being the dominant nitrifiers. No metabolically active anammox bacteria were revealed in the sludge from aeration tanks. The sludge from the aeration tanks using different wastewater treatment technologies were found to have differing characteristics. Abundance of the nitrifying and phosphate-accumulating bacteria in the sludge generally correlated with microbial activity in microcosms and with efficiency of nitrogen and phosphorus removal from wastewater. The highest microbial numbers and activity were found in the sludge of the tanks operating according to the technologies developed in the universities of Hannover and Cape Town. The activated sludge from the Novokur’yanovo facilities, where abundant growth of filamentous bacteria resulted in foam formation, exhibited the lowest activity. The group of foaming bacteria included Gordonia spp. and Acinetobacter spp utilizing petroleum and motor oils, Sphaerotilus spp. utilizing unsaturated fatty acids, and Candidatus ‘Microthrix parvicella’. Thus, the data on abundance and composition of metabolically active microorganisms obtained by FISH may be used for the technological control of wastewater treatment.     

Diversity and dynamics of Archaea in an activated sludge wastewater treatment plant

ABSTRACT: BACKGROUND: The activated sludge process is one of the most widely used methods for treatment of wastewater and the microbial community composition in the sludge is important for the process operation. While the bacterial communities have been characterized in various activated sludge systems little is known about archaeal communities in activated sludge. The diversity and dynamics of the Archaea community in a full-scale activated sludge wastewater treatment plant were investigated by fluorescence in situ hybridization, terminal restriction fragment length polymorphism analysis and cloning and sequencing of 16S rRNA genes. RESULTS: The Archaea community was specialized and dominated by Methanosaeta-like species. During a 15 month period major changes in the community composition were only observed twice despite seasonal variations in environmental and operating conditions. Water temperature appeared to be the process parameter that affected the community composition the most. Several terminal restriction fragments also showed strong correlations with sludge properties and effluent water properties. The Archaea were estimated to make up 1.6-% of total cell numbers in the activated sludge and were present both as single cells and colonies of varying sizes. CONCLUSIONS: The results presented here show that Archaea can constitute a constant and integral part of the activated sludge and that it can therefore be useful to include Archaea in future studies of microbial communities in activated sludge.     

Occurrence and activity of Archaea in aerated activated sludge wastewater treatment plants

The occurrence, distribution and activity of archaeal populations within two aerated, activated sludge wastewater treatment systems, one treating domestic waste and the second treating mixed domestic and industrial wastewater, were investigated by denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified ribosomal RNA gene fragments and process measurements. In the plant receiving mixed industrial and domestic waste the archaeal populations found in the mixed liquor were very similar to those in the influent sewage, though a small number of DGGE bands specific to the mixed liquor were identified. In contrast, the activated sludge treating principally domestic waste harboured distinct archaeal populations associated with the mixed liquor that were not prevalent in the influent sewage. We deduce that the Archaea in the plant treating mixed wastewater were derived principally from the influent, whereas those in the plant treating solely domestic waste were actively growing in the treatment plant. Archaeal 16S rRNA gene sequences related to the Methanosarcinales, Methanomicrobiales and the Methanobacteriales were detected. Methanogenesis was measured in activated sludge samples incubated under oxic and anoxic conditions, demonstrating that the methanogens present in both activated sludge plants were active only in anoxic incubations. The relatively low rates of methanogenesis measured indicated that, although active, the methanogens play a minor role in carbon turnover in activated sludge.     

Characteristics of PAHs adsorption on inorganic particles and activated sludge in domestic wastewater treatment

The occurrence of polycyclic aromatic hydrocarbons (PAHs) in a domestic wastewater treatment plant (WWTP) was investigated in a 1 year period. In order to understand how PAHs were removed at different stages of the treatment process, adsorption experiments were conducted using quartz sand, kaolinite, and natural clay as inorganic adsorbents and activated sludge as organic adsorbent for adsorbing naphthalene, phenanthrene, and pyrene. As a result, the adsorption of PAHs by the inorganic adsorbents well followed the Langmuir isotherm while that by the activated sludge well followed the Freundlich isotherm. By bridging equilibrium partitioning coefficient with the parameters of adsorption isotherm, a set of mathematical models were developed. Under an assumption that in the primary settler PAHs removal was by adsorption onto inorganic particles and in the biological treatment unit it was by adsorption onto activated sludge, the model calculation results fairly reflected the practical condition in the WWTP.     

Enhanced nutrient removal of immobilized activated sludge system

Summary Immobilized activated sludge system with porous polyurethane foam pads was operated in time-sequenced anoxic/oxic batch mode for the enhanced nutrient removal. Biomass hold-up in polyurethane foam pads in immobilized sytem increased with incoming organic substrate concentration. This new trouble-free system showed improved capability in nitrogen and phosphorus removal than conventional activated sludge system.     

肇庆市某污水厂CASS工艺的调试与运行性能

对肇庆市某新建城市污水处理厂进行工艺调试,研究了其CASS系统对进水的处理效果.结果表明,调试阶段,进水COD_Cr、BOD₅、NH₄⁺-N和TP浓度分别为117.3～446.4 mg·L^-1、60.5～225.9 mg·L^-1、7.6～34.3 mg·L^-1和1.85～5.49 mg·L^-1,对应地,出水浓度分别为18.6～63.2 mg·L^-1、8.0～29.2 mg·L^-1、2.0～8.8 mg·L^-1和0.22～0.83 mg·L^-1.正常运行并优化工艺后,出水BOD₅、NH₄⁺-N和TP可达标排放.CASS池微生物数量丰富,正常运行阶段每克干污泥中,细菌、酵母菌和霉菌总数分别高达4.2×10¹⁰±1.8×10¹⁰CFU、2.5×10⁷±1.8×10⁷CFU和3.6×10⁶±2.6×10⁶CFU.     

Configuration of biological wastewater treatment line and influent composition as the main factors driving bacterial community structure of activated sludge

The structure of microbial consortia in wastewater treatment facilities is a resultant of environmental conditions created by the operational parameters of the purification process. In the research, activated sludge from nine Polish wastewater treatment plants (WWTPs) was investigated at a molecular level to determine the impact of the complexity of biological treatment line and the influent composition on the species structure and the diversity of bacterial consortia. The community fingerprints and technological data were subjected to the canonical correspondence and correlation analyses. The number of separated biological processes realized in the treatment line and the presence of industrial wastewater in the influent were the key factors determining the species structure of total and ammonia-oxidizing bacteria in biomass. The N₂O-reducers community composition depended significantly on the design of the facility; the highest species richness of denitrifiers was noted in the WWTPs with separated denitrification tanks. The contribution of industrial streams to the inflow affected the diversity of total and denitrifying bacterial consortia and diminished the diversity of ammonia oxidizers. The obtained data are valuable for engineers since they revealed the main factors, including the design of wastewater treatment plant, influencing the microbial groups critical for the stability of purification processes.     

ERIC-PCR-based strain-specific detection of phenol-degrading bacteria in activated sludge of wastewater treatment systems

Aims:  To evaluate the use of Enterobacterial Repetitive Intergenic Consensus PCR (ERIC-PCR)-derived probes and primers to specifically detect bacterial strains in an activated sludge microbial community.
Methods and Results:  ERIC-PCR was performed on two phenol-degrading bacterial strains, Arthrobacter nicotianae P1-7 and Klebsiella sp. P8-14. Their amplicons were DIG labelled for use as probes and then hybridized with ERIC-PCR fingerprints. The results showed the distinct band patterns for both bacterial strains. Strain-specific PCR primers were designed based on the sequences of ERIC-PCR bands. The DNA of each of these strains was successfully detected from its mixture with activated sludge DNA, either by using their respective ERIC-PCR-based probes for hybridization or by using species-specific primers for amplification, with higher sensitivity by latter method.
Conclusions:  Two phenol-degrading bacterial strains were identified from a mixture of activated sludge by using ERIC-PCR-based methods.
Significance and Impact of the Study:  The study demonstrated that the bacteria, which have important functions in complex wastewater treatment microbial communities, could be specifically detected by using ERIC-PCR fingerprint-based hybridization or amplification.     

城市污水处理厂活性污泥生物泡沫研究进展

城市污水处理厂运行过程中一旦发生活性污泥生物泡沫,就会影响污泥沉降和处理厂运行效能,对出水水质、作业安全和公共健康带来一系列挑战。生物泡沫是自活性污泥法诞生以来长期困扰污水处理厂运行的难题。生物泡沫的形成需要气泡、表面活性物质和疏水物质等3点基本的要素,在其中主要富集了诺卡氏型丝状细菌(Nocardioformfilamentousbacteria)和微丝菌(Candidatus Microthrix parvicella)这两种类型微生物。多种环境和运行因素包括温度、溶解氧、pH、污泥龄、特别是营养物质种类和浓度等均会对这些丝状微生物的生长产生影响。抑制丝状细菌生长的常用控制策略包括选择器、生长动力学控制、投加化学药剂以及噬菌体等方法,通过降低两类丝状细菌在生化池中的浓度以期消除生物泡沫现象。本文总结了生物泡沫的类型、成因、表征生物泡沫程度的指标、影响生物泡沫的环境因素以及常用的调控策略的原理及优缺点等,尽可能全面地介绍活性污泥生物泡沫的研究现状,并探讨未来研究方向和控制策略,期望能够为今后研究活性污泥微生物和污水处理厂运行调控提供有价值的参考。