Bulking in aerobic biological systems treating dairy processing wastewaters

The aerobic biological treatment of dairy processing wastewaters is associated with poor sludge settling bulking, and this has been largely linked to the high soluble organic component in these wastewaters, and high chemical oxygen demand COD: NP ratios. Strategies to minimize sludge bulking in activated sludge systems or sequencing batch reactors have been identified and include the operation of these systems under extended aeration conditions, and the incorporation of an anaerobic or anoxic zone to facilitate the degradation of the readily metabolized lactose in the wastewater. Filamentous bacteria linked with sludge bulking in the industry have been associated with various operating conditions.     

Dimethyl sulfoxide (DMSO) waste residues and municipal waste water odor by dimethyl sulfide (DMS): the north-east WPCP plant of Philadelphia

This study shows for the first time that overlooked mg/L concentrations of industrial dimethyl sulfoxide (DMSO) waste residues in sewage can cause "rotten cabbage" odor problems bydimethyl sulfide (DMS) in conventional municipal wastewater treatment. In laboratory studies, incubation of activated sludge with 1-10 mg/L DMSO in bottles produced dimethyl sulfide (DMS) at concentrations that exceeded the odor threshold by approximately 4 orders of magnitude in the headspace gas. Aeration at a rate of 6 m3 air/m3 sludge resulted in emission of the DMS into the exhaust air in a manner analogous to that of an activated sludge aeration tank. A field study atthe NEWPCP sewage treatment plant in Philadelphia found DMSO levels intermittently peaking as high as 2400 mg/L in sewage near an industrial discharger. After 3 h, the DMSO concentration in the influent to the aeration tank rose from a baseline level of less than 0.01 mg/L to a level of 5.6 mg/L and the DMS concentration in the mixed liquor rose from less than 0.01 to 0.2 mg/L. Finding this link between the intermittent occurrence of DMSO residues in influent of the treatment plant and the odorant DMS in the aeration tank was the keyto understanding and eliminating the intermittent "canned corn" or "rotten cabbage" odor emissions from the aeration tank that had randomly plagued this plant and its city neighborhood for two decades. Sewage authorities should consider having wastewater samples analyzed for DMSO and DMS to check for this possible odor problem and to determine whether DMSO emission thresholds should be established to limit odor generation at sewage treatment plants.     

Effectiveness of aeration and mixing in the remediation of a saline stratified river

This study examines the use of an aeration scheme to remediate low oxygen conditions in a saline stratified system. The Tawe estuary was impounded in 1992 and quickly developed saline stratification during the summer months which led to an anoxic hypolimnon. In 1998 trials began in which a suite of aerators was applied to remediate the water quality; the trial was later extended to a full aeration scheme. This study examines pre-aeration conditions in order to delineate conditions under which poor water quality would develop, and would therefore be the conditions when aeration would be necessary. Furthermore, the study compared identical periods within the impoundment during which the following conditions existed: no aeration; and aeration with first 44, then 88, aerators. The study shows that (i) destratification occurred naturally under flows of >10 m3/s, and no low dissolved oxygen conditions were observed at higher flows; (ii) the presence of all levels of aeration had a statistically significant effect upon dissolved oxygen (DO) levels; the effect of increasing the number of aerators was approximately linear; (iii) the average effect of aeration was an increase of up to 3 mg/L DO in the deepest water; (iv) the frequency of low DO conditions decreased from 19% to 3% with the operation of aerators; and (v) aeration is most effective during periods of no tidal incursion and further from the saline water source. This study is the first to demonstrate the effectiveness of aeration in a saline stratified system.     

Comparison performances of membrane bioreactor and conventional activated sludge prcesses on sludge reduction induced by Oligochaete

Pilot-scale experiments were carried out to compare sludge reduction induced by Oligochaete in a submerged membrane bioreactor (MBR) and a conventional activated sludge (CAS) reactor for 345 d. Worm growth in the CAS reactor was much better than in the MBR. The average worm density of the aeration tank in the CAS reactor was 71 total worms/mg of volatile suspended solids (VSS), much higher than that in the MBR (10 total worms/mg of VSS). Worms did not naturally produce in the MBR, and the dominant worm type in the MBR depended on sludge inoculation from the CAS reactor. Only two types of worms were found in the MBR, Aeolosoma hemprichicii and Nais elinguis. Worm presence and disappearance in the MBR alternated. Worms in the CAS reactor occurred nearly throughout the operating period and were continuously maintained at over 30 total worms/mg of VSS in the aeration tank for 172 d. Three types of worm were found in the CAS reactor, A. hemprichicii, Pristina aequiseta, and N. elinguis, but P. aequiseta was present only occasionally. The alternating dominance of worm types in both reactors changed between Aeolosoma and Nais, and the time of Aeolosoma dominance was longer than that of Nais dominance. Worm growth in the MBR contributed to neither sludge reduction nor improvement of sludge settling characteristics because of low density. But worm presence and bloom in the CAS reactor greatly decreased sludge yield and improved sludge settling characteristics at high density. Both the average sludge yield (0.17 kg of suspended solids (SS)/kg of chemical oxygen demand removed (CODremoved)) and sludge volume index (60 mL/g) in the CAS reactor were much lower than those in the MBR (0.40 kg of SS/kg of CODremoved and 133 mL/g). Nais had more potential for sludge reduction than Aeolosoma. Worm growth had little impact on effluent quality in the MBR but affected effluent quality very much in the CAS reactor.     

Characterization of denitrifying polyphosphate-accumulating organisms in activated sludge based on nitrite reductase gene

Nitrite reductase gene (nirS) fragments in the activated sludge obtained from a sequencing batch reactor (SBR) under anaerobic-aerobic condition were cloned and classified by restriction fragment length polymorphism (RFLP) analysis, and representative fragments were sequenced. One of the nirS clones was approximately 70% of all nirS clones in anaerobic/aerobic (existing oxygen and nitrate) cycle operation in which a large amount of anoxic phosphate uptake was observed. Although the activated sludge samples analyzed might contain bacteria that did not accumulate polyphosphate, it was likely that this nirS fragment sequence was that from denitrifying polyphosphate-accumulating organisms (DNPAOs) which can utilize both oxygen and nitrate as electron acceptors. The sequence was similar to the nirS sequences of Thauera mechernichensis (83% similarity) and Azoarcus tolulyticus (83% similarity) both of which belong to the Rhodocyclus group.     

Influence of different mesh filter module configurations on effluent quality and long-term filtration performance

Recently, a new type of wastewater treatment system became the focus of scientific research: the mesh filter activated sludge system. It is a modification of the membrane bioreactor (MBR), in which a membrane filtration process serves for sludge separation. The main difference is that a mesh filter is used instead of the membrane. The effluent is not of the same excellent quality as with membrane bioreactors due to the much lager pore sizes of the mesh. Nevertheless, it still resembles the quality of currently used standard treatment system, the activated sludge process. The new process shows high future potential as an alternative where a small footprint of these plants is required (3 times lower footprint than conventional activated sludge systems because of neglecting the secondary clarifier and reducing the biological stage). However, so far only limited information on this innovative process is available. In this study, the effect of different pore sizes and different mesh module configurations on the effluent quality was investigated varying the parameters cross-flow velocity (CFV) and flux rate. Furthermore the long-term filtration performance was studied in a pilot reactor system and results were compared to the full-scale conventional activated sludge process established at the same site. The results demonstrate that the configuration of the filter module has little impact on effluent quality and is only of importance with regard to engineering aspects. Most important for a successful operation are the hydrodynamic conditions within the filter module. The statement "the higher the pore size the higher the effluent turbidity" was verified. Excellent effluent quality with suspended solids between 5 and 15 mg L(-1) and high biological elimination rates (chemical oxygen demand (COD) 90-95%, biological oxygen demand (BOD5) 94-98%, total nitrogen (TN) 70-80%, and ammonium nitrogen (NH(4)-N) 95-99%) were achieved and also compared to those of conventional activated sludge systems. Regarding the air requirement for module aeration, which is the main cost factor in MBR technology, an astonishing optimization could be achieved. During the long-term filtration experiments only 4 N m(3)/m(3) was necessary to keep a stable filtration process for more than 3 weeks (MBR 20-50 N m(3)/m(3)).     

Treatment of wastewater from a whey processing plant using activated sludge and anaerobic processes

Wastewater from a whey processing plant was treated in two on-site pilot plants, a three-stage activated sludge plant and an anaerobic reactor, each of which had the capacity of treating 230 L/h of wastewater. The activated sludge treatment was very effective. It reduced 99% of 5-d biochemical oxygen demand of the plant wastewater (from an average of 1062 to 9 mg/L) and 91% of total Kjeldahl nitrogen (from 109 to 10 mg/L) after a total retention time of 19.8 h. The intermediate 5-d biochemical oxygen demand reductions were 86% after 3.8 h in the first stage and 97% after another 8 h in the second stage. The completely mixed anaerobic reactor reduced only 87% of 5-d biochemical oxygen demand after 2 d of retention. However, with an additional 8 h of activated sludge treatment the total 5-d biochemical oxygen demand was reduced by 99%. Both pilot plants were operated smoothly in spite of the considerable fluctuations in pollutant levels of the plant wastewater.     

Relationship between solid retention time and phosphorus removal in anaerobic-intermittent aeration process

Solid retention time (SRT) is one of the most important control parameters in biological phosphorus removal. In this study, lab-scale biological nutrient removal (BNR) reactors using anaerobic-intermittent aeration (AIA) were operated at various SRTs (i.e., 15, 20, and 30 d) to evaluate their phosphorus removal efficiencies. Sludge wasting load decreased as SRT increased; however, the phosphorus content in the biomass increased as SRT increased. The highest phosphorus removal efficiency was 93% at an SRT of 20 d and the phosphorus wasting load was also highest at that SRT, which indicates that the optimal SRT for the highest phosphorus removal is not proportional to the phosphorus content in the biomass. Aerobic digestion experiments were also carried out to determine the number of phosphate-accumulating organisms (PAOs) in the biomass produced in different reactors. All three activated sludges from BNR at SRTs of 15, 20, and 30 d showed a slower volatile suspended solid (VSS) destruction rate and a larger amount of phosphorus released than the conventional activated sludge (CAS), suggesting that the activated sludge from BNR has more PAOs than CAS. Also, the sludge at an SRT of 30 d showed a slower VSS destruction rate and a larger amount of phosphorus released than the sludge at an SRT of 15 d, suggesting that PAOs are more predominant at longer SRTs. Thus, to improve phosphorus removal efficiency, it is recommended that SRT be increased to maximize the number of PAOs in the system and that SRT be determined to maximize phosphorus wasting load.     

SBR法对缫丝废水的后续处理试验研究

通过研究影响序批式活性污泥法(SBR法)对缫丝废水的后续处理效果的各种因素,得出最佳工况运行条件。结果表明,在SBR法中,曝气时间为8 h,沉淀时间为40 min,溶解氧值为2～3 mg/L时,系统处理效果最好,COD、氨氮和TP的去除率分别达到90.5%±0.5%、95.1%±0.6%和78.2%±3.1%,出水的COD和氨氮都能达标排放。将SBR反应器作为缫丝废水后续好氧处理工艺,具有较高的处理效率和较好的运行稳定性。     

The effect of aeration on the development of mite populations in rapeseed

The development of the mite infestation in 10–12 tonne bulks of rapeseed was studied in two consecutive tests. In the first, lasting 20 months, a comparison was made of populations in seed at 8% moisture content in an aerated, an unaerated and a hermetically sealed bin. In the second, the numbers of mites which developed during 9 months storage was compared for two unaerated and two aerated bins of seed near 9% moisture content.

In seed at 8% moisture content Glycyphagus spp. and Cheyletus spp. were the commonest mites. No mites were found in the aerated bin in the 6 months before the spring when aeration was halted because the temperatures of the air and the seed began to rise above 5 C. In 10 months the mean number of mites in this bin reached nearly 600/kg but meanwhile in the unaerated and the sealed bins the number of mites had reached nearly 4000/kg. Mite populations slowly declined in all bins thereafter.

In seed at 9% moisture content Acarus spp. were the commonest mites. The final mean infestation in the unaerated bins exceeded 36,000/kg but in the two aerated bins, where the temperature of the seed was kept below 5°C for 4 months and where the seed dried by at least 0.5% the final mean infestation remained below 2000/kg.     

Biodegradation of p-nitrophenol by aerobic granules in a sequencing batch reactor

In this study, aerobic granules to treat wastewater containing p-nitrophenol (PNP) were successfully developed in a sequencing batch reactor (SBR) using activated sludge as inoculum. A key step was the conditioning of the activated sludge seed to enrich for biomass with improved settleability and higher PNP degradation activity by implementing progressive decreases in settling time and stepwise increases in PNP concentration. The aerobic granules were cultivated at a PNP loading rate of 0.6 kg/ m3 x day, with glucose to boost the growth of PNP-degrading biomass. The granules had a clearly defined shape and appearance, settled significantly faster than activated sludge, and were capable of nearly complete PNP removal. The granules had specific PNP degradation rates that increased with PNP concentration from 0 to 40.1 mg of PNP/L, peaked at 19.3 mg of PNP/(g of VSS) x h (VSS = volatile suspended solids), and declined with further increases in PNP concentration as substrate inhibition effects became significant. Batch incubation experiments show that the PNP-degrading granules could also degrade other phenolic compounds, such as hydroquinone, p-nitrocatechol, phenol, 2,4-dichlorophenol, and 2,6-dichlorophenol. The PNP-degrading granules contained diverse microbial morphotypes, and PNP-degrading bacteria accounted for 49% of the total culturable heterotrophic bacteria. Denaturing gradient gel electrophoresis analysis of 16S rRNA gene fragments showed a gradual temporal shift in microbial community succession as the granules developed from the activated sludge seed. Specific oxygen utilization rates at 100 mg/L PNP were found to increase with the evolution of smaller granules to large granules, suggesting that the granulation process can enhance metabolic efficiency toward biodegradation of PNP. The results in this study demonstrate that it is possible to use aerobic granules for PNP biodegradation and broadens the benefits of using the SBR to target treatment of toxic and recalcitrant organic compounds.     

CQJ型气浮技术在思茅松制浆废水处理中的应用

介绍云景林纸废水处理工艺“物理化学处理法＋好氧生物处理法＋化学处理法”的原理,以及CQJ型超效浅层气浮在处理思茅松制浆废水中的应用及特点。     

Bactericidal effects of wine on Vibrio parahaemolyticus in oysters

The bactericidal effects of wines on Vibrio parahaemolyticus in oysters were studied to evaluate potential inactivation of V. parahaemolyticus in contaminated oysters by wine consumption. Shucked whole oyster and oyster meat homogenate were inoculated with V. parahaemolyticus and mixed with red or white wine. Survivals of V. parahaemolyticus in inoculated oysters were determined at 7 and 25 degrees C. Populations of V. parahaemolyticus in inoculated whole oysters (5.52 log most probable number [MPN] per g) decreased slightly to 4.90 log MPN/g (a 0.62-log reduction) after 24 h at 7 degrees C but increased to 7.37 log MPN/g over the same period at 25 degrees C. However, the populations in wine-treated whole oysters decreased by >1.7 and >1.9 log MPN/g after 24 h at 7 and 25 degrees C, respectively. Both red and white wines were more effective in inactivating V. parahaemolyticus in oyster meat homogenate than in whole oyster. Populations of V. parahaemolyticus in oyster meat homogenate (7.8 x 10(3) MPN/g) decreased rapidly to nondetectable levels (< 3 MPN/g) after 30 min of mixing with wine at 25 degrees C (a 3.89-log MPN/g reduction). These results suggest that chewing oysters before swallowing when eating raw oysters may result in greater inactivation of V. parahaemolyticus if wine is consumed. More studies are needed to determine the bactericidal effects of wine on V. parahaemolyticus in the complicated stomach environment.     

Recovery of Escherichia coli Biotype I and Enterococcus spp. during refrigerated storage of beef carcasses inoculated with a fecal slurry.

Three beef front quarters/carcasses were inoculated with a slurry of cattle manure. During storage at 4 degrees C, two sponge samples from each of three sites (i.e., 100 cm2 from each of two fat surfaces and 100 cm2 from a lean surface) were taken from each of the three carcasses on days 0, 1, 3, 7, and 10 after inoculation. The initial numbers of Escherichia coli averaged 2.0 log10 CFU/cm2 (1.21 to 2.47 log10 CFU/cm2) using the Petrifilm method and 2.09 log10 most probable number (MPN)/cm2 (0.88 to 2.96 log10 MPN/cm2) using the MPN method. The initial numbers of enterococci averaged 3.34 log10 CFU/cm2 (3.07 to 3.79 log10 CFU/cm2) using kanamycin esculin azide agar. In general, an appreciable reduction in the numbers of E. coli occurred during the first 24 h of storage; for the Petrifilm method an average reduction of 1.37 log10 CFU/cm2 (0.69 to 1.71 log10 CFU/cm2) was observed, and for the MPN method an average reduction of 1.52 log10 MPN/cm2 (0.47 to 2.08 log10 MPN/cm2) was observed. E. coli were not detected (<-0.12 log10 CFU/cm2) using Petrifilm on day 7 of the storage period on two (initial counts of 1.21 and 2.29 log10 CFU/cm2) of the three carcasses. However, viable E. coli cells were recovered from these two carcasses after a 24-h enrichment at 37 degrees C in EC broth. Viable E. coli cells were detected at levels of -0.10 log10 CFU/cm2 on the third carcass (initial count of 2.47 log10 CFU/cm2) after 7 days at 4 degrees C. No significant difference in recovery of viable cells was observed between the MPN and Petrifilm methods on days 0, 1, and 3 (P > 0.05). However, viable E. coli cells were recovered from all three carcasses by the MPN method on day 7 at an average of -0.29 log10 MPN/ cm2 (-0.6 to -0.1 log10 MPN/cm2). On day 10, viable cells were recovered by the MPN method from two of the three carcasses at -0.63 and -0.48 log10 MPN/cm2 but were not recovered from the remaining carcass (<-0.8 log10 MPN/cm2). Similar to E. coli, the greatest reduction (average of 1.26 log10 CFU/cm2, range = 1.06 to 1.45 log10 CFU/cm2) in the numbers of enterococci occurred during the first 24 h of storage. Because of higher initial numbers and a slightly slower rate of decrease, the numbers of Enterococcus spp. were significantly higher (P < 0.017) than the numbers of E. coli Biotype I after 3, 7, and 10 days of storage. These results suggest that enterococci may be useful as an indicator of fecal contamination of beef carcasses.     

The effects of intermittent aeration on the characteristics of bio-cake layers in a membrane bioreactor

The effects of a sequencing variation for dissolved oxygen (DO) concentrations on the membrane permeability in a submerged membrane bioreactor (MBR) were studied. An MBR was continuously operated under alternating DO conditions, e.g., 36 h of an aerobic phase, followed by 36 h of an anoxic phase. The rate of increase in transmembrane pressure (TMP) in the anoxic phase was always steeper than that in the aerobic phase, indicating that the fouling rate was higher in the anoxic than in the aerobic condition. Regardless of the phases, the rate of TMP increase became steeper as the cycles were repeated. However, this trend became less important as the cycle numbers increased. Even in identical microbial communities, the number of colloidal particles and soluble extracellular polymeric substances (EPS) in the bulk solution were increased during the anoxic condition, which caused a reduction in the porosity of the bio-cake. During analysis of the bio-cake profile along the cake depth, the temporal variation of the bio-cake structure was attributed to the temporal change in the number of colloidal particles as well as the change in compression forces acting on the bio-cake. The influence of the latter was found to be more important than that of the former, which was verified by comparing the various structures of bio-cake formed in differing DO environments.     

陕西省某活鸡屠宰场肉鸡相关样品中沙门菌定量检测及污染分析

目的了解肉鸡屠宰加工中不同时间和环节沙门菌的污染情况,分析污染关键点。方法 2016年11月至2017年11月从陕西省某活鸡屠宰场不同环节定期采集活鸡肛拭子标本、整鸡胴体和鸡肉样品,使用最大可能数(MPN)法对沙门菌进行定量检测,同时分离菌株;采用聚合酶链式反应(PCR)技术对沙门菌进行鉴定,同时结合血清凝集技术对沙门菌鉴定结果进行确认。结果采集的284份样品中有67份检出沙门菌,检出率为23. 6%,平均MPN值为0. 051 6 MPN/g。2017年7月采集的样品沙门菌污染最为严重,检出率为37. 8%(14/37),平均MPN值为0. 064 7 MPN/g; 2016年11月检出率最低,为13. 9%(5/36),平均MPN值为0. 043 6 MPN/g。不同屠宰环节中,浸烫褪毛后整鸡胴体样品中沙门菌检出率最高(43. 3%,26/60),平均MPN值为0. 060 5 MPN/g;分割后冷冻前鸡胸脯肉样品中沙门菌检出率最低(18. 3%,11/60),平均MPN值为0. 036 8 MPN/g,略高于储存配送过程整鸡胴体/鸡胸脯肉样品中沙门菌的污染水平(0. 035 8 MPN/g)。结论活鸡屠宰过程沙门菌的检出率与MPN值具有较强的季节性,在不同屠宰加工环节存在纵向和交叉污染,应对活鸡屠宰加工过程沙门菌污染严重的环节进行重点控制。     

造纸厂废水处理系统故障的解决实例

甘肃某造纸企业采用改良式氧化沟工艺及射流曝气系统处理中段废水,由于产能扩建、生产不稳定等原因造成浅层气浮加药量不易控制、曝气池产生大量泡沫、二沉池出现漂泥现象等一系列问题,通过加大初期排泥、增加溶解氧供应、减少回流污泥等措施,取得了满意的效果。     

Enzymic Extraction of Native Starch from Sago (Metroxylon sagu) Waste Residue

Residual native starch was extracted from sago pith residue using two types of commercial cell‐wall degrading enzymes, Pectinex Ultra SP‐L and Ultrazyme 100G. The first increased starch yield with a shorter incubation period than the second. The superior effect of Pectinex Ultra SP‐L was observed already at 0.5 h, where a wide granule size distribution (8—87 μm) was obtained. A slight increase in the release of granules ranging from 30—60 μm was noted within a 2 h incubation period. However, upon further incubation, the distribution pattern was similar to that of untreated samples. Samples treated with Ultrazyme 100G exhibited a unimodal distribution pattern, with larger granules, ranging from 40—70 μm, being released upon further incubation within a 2 h incubation period. However, all samples exhibited a bimodal distribution upon further incubation.     

pH及溶氧对重组大肠杆菌发酵生产5-氨基乙酰丙酸的影响

以重组大肠杆菌DALA为实验菌株,研究了该菌株在机械搅拌通风发酵罐发酵过程中pH以及溶解氧对5-氨基乙酰丙酸（ALA）积累的影响。结果发现,发酵前期（0～27 h）pH保持为6.5;稳定期后期（28～48 h）,pH为6.0时有利于5-ALA的积累。其次,通过控制转速与通气量调节发酵液中的溶氧,发现发酵前期转速为500 r/min,通气量为2 vvm;稳定期后期,转速降低至250 r/min,通气量减少为1 vvm,有利于重组菌DALA发酵生产5-ALA,在此条件下发酵5-ALA的产量可达到3.46 g/L。     

Potential of predominant activated sludge bacteria as recipients in conjugative plasmid transfer

We investigated the possibility of conjugative plasmid transfer to the predominant bacteria in activated sludge and the factors influencing the transfer frequency in the activated sludge process. We performed conjugative transfers of a self-transmissible, broad-host-range plasmid RP4 from Escherichia coli C600 to activated sludge bacteria by broth mating. Most of the activated sludge bacteria tested could acquire plasmid RP4, although the transfer frequencies varied from 8.8 x 10(-7) to 1.3 x 10(-2) transconjugants per recipient. The transfer frequencies in several strains were similar to, or higher than, that in intraspecific transfer to E. coli HB101. Matings under various environmental conditions showed that factors relevant to physiological activity, such as temperature and nutrient conditions, seemed to affect the transfer frequency. In addition, conjugative transfer was detected even in filtered raw and treated wastewaters. Thus, the predominant activated sludge bacteria seem to have sufficient potential as recipients in conjugative plasmid transfer under the conditions likely to occur in the activated sludge process. Transfer frequency was reduced by agitation in the presence of suspended solid. This may suggest that conjugative plasmid transfer is physically inhibited in aeration tanks.