低强强度超声波强化膨胀污泥好氧消化

污泥膨胀是城市污水处理厂经常遇到的棘手问题.试验采用低强度超声波对膨胀污泥的好氧消化过程进行强化,选取超声强度、超声时间、超声间隔三个因素设计正交试验.对试验结果的极差分析和方差分析表明,低强度超声波强化膨胀污泥好氧消化的最佳参数为:超声强度0.2 W/cm2、超声时间5 min、超声间隔8 h.试验中经超声辐照的膨胀污泥,其好氧消化达标最短仅需6.73 d,比未加超声的对照试验提前了5.34 d.试验还研究了膨胀污泥达标前后溶解性化学需氧量(SCOD)和总化学需氧量(TCOD)的变化情况.结果表明,达标时污泥的SCOD变化不大,而TCOD较对照得到了不同程度的降低,最大达到76.1%,污泥的稳定性得到不同程度的提高.     

低强度超声波强化膨胀污泥好氧消化

污泥膨胀是城市污水处理厂经常遇到的棘手问题。试验采用低强度超声波对膨胀污泥的好氧消化过程进行强化,选取超声强度、超声时间、超声间隔三个因素设计正交试验。对试验结果的极差分析和方差分析表明,低强度超声波强化膨胀污泥好氧消化的最佳参数为:超声强度0.2W/cm~2、超声时间5min、超声间隔8h。试验中经超声辐照的膨胀污泥,其好氧消化达标最短仅需6.73d,比未加超声的对照试验提前了5.34d。试验还研究了膨胀污泥达标前后溶解性化学需氧量(SCOD)和总化学需氧量(TCOD)的变化情况。结果表明,达标时污泥的SCOD变化不大,而TCOD较对照得到了不同程度的降低,最大达到76.1%,污泥的稳定性得到不同程度的提高。     

超声波强化活性污泥活性的试验研究

研究了超声波对活性污泥活性的影响,用污泥好氧速率OUR来衡量活性,并通过模拟人工废水试验验证。研究表明超声波频率为25kHz,输出声密度为0·2W/mL,作用60s后,污泥活性比原污泥提高30.49%;相同条件超声3s后,污泥活性比原污泥提高20%。试验中从能耗角度推荐选用超声3s。脉冲方式比连续超声更能改善污泥活性,且脉冲比1∶1时效果最好。超声3s后的活性污泥处理人工废水的出水水质明显好于未经处理的出水水质。     

低强度超声提高污泥活性的运行条件优化

为优化超声处理提高污泥活性的运行条件,考察了超声波的频率、强度、作用时间和污泥浓度等因素的影响.结果表明,采用35 kHz和61 kHz两种低频率超声波先后对污泥进行强化处理时,在总处理时间一致的条件下,超声波的顺序和时间分配对污泥活性的提高程度及活性的延续时间无显著差别;采用固定频率的超声波处理时,提高超声波的功率和延长超声作用时间都可以显著提高污泥活性;在功率和作用时间恒定的条件下,增大MLSS对单位质量污泥活性的提高程度影响较小,因此,对污泥先进行浓缩再超声处理可大大提高超声效率.     

污泥好氧消化影响因素分析

结合国内外研究成果,从生物化学反应的角度,对污泥好氧消化中的污泥浓度,溶解氧和 温度等影响因素进行了深入分析。认为好氧消化可作为我国中小型污水处理厂污泥处理的技术措 施,值得进一步研究。     

污泥的自动升温高温好氧消化工艺介绍

自动升温高温好氧消化(ATAD)作为一种污泥稳定工艺,与中、高温厌氧消化和中温好氧消化相比具有反应速度快、停留时间短、占地少、能杀灭病原体、节约能量等诸多优点。对ATAD的运行条件、作用机理及其作用效果进行了综述。     

超声波-好氧生物接触法处理制药废水

试验研究超声波-好氧生物接触法处理制药废水CODCr去除效果.结果表明在超声波处理时间60 s,功率200W时,制药废水单独经超声波处理,CODCr去除率仅为13%～16%;对好氧生物接触反应器中零时刻的混合液澄清水,直接进行好氧生物接触处理,CODCr去除率仅30%左右;而经超声波预处理后再好氧生物接触处理CODCr总去除率达到96%以上.经超声波预处理后,好氧生物接触最佳反应时间为12 h.     

活性炭为载体的好氧颗粒污泥培养及性能研究

好氧颗粒污泥是一种应用于废水生化处理中的新型活性污泥技术,具有结构致密,沉降性能优越,生物处理能力强等特点.通过在气升式内循环间歇反应器启动阶段,接种活性污泥的同时添加活性炭颗粒(AC)的方法,缩短好氧颗粒污泥颗粒化时间,成功培养出了沉降速率大,结构稳定,除氮效果好的活性炭好氧颗粒污泥.并考察了活性污泥絮体-出现颗粒污泥-成熟颗粒污泥-储存-解体-修复的过程,验证了载体强化型好氧颗粒污泥处理低碳氮比废水的可行性.实验结果证明:活性炭好氧颗粒污泥反应器稳定运行时,COD、氨氮、总氮去除率分别可以达到80％ ～ 90％、99％、80％.将成熟活性炭好氧颗粒污泥储存12个月,经过恢复培养,物理特性及脱氮性能能够完全恢复到储存前的水平.     

好氧颗粒污泥快速恢复活性的试验研究

利用正交实验法,采用啤酒废水,在SBR反应器中对在4℃的冰箱中储存7周的好氧颗粒污泥进行活性恢复,观察储存对颗粒污泥的影响及确定颗粒污泥的最佳恢复条件。经过储存的好氧颗粒污泥,其粒径、平均沉降速率无明显变化;上层变黑的好氧颗粒污泥能较快恢复至棕黄色。好氧颗粒污泥恢复活性的最佳操作条件为进水COD持续800 mg/L,水力停留时间8 h,曝气量0.15 m3/h,沉降时间10 min。     

污泥溶胞破解效果与能耗分析

利用超声溶胞作用考察不同浓度下污泥的分解效果。研究结果表明:随着超声波作用时间的延长,污泥中释放出的SCOD和VFA也在不断增加;并且随着污泥浓度的增加,超声污泥释放出的SCOD和VFA不但总量有明显增长,而且单位质量污泥破解释放的SCOD和VFA的量也在增加,在超声作用时间为5～45 min,污泥浓度为13 000 mg/L、17 000 ml/L、37 000 mg/L的情况下,污泥SCOD/VSS的范围为0.10～0.14 mg/mg;VFA/VSS范围为0.016～0.023 mg/mg;当比能耗相同时,随污泥浓度升高,单位质量污泥破解程度显著增加,因此,提高污泥浓度可以在低比能耗的情况下达到较高的能耗效应。     

Effect of low power ultrasound on aerobic/anoxic digestion of activated sludge

The effect of low power ultrasound on aerobic/anoxic digestion of activated sludge was investigated. First, dehydrogenate activity (DHA) and special oxygen uptake rate (SOUR) were detected to indicate the change of biological activity of sludge induced by ultrasound. Single-factor experiments showed that when the ultrasonic frequency was 28 kHz, the optimal ultrasonic density and exposure time were 0.15 W/mL and 10 min, respectively. Through orthogonal tests, the optimal ultrasonic parameters for aerobic/anoxic digestion were found to be a ultrasonic density of 0.15 W/mL, ultrasonic exposure time of 10 min and interval time of 12 h. The aerobic/anoxic digestion was improved by ultrasonic pretreatment, the VSS reduction at the optimal conditions was increased by 35.73%, compared with the control. It can be concluded that low power ultrasonic pretreatment is a valid method for improving aerobic/anoxic biodegradability of activated sludge.     

Frequency effect on p-nitrophenol degradation under conditions of strict acoustic and electric control

The process of decomposing p-nitrophenol (PNP) with power ultrasound requires strict control of acoustic and electric conditions. In this study, the conditions, including acoustic power and acoustic intensity, but not ultrasonic frequency, were controlled strictly at constant levels. The absorbency and the COD concentrations of the samples were measured in order to show the variation of the sample concentration. The results show significant differences in the trend of the solution degradation rate as acoustic power increases after the PNP solution (with a concentration of 114 mg/L and a pH value of 5.4) is irradiated for 60 min with ultrasonic frequencies of 530.8 kHz, 610.6 kHz, 855.0 kHz, and 1130.0 kHz. The degradation rate of the solution increases with time and acoustic power (acoustic intensity). On the other hand, the degradation rate of the solution is distinctly dependent on frequency when the acoustic power and intensity are strictly controlled and maintained at constant levels. The degradation rate of the PNP solution declines with ultrasonic frequencies of 530.8 kHz, 610.6 kHz, 855.0 kHz, and 1130.0 kHz;the COD concentration, on the contrary, increase.     

Thermal pre-treatment of primary and secondary sludge at 70 degrees C prior to anaerobic digestion.

In general, mesophilic anaerobic digestion of sewage sludge is more widely used compared to thermophilic digestion, mainly because of the lower energy requirements and higher stability of the process. However, the thermophilic anaerobic digestion process is usually characterised by accelerated biochemical reactions and higher growth rate of microorganisms resulting in an increased methanogenic potential at lower hydraulic retention times. Furthermore, thermal pre-treatment is suitable for the improvement of stabilization and could be realized at relatively low cost especially at low temperatures. The present study investigates the effect of the pre-treatment at 70 degrees C on thermophilic (55 degrees C) anaerobic digestion of primary and secondary sludge in continuously operated digesters. Thermal pre-treatment of primary and secondary sludge at 70 degrees C enhanced the removal of organic matter and the methane production during the subsequent anaerobic digestion step at 55 degrees C. It also greatly contributed to the destruction of pathogens present in primary sludge. Finally it results in enhanced microbial activities of the subsequent anaerobic step suggesting that the same efficiencies in organic matter removal and methane recovery could be obtained at lower HRTs.     

Minimisation of excess sludge production in a WWTP by coupling thermal hydrolysis and rapid anaerobic digestion.

In many cases, reducing sludge production could be the solution for wastewater treatment plants (WWTP) that here difficulty evacuating the residuals of wastewater treatment. The aim of this study was to test the possibility of minimising the excess sludge production by coupling a thermal hydrolysis stage and an anaerobic digestion with a very short HRT. The tests were carried out on a 2,500 p.e. pilot plant installed on a recycling loop between the clarifier and the actived sludge basin. The line equipped with the full scale pilot plant produced 38% TSS less than the control line during a 10 week period. Moreover, the rapid anaerobic digestion removed, on average, more than 50% of the total COD load with a hydraulic retention time (HRT) of 3 days. Lastly, the dryness of the remaining excess sludge, sanitised by the thermal hydrolysis, was more than 35% with an industrial centrifuge. This combination of thermal hydrolysis and rapid anaerobic digestion equally permits a significant gain of compactness compared to traditional anaerobic digesters.     

功率超声的声学参数对废水处理效果的影响

从功率超声在水处理中的空化机理入手,论述了国内外在应用功率超声进行废水处理时频率、声功率/声强以及声化学反应器的物理结构(实质是声场分布)等声学参数对处理效果的影响。结论表明,对不同的废水溶液存在超声降解的最佳频率和最佳声功率/声强;双频或多频超声较单频超声在处理同一废水溶液时有明显的协同效应;混响场中的空化阈值比行波场低,相同条件下更利于声化学产额的提高。分析了目前超声水处理技术研究不够深入的原因,并对其发展进行了讨论和展望。     

Investigation and assessment of sludge pre-treatment processes.

The pre-treatment of sludges by disintegration will result in a number of changes in sludge properties. Floc destruction as well as cell disintegration will occur. This leads to an increase of soluble substances and fine particles. Furthermore, biochemical reactions may appear during or immediately after disintegration. The influence of disintegration of excess sludge on anaerobic digestion was studied in full scale. A stirred ball mill, an ultrasound disintegrator, a lysate centrifuge and ozone treatment were used. The results of the degradation process were compared to a reference system without pre-treatment. An enhancement of the degree of degradation of 7.4% to 20% was observed. The pollution of sludge water as well as the dewatering properties of the digested sludge were investigated. COD and ammonia in the sludge water were increased and a higher polymer demand was observed while the solid content after dewatering stayed almost unchanged. Based on these results the cost effectiveness has been assessed taking into account different conditions (size of WWTP, cost for disposal, etc.). Capital and energy costs are the main factors while the decrease in disposal costs due to the reduced amount of sludge is the main profit factor.     

A comparison of ultrasound treatment on primary and secondary sludges.

Ultrasound treatment of primary and secondary sludges was conducted to improve the qualities of sludges for the anaerobic digestion. The impacts of different sonication times, sonication densities and solids concentrations on ultrasonication efficiency were examined. The experimental results indicated that the significant reduction in particle size and increase in soluble organics could be achieved, implying that ultrasonication could offer a feasible treatment method to efficiently disintegrate sludge. The greater decrease in particle size and increase in soluble organics of sludge indicated that the secondary sludge has a more remarkable improvement after sonication over the primary sludge. With respects to the extent of disintegration and energy consumption, higher sonication density performed more effectively in terms of specific energy. There exists an optimal solids concentration range for both the sludges for optimum sonication. Within the optimal solids concentration range, efficient sonication can be effected and sludge would be disintegrated efficiently. The ultrasound would be attenuated by scattering and absorption if the solids concentration exceeds the optimal range. It appeared from the study that the mechanical shear forces caused by ultrasonic cavitation could be a key factor for sludge disintegration and collapse of cavitation bubbles could significantly alter the sludge characteristics.     

Reduction of excess sludge production using mechanical disintegration devices.

The usability of mechanical disintegration techniques for the reduction of excess sludge production in the activated sludge process was investigated. Using three different disintegration devices (ultrasonic homogeniser, stirred media mill, high pressure homogeniser) and different operational parameters of the disintegration, the effect of mechanical disintegration on the excess sludge production and on the effluent quality was studied within a continuously operated, laboratory scale wastewater treatment system with pre-denitrification. Depending on the operational conditions and the disintegration device used, a reduction of excess sludge production of up to 70% was achieved. A combination of mechanical disintegration with a membrane bioreactor process with high sludge age is more energy effective concerning reduction of sludge production than with a conventional activated sludge process at lower sludge ages. Depending on the disintegration parameters, the disintegration has no, or only minor, negative effect on the soluble effluent COD and on the COD-removal capacity of the activated sludge process. Nitrogen-removal was slightly deteriorated by the disintegration, whereas the system used was not optimised for nitrogen removal before disintegration was implemented.     

Performance of high-rate sludge digesters fed with sonicated sludge.

A major limitation of anaerobic sludge digestion is the long hydraulic retention time (HRT) required for satisfactory stabilization which results in large digester size. This study explored a possibility of operating digesters at shortened HRTs by sonication pretreatment of secondary sludges. Four identical digesters designated D1, D2, D3 and D4 were fed with untreated and sludge sonicated at densities of 0.18 W/ml, 0.33 W/ml and 0.52 W/ml, respectively. All digesters were operated at three HRTs of 8-day, 4-day and 2-day. Comparing with the control digester (D1), total solids removal efficiencies improved by 12-19%, 17-36% and 20-39% in digesters D2, D3 and D4, respectively. The volatile solids removal was also increased by 11-21%, 17-33% and 19-36% in the respective digesters. The improved solids degradation corresponded with increase in biogas production by 1.4-2.5, 1.9-3.0 and 1.6-3.1 times, respectively. Increase in methane composition by 2-17% was also noted in all digesters fed with sonicated sludge. An analysis indicated that sonication pretreatment could enhance degradation of carbon, nitrogen and sulfur substances in the digestion. The study suggested that sonication of sludge is a possible pretreatment to shorten the digester operating HRT with improvement in solids degradation, biogas production and methane content. It can be deduced that to maintain a consistent solids loading at a desire performance, sludge digester with smaller size can be designed.