Study on Limited Filamentous Sludge Bulking Test in A/O Activated Sludge Process

[Objective] This study aimed to make use of the limited filamentous sludge bulking characteristics to purify water quality and save energy. [Method] The effects of dissolved oxygen （DO） on sludge bulking were explored by changing the DO con- centration in the aerobiotic pool of NO system from the low load （0.25 kg COD/（kg MLSS.d）） and the medium to high load （0.55 kgCOD/（kg MLSSod））. [Result] In the NO activated sludge system, when the sludge load was 0.25 kg COD/（kg MLSS.d）, DO=1.5 mg/L, the sludge index was at around 250, while when the sludge load- ing was 0.55 kg COD/（kg MLSS.d）, DO=1.5 mg/L, the sludge index was close to 300, occurring the limited filamentous bulking. The bulked sludge still showed high removal rates to COD, SS, nitrogen and phosphorus. [Conclusion] It could improve the oxygen transfer rate and reduce the aeration rate at low DO conditions to achieve energy-saving.

Performance evaluation of up-flow anaerobic sludge blanket(UASB) reactor for treatment of paper mill wastewater

The present study deals with the performance evaluation of the UASB reactor under varied organic loading rate(OLR) for the treatment of paper mill wastewater. The sludge granulation process started after 120 days from the start-up period. Sludge granules size was found to be 0 8 mm at OLR of 1 72 kgCOD/(m 3·d), which reached maximum size of about 1 0 to 1 2 mm at OLR of 2 1 kgCOD/(m 3·d). At the end of initial OLR of 1 0 kgCOD/(m 3·d) the VSS concentration was 12 86 gVSS/L, which got increased to 38 05 gVSS/L at the end of an OLR 2 1 kgCOD/(m 3·d). Most of the times VFA recorded were well within the limit of VFA reported in anaerobic fermentation process. Many times the pH observed was between 6 5 and 7 8, which is more favorable for any anaerobic process. It is also found that pH within the reactor increases along with the height of reactor. The total maximum biogas production was found to be 0 40 L/gCOD removals at OLR of 2 1 kgCOD/(m 3·d) and the maximum BOD removal at this stage was observed to be 90%.

Optimizing Conditions of Enhancing Granule Sludge Concentration and Performance

An expanded granular sludge bed （EGSB） reactor was adopted to study the influence factors and rule of enhancing granular sludge concentration and performance. The experiment was performed at 33 ℃, pH 6.0-8.0 with continuous flow by adding proper quantity of nutritional trace elements. The results show that SLR was the key of steady operation of EGSB reactor. The increment of the granular sludge was influenced by volume loading rate （VLR）, liquid up-flow velocity and sludge loading rate （SLR）. Concentration of granular sludge increased rapidly when liquid up-flow velocity was over 0.94 m · h^-1 with SLR being at 1.0-2.0 d ^-1. With the propriety parameters： liquid up-flow velocity 2.52 m · h^-1, SLR 1.0-2.2 d^-1 and VLR 8.2-13.1 kg · m ^3 · d^-1, 23 days＇ continuous operation resulted in an increment by over 80% of granular sludge concentration in the EGSB reactor, plus good granular sludge property.

Sanitary Sewage Treatment with Jet Inner-loop Bioreactor

A jet inner-loop bioreactor (JIBR) was used to treat synthetic sanitary sewage with low, medium and high COD load. The experimental results show that it could meet discharge standard at 20\|30 min of HRT (hydraulic retention time) for low COD concentration and 60\|120 min of HRT for medium and high COD concentration. The maximal COD volume loading and COD sludge loading of 27 kg\5m -3 \5d -1 and 5 kg/d per kg MLSS were acheived respectively, that were 10\|20 times higher than those of traditional wastewater treatment processes. The BOD 5 removal efficiency was more than 90% and NH + 4 —N more than 85%. The study on the activity showed that the oxygen consumption rate of the activated sludge in the JIBR was 39.13 mg\5L -1 \5h -1 , which was 1.7 times higher than that of the SBR(Sequencing Batch Reactor) and the dominant bacteria in jet inner\|loop bioreactor was Pseudomonas species.

Control strategy of simultaneous nitrification and denitrification in SBR system

The influence of main process parameters on simultaneous nitrification and denitrification （SND） in a sequencing batch reactor （SBR） were investigated while treating actual municipal sewage. The influent average concentration of CODcr and total nitrogen was 350mg-L-l and 35mg.L-l. The experiment indicated the following four operation control strategies： （1） When operation cycle was 6 hours, oxidation of organic pollutants and simultaneous nitrification and denitrification could well completed in the SBR reactor; （2） TN removal rate could be increased significantly, 40% higher than traditional SBR processes when idle period was set between influent and aeration; （3） The time of idle period could affect simultaneous nitrification and denitrification and the best time is 30 minutes; （4） Increase of sludge organic load may improve TN removal efficiency, but NH3-N removal efficiency declines.

Continuous biohydrogen production from diluted molasses in an anaerobic contact reactor

An anaerobic contact reactor (ACR) systemcomprising a continuous flow stirred tank reactor (CSTR)with settler to decouple the hydraulic retention time(HRT) from solids retention time (SRT) was developedfor fermentative hydrogen production from dilutedmolasses by mixed microbial cultures. The ACR wasoperated at various volumetric loading rates (VLRs) of20-44 kgCOD·m^(-3)·d^(-1) with constant HRT of 6 h undermesophilic conditions of 35°C. The SRTwas maintained atabout 46-50 h in the system. At the initial VLR of20 kgCOD·m^(-3)·d^(-1), the hydrogen production rate droppedfrom 22.6 to 1.58 L·d^(-1) as the hydrogen was consumed bythe hydrogentrophic methanogen. After increasing theVLR to 28 kgCOD·m^(-3)·d^(-1) and discharging the sludge for6 consecutive times, the hydrogentrophic methanogenswere eliminated, and the hydrogen content reached 36.4%.As the VLR was increased to 44 kgCOD·m^(-3)·d^(-1), thehydrogen production rate and hydrogen yield increased to42.1 L·d^(-1) and 1.40 mol H2·molglucose-consumed^(-1),respectively. The results showed that a stable ethanoltypefermentation that favored hydrogen production inthe reactor was thus established with the sludgeloading rate (SLR) of 2.0-2.5 kgCOD·kgMLVSS-1·d^(-1).It was found that the ethanol increased more than otherliquid fermentation products, and the ethanol/acetic acid(mol/mol) ratio increased from 1.27 to 2.45 when the VLRincreased from 28 to 44 kgCOD·m^(-3)·d^(-1), whereas thehydrogen composition decreased from 40.4% to 36.4%.The results suggested that the anaerobic contact reactorwas a promising bioprocess for fermentative hydrogenproduction.