ATP content and biomass activity in sequential anaerobic／aerobic reactors

Specific ATP content of volatile solids was measured to characterize the sludge activity in a sequential anaerobic/aerobic wastewater treatment system, with an upflow anaerobic sludge blanket (UASB) reactor and a three-phase aerobic fluidized bed (AFB) reactor. The wastewater COD level was 2000-3000 mg/L in simulation of real textile wastewater. The ATP content and the specific ATP contents of volatile solids at different heights of the UASB reactor and those of the suspended and immobilized biomass in the AFB reactor were measured. In the UASB reactor, the maximum value of specific ATP (0.85 mg ATP/g VS) was obtained at a hydraulic retention time (HRT) 7.14 h in the blanket solution. In the AFB reactor, the specific ATP content of suspended biomass was higher than that of immobilized biomass and increased with hydraulic retention time reaching a maximum value of 1.6 mg ATP/g VS at hydraulic retention time 4.35 h. The ATP content of anaerobes in the UASB effluent declined rapidly under aerobic conditions following a 2nd-order kinetic model.

Function of anaerobic portion in a conventional sequencing batch reactor

The performance of SBRs treating two kinds of wastewater(synthetic wastewater con- taining polyvinyl alcohol and effluent from a coke-plant wastewater treatment system)was investi- gated in this study,in order to examine the exact function of anaerobic portion in a conventional SBR.The set up of 4-or 8-hour anaerobic mixing period in a SBR's cycle did not benefit for PVA degradation.While an anaerobic reactor seeded with anaerobic sludge could partly hydrolyse and acidify PVA into readily-degradable intermediates.During the anaerobic fill period of an SBR treat- ing the effluent from a coke-plant wastewater treatment system,the organic concentration was re- duced to certain extent due to the adsorption of activated sludge and dilution of the mixed liquor from the previous cycle.Parts of readily-degradable organics in the influent were utilised by denitri- fiers as carbon source.The biomass in a conventional SBR was alternatively imposed to aerobic and anaerobic conditions in its operating cycle,the environmental conditions needed for anaerobic hy- drolization and acidification of refractory organics could not occur in such an SBR.

Elimination of Carbon, Nitrogen and Phosphorus in Domestic Wastewater through a Series of Anaerobic and Aerobic Reactors for a Developing Country like Benin

Waste water treatment in order to preserve water resources is one of the major concerns in developing countries. This study aims to test the operating effectiveness of a pilot designed on a basis of several laboratory experiments, which consists of an anaerobic and aerobic pond in series. The test was performed through monitoring global parameters of pollution. The results of the analysis of these parameters indicate an elimination of 91% of suspended solids, 68% of COD, 77% of BOD5, 61% of nitrate and 81% of phosphorus. It was also noticed that the anaerobic pond removes most, carbonaceous organic materials and especially suspended matters;and the aerobic pond most, nitrogen and especially phosphorus. This study reveals the effectiveness of the series connection of an anaerobic and aerobic pond for domestic wastewater treatment.

Removal of nitrogen and phosphorus in a combined A^2/O-BAF system with a short aerobic SRT

A bench-scale anaerobic/anoxic/aerobic process-biological aerated filter （A^2/O-BAF） combined system was carded out to treat wastewater with lower C/N and C/P ratios. The A^2/O process was operated in a short aerobic sludge retention time （SRT） for organic pollutants and phosphorus removal, and denitrification. The subsequent BAF process was mainly used for nitrification. The BAF effluent was partially returned to anoxic zone of the A^2/O process to provide electron acceptors for denitrification and anoxic P uptake. This unique system formed an environment for reproducing the denitdfying phosphate-accumulating organisms （DPAOs）. The ratio of DPAOs to phosphorus accumulating organisms （PAOs） could be maintained at 28% by optimizing the organic loads in the anaerobic zone and the nitrate loads into the anoxic zone in the A^2/O process. The aerobic phosphorus over-uptake and discharge of excess activated sludge was the main mechanism of phosphorus removal in the combined system. The aerobic SRT of the A^2/O process should meet the demands for the development of aerobic PAOs and the restraint on the nitrifiers growth, and the contact time in the aerobic zone of the A^2/O process should be longer than 30 min, which ensured efficient phosphorus removal in the combined system. The adequate BAF effluent return rates should be controlled with 1--4 mg/L nitrate nitrogen in the anoxic zone effluent of A^2/O process to achieve the optimal nitrogen and phosphorus removal efficiencies.

A novel approach to treat combined domestic wastewater and excess sludge in MBR

Domestic wastewater was treated by combined anaerobic biofilm aerobic membrane bioreactor(MBR) process, and part biomass in MBR was withdrawn to treat with ozone, then the ozonated sludge was returned to anaerobic inlet. In aerobic MBR, MLSS and DO were controlled at 3000—3500 mg/L and 0 8 mg/L respectively. Comparing the experimental results of two stages, it was noticed that ozonation did not affect the removal efficiency for organics but had a significant influence on the removals of NH 3 N and TN. During the ozonation period of two months, no excess sludge was wasted, and a zero sludge yield was obtained.

Petro-chemical wastewater treatment by biological process

In order to study the feasibility of treating petro chemical wastewater by the combination of anaerobic and aerobic biological process, a research of treating wastewater in UASB reactor and aeration basin has been conducted. The test results shows that under moderate temperature, with 5\^2 kgCOD/(m\+3·d) volumetric load of COD Cr in the UASB reactor and 24h of HRT, 85% removal rate of BOD 5 and 83% of COD \{Cr\} and 1\^34 m\+3/(m\+3·d) volumetric gas production rate can be obtained respectively. The aerobic bio degradability can be increased by 20%—30% after the petro chemical wastewater has been treated by anaerobic process. As Ns=0\^45 kgCOD/(kgMLSS·d), HRT=4h in the aeration tank, 94% removal rate of BOD 5, 93% of COD \{Cr\}, 98\^8% total removal rate of COD \{Cr\} and 99% removal rate of BOD 5 can be reached.

Simulation of sludge－dredging effects in controlling nutrient release of LakeKasumigaura with large－size core samples

Nutrient release from the dredged and undredged sediments in Lake Kasumigaura were simulated under the laboratory control conditions with large-size core samples. It was found that phosphate and ammonia release fluxes are less in aerobic than those in anaerobic. In different simulated dredged depth, the phosphate release showed large divergence in the anaerobic than in the aerobic. There was a larger accumulated release of phosphate and ammonia at actual dredged (St. B) than the undredged (St. A) in anaerobic condition. This showed that the sludge-dredging was effective of controlling phosphorus and nitrogen release. A preliminary assessment is drawn from the experiments that the sludge-dredging work in Tsuchiura Bay of Lake Kasumigaura can reduce about 15. 9% of phospbate and 56. 2% of anunonia release from the sediments respectively.

Elucidating the removal mechanism of N,N-dimethyldithiocarbamate in an anaerobic-anoxic-oxic activated sludge system

N,N-Dimethyldithiocarbamate （DMDTC） is a typical precursor of N-nitrosodimethylamine （NDMA）. Based on separate hydrolysis, sorption and biodegradation studies of DMDTC, a laboratory-scale anaerobic-anoxic-oxic （AAO） system was established to investigate the removal mechanism of DMDTC in this nutrient removal biological treatment system. DMDTC hydrolyzed easily in water solution under either acidic conditions or strong alkaline conditions, and dimethylamine （DMA） was the main hydrolysate. Under anaerobic, anoxic or oxic conditions, DMDTC was biodegraded and completely mineralized. Furthermore, DMA was the main intermediate in DMDTC biodegradation. In the AAO system, the optimal conditions for both nutrient and DMDTC removal were hydraulic retention time 8 hr, sludge retention time 20 day, mixed-liquor return ratio 3：1 and sludge return ratio 1：1. Under these conditions, the removal efficiency of DMDTC reached 99.5%; the removal efficiencies of chemical organic demand, ammonium nitrogen, total nitrogen and total phosphorus were 90%, 98%, 81% and 93%, respectively. Biodegradation is the dominant mechanism for DMDTC removal in the AAO system, which was elucidated as consisting of two steps： first, DMDTC is transformed to DMA in the anaerobic and anoxic units, and then DMA is mineralized to CO2 and NH3 in the anoxic and oxic units. The mineralization of DMDTC in the biological treatment system can effectively avoid the formation of NDMA during subsequent disinfection processes.

Effect of Oxygen and Bacteria on the Property of Polymer Gel

The viscosity property of Cr^3＋, Al^3＋, and compound ion cross-linked polymer gel solution in the anaerobic and aerobic environment was investigated aiming at meeting the practical demand of the oil field. The viscosity reserving effect after adding the biocide and the gelation in the anaerobic and aerobic environments was also studied in the paper. The results indicate that the viscosity of the cross-linked polymer gel solution caused by the water produced in aerobic environment is higher than that in anaerobic environment, and that the viscosity value of the cross-linked polymer gel solutions after adding biocides has improved to some extent and polymer gel has gelated well in anaerobic environment.

A reactor system combining reductive dechlorination with co-metabolic oxidation for complete degradation of tetrachloro-entylene

A laboratory sequential anaerobic aerobic bioreactor system, which consisted of an anaerobic fixed film reactor and two aerobic chemostats, was set up to degrade tetrachloroethylene (PCE) without accumulating highly toxic degradation intermediates. A soil enrichment culture, which could reductively dechlorinate 900 μM (ca. 150 mg/L) of PCE stoichiometrically into cis 1,2 dichloroethylene ( cis DCE), was attached to ceramic media in the anaerobic fixed film reactor. A phenol degrading strain, Alcaligenes sp. R5, which can efficiently degrade cis DCE by co metabolic oxidation, was used as inoculum for the aerobic chemostats consisted of a transformation reactor and a growth reactor. The anaerobic fixed film bioreactor showed more than 99 % of PCE transformation into cis DCE in the range of influent PCE concentration from 5 μM to 35 μM at hydraulic retention time of 48h. On the other hand, efficient degradation of the resultant cis DCE by strain R5 in the following aerobic system could not be achieved due to oxygen limitation. However, 54% of the maximum cis DCE degradation was obtained when 10 μmol of hydrogen peroxide (H 2O 2) was supplemented to the transformation reactor as an additional oxygen source. Further studies are needed to achieve more efficient co metabolic degradation of cis DCE in the aerobic reactor.

Effect of Sludge Retention Time on the Fate of Proteins and Polysaccharides in AAO Process

Effect of sludge retention time( SRT) on the removal of potential and polysaccharides in an anaerobic / anoxic / aerobic( AAO) process was investigated. The Lowry method and anthrone method were used to detect proteins and polysaccharides. Total removal efficiency of proteins at SRT of 10 to 25 d in the AAO system was higher than 90%. Polysaccharides removal efficiencies were above 80% when SRT was increased from 15 to 25 d,whereas only 81% of polysaccharides was removed at SRT of 10 d. The biodegradation part of proteins and polysaccharides increased from87. 40% to 93% and from 74. 22% to 86. 94% with increasing SRTs.The ratios of polysaccharides and proteins in extracellular polymer substances( EPSs) were around 1. 5-3 in different SRTs. As SRT increasing,polysaccharides and proteins discharged with residual sludge decreased gradually. The amount of EPSs decreased with increasing SRTs.

Covalent-organic frameworks with keto-enol tautomerism for efficient photocatalytic oxidative coupling of amines to imines under visible light

Photocatalytic oxidation of organic molecules into highly value-added products is an innovative and challenging research which has gradually attracted remarkable attention of scientists.In this work,it is demonstrated that the COF-TpPa with keto-enol tautomerism equilibrium structure shows excellent performance(yield>99%after 8 h)in the selective photocatalytic oxidative coupling of amines to imines under visible light irradiation.It is revealed that three kinds of reactive oxygen species(superoxide radical,hydroxyl radical and singlet oxygen)participate in this photocatalytic oxidation reaction.In addition,hydrogen protons cleaved from the benzyl are proven to be reduced to hydrogen in the conduction band of COF-TpPa in anaerobic atmosphere,accompanied with the formation of imines.The direct hydrogen evolution from amine provides an effective way to extract clean energy from organic molecule as well as the production of value-added chemicals.As a contrast,COF-LZU1 with similar structure and chemical composition to COF-TpPa but without keto-enol tautomerism exhibits worse optical properties and photocatalytic performance.It is also demonstrated that keto-enol tautomerism favors the adsorption of benzylamine based on the characterization results and theoretical calculations.