นิตยา ผาสุขพันธุ์. Removal of Organic Substances and Reactive Azo Dye by Anaerobic/Aerobic Biological Activated Carbon Sequencing Batch Reactor. Doctoral Degree(Environmental Technology). King Mongkut's University of Technology Thonburi. KMUTT Library. : King Mongkut's University of Technology Thonburi, 2010.
Removal of Organic Substances and Reactive Azo Dye by Anaerobic/Aerobic Biological Activated Carbon Sequencing Batch Reactor
Abstract:
The aim of this research is to investigate the capability of Anaerobic/Aerobic
Biological Activated Carbon Sequencing Batch Reactor (A/A BAC-SBR) for
organic substances and dye removal. The experiments were divided into 2 phases;
phase I was designed in order to determine the main removal mechanisms in the
system and phase II was reactor operation that studied effect of SBR operation
parameters. Each of BAC system composition; granular activated carbon (GAC),
microorganism (MC) and immobilized cell on GAC or biological activated carbon
(BAC) was studied. The removal efficiency on various conditions; BAC
composition type, BAC composition dosage, test solution and operating condition
(anaerobic and/or aerobic batch operation or SBR operation) were also
investigated. Furthermore, the data from this phase was used for determination of
kinetic parameters by simple chemical equations and the appropriate condition for
SBR operation in phase I and reactor operation in phase II.
The preliminary results showed that the acclimatized microorganisms were more
effectively remove dye than non acclimatized microorganisms by shorten the
retention time with no lag phase. Besides, the result showed that anaerobic
condition was important for dye removal and the appropriate anaerobic retention
time was 35 h. On the other hand, GAC and the acclimatized microorganism
dosages were decided to use at 3000 mg/L and 5000 mg/L, respectively due to dye
removal efficiency and economic concern reasons.
As for the study ofBAC system composition, the batch experiments were followed
to SBR periods; Fill, React (anaerobic: aerobic), Settle, Draw and Idle. The results
indicated GAC and MC played role in dye removal. It was found that desizing
agent disturb dye adsorption capability by GAC but support MC decolorization by
acting as co-substrate. Removal of organic substance and dyes was observed in all
periods of SBR cycle batch test, it was found that organic substances and dyes
were rapidly decreased in Fill period. The kinetic studies showed that dye
biodegradation fitted to second order reaction which indicated that decolorization
was depended on dye and co-substrate concentrations.
As for reactor operation, the appropriate conditions from phase I were used. The
A/A BAC-SBR was operated with 5000 mg/L and 3000 mg/L ofMC and GAC at
the beginning, respectively. SBR cycle consisted of Fill 1.5 h, React 43 h
(anaerobic: aerobic; 35 : 8), Settle 2.5 h, Draw 0.5 h and Idle 0.5 h for 48 h/cycle.
A/A SBR and AlA BAC-SBR were set up to study the effect of SRT and initial
dye concentration on COD and dye removal efficiency. The results showed that
increasing SRT from 3 to 15 days could not lead to significant higher COD and
dye removal.
On the other hand, increasing initial dye concentration from 100 mg/L to 500
mg/L resulted in decreasing COD removal of A/A SBR and AlA BAC-SBR
probably due to the accumulation of by-products from dye degradation. GAC
replacement was performed at the end of anaerobic phase at every 7th cycle in
order to reduce the intermediates from biodegradation before discharging. It was
found that replacement could not raise dye removal but it clearly showed the
possibility to decrease dye intermediates that probably toxic to microorganisms in
SBR. GC-MS technique was used for identification dye intermediate compounds.
Detectable peaks were appeared during anaerobic and aerobic phase. This showed
that operation in same basin could not bring about completely remove dye
intermediate under anaerobic/aerobic condition of this study. However, overall
organic substance and dye removal in this research was in the range of discharge
standards. Therefore, the advance treatment should be employed to minimize toxic
accumulation in the system and effluent. In this research, GAC replacement shows
the possibility to support decreasing toxic level in effluent of BAC system. After
replacement of exhausted GAC (BAC) with virgin GAC in A/A BAC-SBR, the
detectable peaks were significantly decreased. Therefore, A/A BAC system with
GAC replacement shows trend to completely remove dye and its intermediates
from textile wastewater and bring about decreasing toxic level in treatment system
and receiving water.