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Frontiers of Environmental Science & Engineering

Front. Environ. Sci. Eng.    2018, Vol. 12 Issue (5) : 5
Investigate of in situ sludge reduction in sequencing batch biofilm reactor: Performances, mechanisms and comparison of different carriers
Yonglei Wang1,2,3(), Baozhen Liu1,2, Kefeng Zhang1,2, Yongjian Liu4, Xuexin Xu1, Junqi Jia1
1. School of Municipal and Environmental Engineering, Shandong Jianzhu University, Jinan 250101, China
2. Co-Innovation Center of Green Building, Jinan 250101, China
3. Shandong Province City Water Supply and Drainage Water Quality Monitoring Center, Jinan 250101, China
4. Shandong Huaihe River Basin Water Conservancy Administration Planning and Design Institute, Jinan 250101, China
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Microbial metabolism uncoupling, sludge decay is the main mechanism to promote in situ sludge reduction on this biofilm system.

The main reduction mechanism inside the biofilm is sludge decay in the longitudinal distribution of biofilm.

Mizugakiibacter and Azospira anaerobic fermentation bacterium dominate the FSC organisms indicating the dominant mechanism on the biofilm is sludge decay.

The floating spherical carriers with compound of the polyurethane and two fiber balls can effectively blocking suspended sludge, improving Biofilm formation efficiency significantly.

Biofilm is an effective simultaneous denitrification and in situ sludge reduction system, and the characteristics of different biofilm carrier have important implications for biofilm growth and in situ sludge reduction. In this study, the performance and mechanism of in situ sludge reduction were compared between FSC-SBBR and SC-SBBR with constructed by composite floating spherical carriers (FSC) and multi-faceted polyethylene suspension carriers (SC), respectively. The variation of EPS concentration indicated that the biofilm formation of FSC was faster than SC. Compared with SC-SBBR, the FSC-SBBR yielded 0.16 g MLSS/g COD, almost 27.27% less sludge. The average removal rates of COD and NH4+ -N were 93.39% and 96.66%, respectively, which were 5.21% and 1.43% higher than the average removal rate of SC-SBBR. Investigation of the mechanisms of sludge reduction revealed that, energy uncoupling metabolism and sludge decay were the main factors for sludge reduction inducing 43.13% and 49.65% less sludge, respectively, in FSC-SBBR. EEM fluorescence spectroscopy and SUVA analysis showed that the hydrolytic capacity of biofilm attached in FSC was stronger than those of SC, and the hydrolysis of EPS released more DOM contributed to lysis-cryptic growth metabolism. In additional, Bacteroidetes and Mizugakiibacter associated with sludge reduction were the dominant phylum and genus in FCS-SBBR. Thus, the effect of simultaneous in situ sludge reduction and pollutant removal in FSC-SBBR was better.

Keywords In situ sludge reduction      Biofilm      Composite floating spherical carriers      Microbial community      SBBR     
Corresponding Authors: Yonglei Wang   
Issue Date: 25 September 2018
 Cite this article:   
Yonglei Wang,Baozhen Liu,Kefeng Zhang, et al. Investigate of in situ sludge reduction in sequencing batch biofilm reactor: Performances, mechanisms and comparison of different carriers[J]. Front. Environ. Sci. Eng., 2018, 12(5): 5.
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Yonglei Wang
Baozhen Liu
Kefeng Zhang
Yongjian Liu
Xuexin Xu
Junqi Jia
Abbreviation Full name
CAS Conventional activated sludge
COD Chemical oxygen demand
DOC Dissolved organic carbon
DO Dissolved oxygen
DOM Dissolved organic matter
EAS Excess activated sludge
EEM Emission electron microscope
EPS Extracellular polymeric substances
FSC Composite floating spherical carries
HRT Hydraulic retention time
FSC-SBBR Sequencing batch biofilm reactor with composite floating spherical carries
SC-SBBR Sequencing batch biofilm reactor composite floating spherical carries
MLSS Mixed liquor suspended solids
MLVSS Mixed liquor volatile suspended solids
PN Protein
PS Polysaccharide
SBBR Sequencing batch biofilm reactor
SC Multi-faceted polyethylene suspension carriers
SOUP Specific oxygen uptake rate
SATP Specific adenosine triphosphate
SUVA Specific ultraviolet absorbance
SMP Soluble microbial products
TN Total nitrogen
TP Total phosphorus
Yobs Sludge observed yield
Tab.1  Abbreviated list
Fig.1  Schematic diagram of experimental FSC-SBR, SC-SBBR, FSC and SC.
Carriers Height (mm) Diameter (mm) Density (kg·m3) Specific surface area (m2·g1) Water-holding capacity
FSC 60 1.21–1.23 2.15–2.21 452.38%
SC 60 50 0.96–0.98 1.23–1.25 5.41%
Tab.2  Technical parameters of floating spherical and suspended carriers
Run Temperature (°C) HRT (h) DO (mg·L1)
1 (0–15 d) 15 12 4–5
2 (15–30 d) 20 12 4–5
3 (30–45 d) 25 12 4–5
4 (45–60 d) 30 12 4–5
5 (60–75 d) 25 8 4–5
6 (75–90 d) 25 6 4–5
7 (90–105 d) 25 12 2–3
8 (105–120 d) 25 12 6–7
Tab.3  Operating conditions in different stages
Fig.2  Variation of MLSS (a), the cumulative sludge production (b) and daily Yobs (c) in FSC-SBBR and SC-SBBR (the numbers 1–8 represent the different operating conditions listed in Table 2).
Fig.3  The variations in biofilm (a) FSC, (b) SC.
System Yobs (g MLSS/g COD)
1 2 3 4 5 6 7 8
FSC-SBBR 0.32±0.200 0.25±0.097 0.12±0.069 0.24±0.148 0.23±0.084 0.37±0.138 0.21±0.094 0.35±0.214
SC-SBBR 0.77±0.197 0.35±0.078 0.18±0.083 0.32±0.122 0.25±0.118 0.36±0.207 0.22±0.134 0.46±0.208
Tab.4  Values of Yobs in FSC-SBBR and SC-SBBR under different operating conditions
Fig.4  The variation of EPS (a), concentration of DOM in the supernatant at the end of the sludge decay trial experiment (b), the variation of ATP contents contained in sludge and MLSS from different stages (c), ATP contents contained at different distances of FSC and SC from the surface to the bottom (d), and the variation of SOUR under different HRT (e) and in the different distance from the surface to the inside of the biofilm (f).
System Initial MLSS (g·L1) Final MLSS (g·L1) ΔMLSS (g·L1) SRR
FSC-SBBR 1.015±0.078 1.044±0.071 0.029±0.007 43.13%
SC-SBBR 1.588±0.326 1.639±0.271 0.051±0.055
Tab.5  The values of MLSS variation and sludge-reduction ratio (SRR) of energy-uncoupling metabolism in FSC-SBBR and SC-SBBR
Fig.5  The EEM-DOM fluorescence spectra of FSC-SBBR (a-influent, c-anaerobic phase and e-effluent), and SC-SBBR (b-influent, d-anaerobic phase, f-effluent).
System SUVA
Temperature (°C) HRT/h
25 30 6 8 12
FSC-SBBR 0.71±0.063 0.58±0.188 0.73±0.168 0.78±0.108 0.83±0.144
SC-SBBR 0.56±0.078 0.55±0.231 0.58±0.122 0.63±0.153 0.61±0.098
Tab.6  SUVA (L/mb-Cm) of effluent in FSC-SBBR and SC-SBBR under different operating conditions
Phase COD (mg·L1) COD removal ratio (%) Polysaccharides (mg·L1) SUVA (L/mb-Cm)
Influent 230±14.80 10.94±1.29 0.009±0.003
Anoxic 164±5.57 28.70±0.82 15.21±1.16 0.033±0.017
Anaerobic 124±6.22 46.09±1.02 14.24±2.84 0.032±0.019
Aerobic 30 min 72±4.36 68.70±2.16 14.35±3.02 0.426±0.015
Aerobic 60 min 52±3.00 77.9±2.52 10.71±1.78 0.420±0.032
Aerobic 90 min 36±4.85 84.35±4.14 11.76±1.33 0.980±0.087
Tab.7  Variation of DOM in the supernatant during an operating cycle period in FSC-SBBR (HRT=12 h)
Fig.6  SEM photographs of the biofilm sampled from FSC-SBBR (a) SC-SBBR (b) at different distances from the surface to the bottom of the carriers.
Fig.7  Microbial community structures of FSC-SBBR and SC-SBBR based on 454 pyrosequencing at the phylum level (a) and the genus level (b).
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