J Mater Cycles Waste Manag DOI 10.1007/s10163-017-0597-1
ORIGINAL ARTICLE
Centrifugal dewatering of blended sludge from drinking water treatment plant and wastewater treatment plant Ailan Yan1,2 · Jun Li1,3 · Liu Liu4 · Ting Ma3 · Jun Liu1 · Yongjiong Ni3
Received: 19 April 2016 / Accepted: 2 February 2017 © Springer Japan 2017
Abstract The blended sludge taken from drinking water treatment plant (WTP) and wastewater treatment plant (WWTP) for centrifugal dewatering was proposed. Residual products of polyaluminum chloride and inorganic particles in alum sludge from WTP were considered to improve dewaterability of sewage sludge from WWTP through the charge neutralization, adsorption bridging, squeezing, and skeleton builders. The sludge with blend ratio of 1:1 and no PAM addition, the specific resistance to filtration was 1.27 × 1013 m/kg, the moisture content was 62% after centrifugal dewatering, and more excellent dewatering performance of blended sludge was proved. Scanning electron microscope showed that the surface of blended sludge had more rough and porosity structure than the sewage sludge. EDS analysis showed that residual alum and inorganic particles existed in blended sludge. 3D-Excitation-emission matrix was used to analyze change of protein-like of sewage sludge and blended sludge with dewatering process. The results implied that alum sludge acted as chemical conditioner and physical conditioner in blended sludge. A hypothesis was suggested to describe the centrifugal dewatering process of blended sludge. The final disposal options * Jun Li
[email protected] 1
College of Environment, Zhejiang University of Technology, No. 18, Chao Wang Road, Hangzhou 310014, China
2
Zhejiang University of Water Resources and Electric Power, No. 583, Xue Lin Street, Hangzhou 310018, China
3
College of Civil Engineering and Architecture, Zhejiang University of Technology, No. 18, Chao Wang Road, Hangzhou 310014, China
4
Hangzhou Urban and Rural Construction Design Institute Co., Ltd., No. 22, Gu Jia Fan Road, Hangzhou 310010, China
of the blended sludge would be landfilling and building material utilization. Keywords Blended sludge · Alum sludge · Centrifugal dewatering · Moisture content · 3D-EEM
Introduction Municipal wastewater treatment plants produce a large amount of sludge which contains more than 98% water, and the volume of the sewage sludge should be reduced before final disposal [1]. However, the dewatering of sewage sludge is a major challenge to the wastewater treatment process [2], because of its extreme solids compressibility caused by its highviscosity resulted from highly negative chargedsmall particles and large amounts of organic content including extracellular polymers. In the present, the sewage sludge is pretreated with kinds of chemical and physical conditioners before dewatered [3]. The role of chemical conditioner is to destroy the sludge colloid stability, neutralize the electrical property, and adsorb bridging. The chemical conditioners include chloride, polyacrylamide, calcium oxide, and ferric, etc [4]. Cationic polyacrylamide (CPAM) is one of the common used polymer organic chemicals conditioner in sludge dewatering, and it can flocculate the sludge particles and improve the sludge dewatering rate [5]. However, it is more difficult to find the exact PAM dosage in the sludeg dewatering process for the PAM dosage depends on the sewage sludge concentration and the sludge colloid property. Excessive consumption of PAM will increase the cost of sludge treatment, while insufficient amount of PAM will affect the effect of sludge dewatering [6]. Therefore, chemical conditioning has difficulties to improve the sludge cake
13
Vol.:(0123456789)
solids content in the mechanical dewatering, for the sewage sludge which is often hindered by blinding of the filter cake itself and the filtration media [7]. In addition, PAM may cause secondary contamination. Physical conditioners are used as skeleton builders or filter aids to reduce the sludge compressibility and improve the sludge mechanical strength and permeability. During the mechanical dewatering, these physical conditioners can form more permeable rigid lattice to maintain porosity structure [3]. Many inorganic particles can be used as the skeleton, including fly ash, gypsum, lime, lignite, sawdust, wheat residue, fiber, rice bran, red mud, struvite stone, seafood shell, and humus [8–14]. As a result, all of these inorganic particles could improve sludge dewaterability and the lowest moisture content can be reduced to 70% [15]. The polyaluminum chloride (PACl) flocculant is commonly used in drinking water treatment plants and large amount of alum sludge is produced. Therefore, if the alum sludge is not appropriately disposed, it may cause serious environmental problems [16]. Alum sludge contains lots of inorganic particles and residual aluminum hydroxide [17]. These inorganic particles will provide a good skeleton and friction and squeeze for crushing the sludge particles acting as physical conditioners. Aluminum hydrolysate and the residual PACl might implement the charge neutralization and adsorption bridging effect acting as chemical conditioner [18–20]. Therefore, PAM is also used in the process of sludge dewatering in the drinking water treatment plant; thus, the residual PAM in the alum sludge is also helpful for sludge dewatering [21]. Although co-treatment of alum sludge and sewage sludge has widely been studied, there has been relatively little research on the blended sludge dewatering mechanism when alum sludge mixed with sewage sludge as chemical conditioners and physical conditioners, and few of them used 3D-excitation-emission matrix (3D-EEM) to indicate the sludge dewatering performance. Compared to other analytical methods, the 3D-excitation-emission matrix (3DEEM) was more convenient. Furthermore, there has few literature to discuss the alum sludge to improve the sewage sludge dewaterability with centrifugation process, though centrifugal dewatering is one of the common methods in dewatering industry. In the literature [22], the researchers just discussed the filter press to improve the sewage sludge dewaterability with alum sludge, and it did not deal with the centrifugation process. In addition, the special centrifugal tube was designed and made for the experiments, to observe the dewatering experimental result more clearly, and analyze the dewatering experimental samples more accurately. The aim of this work is to: (1) investigate the effect of the blended sludge dewaterability with centrifugation process; (2) propose the dewatering mechanism of alum sludge
13
J Mater Cycles Waste Manag
mixed with sewage sludge as chemical conditioners and physical conditioners through scanning electron microscope (SEM), energy dispersive spectrometry (EDS), and 3D-excitation-emission matrix (3D-EEM); (3) estimate the feasibility of reducing the dewatering conditioners and the economy of co-dewatering. The results provide important insights for systematically understanding the dewatering mechanism of co-treatment and the technical and economic aspects of co-treatment of alum sludge and sewage sludge.
Materials and methods Materials In this experiment, the sewage sludge was taken from the secondary sedimentation tank of Qige wastewater treatment in Hangzhou city. The VSS/SS was approximately 75%, the pH value was 6.8–7.0, and the moisture content was about 98.5%, which was stored under room temperature. It was activated sludge and it would be ready for dewatering after adding PAM in the wastewater treatment plant (WWTP). All experiments were carried out in 2 days after sampling. The alum sludge was from a local drinking water treatment plant and the moisture content was 64%, which was dewatered in the water treatment plantby machinery. In this work, we did not carry out the alum sludge dewatering experiment. In the water treatment plant, PACl was used as the primary coagulant to purifying drinking water, and then the residual PACl and reaction product might deposit in thealum sludge. Besides, polyacrylamide (PAM), surfactants, are widely applied to improve the mechanical dewaterability of the sludge [23]. In this WTP, the dosage of PACl was 27 g/t water and the dosage of PAM was 0.21 g/t water. The finally alum sludge moisture content was about 64% and the pH value was about 6.9–7.1. The alum sludge color was yellowish-brown. The sludge was stored under room temperature. Inorganic phase may be different in various water treatment plants, according to the different drinking water source, such as river water, lake water, groundwater, which may contain the different inorganic particle. However, in drinking water treatment, in general, the purifying water process is composed of coagulation, sedimentation, filtration, disinfection, and it needs to add flocculant, such as PACl, aluminum sulfate, ferric chloride, or other chemical agents. Therefore, the alum sludge always contains certain inorganic particles and residual aluminum hydroxide, even residual PAM and PAM reaction product after dewatering. In this study, we just discussed the river water as drinking water source and it contained lots of inorganic particles, which was helpful for blended sludge dewatered. More
J Mater Cycles Waste Manag
detailed quantitative analysis might be conducted in the further research. Sludge centrifugal dewatering tube Centrifugal dewatering system included the conventional laboratory low-speed centrifuge (350 L × 370 W × 295 Hmm) with the maximum speed 5000 r/min and the special centrifugal tube (50 mL). The sludge samples were dewatered by the centrifuge about 15 min with 2000 rpm. The special centrifugal tube (115 mm × ϕ 30 mm, made in the lab) was divided into three parts and the dewatering sludge was sampled from Part II, and centrifugal water was obtained from Part III (Fig. 1). Analytical methods Sludge dewatering performance The specific resistance to filtration (SRF) is an important index to reflect the dewatering performance of sludge, and higher SRF value indicates poorer dewatering performance. SRF and moisture content were measured according to the literature [24]. All samples were performed duplicate.
manual operation instruction after dewatering.The main components of the sludge samples were tested with energy dispersive spectrometry (EDS) (EDAX, AMETEK) with condition under an accelerating voltage of 25 kV, tilt: 0.70, take-off: 33.97, ampT: 102.4, detector type: SUTW-Sapphire, resolution: 137.91, the dewatering sludge was sampled from Part II, and centrifugal water. To improve the observation effect and reduce the difficulty of operation, the sewage sludge for SEM observation was applied with gold electroplating. The 3D-excitation-emission matrix (3D-EEM) of clarifying supernatant in beaker (1 L) and centrifuge liquid obtained from Part III (Fig. 1) were conducted with F97 luminescence spectrophotometer (Shanghai Lengguang Technology Co. Ltd.). The supernatant was taken from the original sewage sludge and blended sludge (1 kg/kg of mixing ratio) after stiring for 10 min and standing for 15 min in the beaker, respectively. PTM voltage was 500 V, the emission interval was 1 nm, and the excitation interval was 10 nm. The emission and excitation wavelengths were varied in the between of 200 and 600 nm. The scan speed was set at 6000 nm/min. The 3D-EEM data were processed by origin 8.0. All samples were performed duplicate.
Process and analysis
Results and discussion
The alum sludge (64% of moisture content) was added to the sewage sludge (5 L) (99% of moisture content) which was original from the WWTPsecondary sedimentation tank with different dry weight ratio in experiments, and then stirred for 10 min until blended completely. The 1 kg/kg means 1 kg dry alum sludge and 1 kg dry sewage sludge blended together. The different sludge samples surface structure was scanned with scanning electron microscope (SEM) (EDAX, AMETEK). The SEM samples were performed under the
The specific resistance to filtration of blended sludge The SRF values of the original sewage sludge and blended sewage sludge (1 kg/kg) were showed under the different PAM dose proportions (Fig. 2). It was very obviously found that two groups SRF value decreased with the increase of PAM dosage content. At the beginning, without PAM, the SRF of the blended sludge and the sewage sludge were 1.27 × 1013 and 3.73 × 1013 m/kg, respectively. Then, under the same PAM dosage, the blended sludge SRF value was
Fig. 1 The device of centrifugal experiment
Injection sample 30cm Part I Centrifugalsludge Part II
Filter pore + Filter cloth Rubber band
Part III
Part II
Part I Part III
Centrifugal liquid
13
J Mater Cycles Waste Manag 4.5
sludge SRF value was down to 0.89 × 1013 m/kg even in the absence of PAM by centrifugal dewatering. The result showed that the alum sludge with the increasing dosage could gradually reduce the dosage of PAM and even eliminate the addition of PAM on the dewatering effect. The result was similar with the literature [16].
sewage sludge sewage sludge+1Kg/Kg alum sludge
SRF ×10 13 ( m /K g )
3.6
2.7
The moisture content of blended sludge after centrifugal dewatering
1.8
0.9
0.0
0
1
2
3
4
5
6
PAM dosage(g/Kg) Fig. 2 Change of sludge SRF with different dosages of PAM
4.5
Moisture content of dewatered sludge(%)
much lower than the other group SRF value. In the sewage sludge, with the PAM content increasing to 1.5 g/kg, the SRF value decreased obviously, but after PAM further increased, the effect to reduce the BRFvalue was not obvious.The same SRF trend appeared in the blended sewage sludge, after the PAM content increased. This result showed that the effect of alum sludge addition was more obvious to reduce the SRF value than the effect of PAM. Figure 3 showed the results of SRF after increasing the alum sludge dosage under the same PAM dosage (1.5 g/kg) addition. The SRF of sewage sludge decreased evidently as the increasing of alum sludge dosage addition. After the addition of alum sludge increased to 1 kg/kg, the reducing trend of SRFvalue slowed down, and both the SRF values were close to the same. When the ratio was 1:2, the blended
swedge sludge swedge sludge+1.5g/Kg PAM
2.7
13
SRF×10 (m/Kg)
3.6
1.8
0.9
0.0 0.0
0.5
1.0
1.5
2.0
2.5
alum sludge dosage(g/Kg) Fig. 3 Change of sludge SRF with different dosages of alum sludge
13
The moisture contents of sludge after centrifugal dewatering were determined to gain a further understanding with adding alum sludge or PAM dose in the sewage sludge. The change of moisture content of dewatered sludge with different PAM dosages was shown in Fig. 4. Without alum sludge and without PAM, the moisture content of sewage sludge was 90% after dewatering, and if it was no alum sludge, the moisture content of sewage sludge would decrease after added different proportions of PAM and the lowest moisture content was about 80%. While the moisture content of blended sludge (1 kg/kg alum sludge/sewage sludge) had obviously decreased with different proportions of PAM, and the lowest moisture content was only 62%, which almost nearly meet the landfill disposal requirements in China. To some extent, the addition of alum sludge in these wage sludge was more favorable for dewatering. In Fig. 5, as the increasing alum sludge dosage in the sewage, the moisture content of blended sludge dropped obviously from 90 to 58% after centrifugal dewatering. Under the blend ratio of 1 kg/kg of the alum sludge to sewage sludge, the moisture content was about 64%, but the effect of PAM addition was not obvious. This result indicated that the dewaterability of blended sludge became 100
sewage sludge sewage sludge+1Kg/Kg alum sludge
90
80
70
60
50
0
1
2
3
4
PAM dosage(g/Kg)
5
6
Fig. 4 Change of moisture content of dewatered sludge with different dosages of PAM
M o is tu r e c o n te n t o f d e w a te r e d s lu d g e (% )
J Mater Cycles Waste Manag 100
sewage sludge sewage sludge +1.5g/Kg PAM
90
80
70
60
50 0.0
0.5
1.0
1.5
2.0
2.5
alum sludge dosage(kg/kg)
Fig. 5 Change of moisture content of dewatered sludge with different dosages of alum sludge
better with the addition of alum sludge and there was no obvious change with the addition of PAM. Centrifugal dewatering mechanism of blended sludge Improving dewatering of sewage sludge blended with alum sludge The surface structure of the original sewage sludge, alum sludge, and blended sludge samples was scanned using scanning electron microscope (SEM) in Fig. 6. The microstructure of the original sludge sewage was sticky and dense shown in Fig. 6a, the surface of alum sludge was patchy shown in Fig. 6b, and the surface of blended sludge had rough and porosity structure shown in Fig. 6c, which could provide lots of outflow channels for free water when the blended sludge was dewatered. In this study, it is difficult to directly detect the concentration of inorganic particles (i.e., Al, Si, O etc.) in sludge which was helpful for the blended sewage sludge dewaterability. Therefore, energy dispersive spectrometry (EDS) was employed to detect the chemical composition of the sludge, which could reflect the variation of inorganic particles in sludge during the dewatering processes. The elements’ content distribution of three kinds of sludge was shown in Table 1: the original sewage sludge, alum sludge, and blended sludge, respectively. Table 1a showed that the C element had high proportions about 50% in the percentage of table elements, with small amount of Si element, which meant that the majority content of original sewage sludge was organic particles.While in Table 1b, the main amount of element contents was Si and Al and all of them accounted for 33%. It may conclude that the main coagulant
was PACl in this water treatment plant and there had more inorganic sand in alum sludge. The elements content distribution of blended sewage sludge was shown in Table 1c. After blended with alum sludge, the content of inorganic particles increased and both Al and Si contents accounted for 24%, which chemical composition was obvious different with the original sewage sludge. It suggests that the chemical interactions of alum sludge and sewage sludge would result in the increasing of inorganic particles in the blended sewage, which is more helpful for the blended sewage dewatering. Inorganic particles could make squeezing and provide outflow channels, while residual product of PACl had the effect on charge neutralization and adsorption bridging. It is inferred that the alum sludge acts as physical conditioner and chemical conditioner for sludge dewatering. Moreover, residual PAM is also helpful for sludge dewatering if PAM is added alum sludge for dewatering in WTP. Analysis of protein‑like particles fluorescence for centrifugal dewatering process In the sewage sludge, the microorganism can produce large amount of extracellular polymeric substances (EPS) and the proportion of EPS in total organic matter of activated sludge is roughly between 50–90% [25]. EPS contains a large number of aromatic structure and unsaturated fatty acids with different functional groups which have different fluorescence [26]. In process of centrifugal dewatering, inorganic particles (sand) in alum sludge would squeeze the blended sludge and then the sludge cell would break to produce a lot of different functional groups.The different functional groups have different fluorescence [27], and then the different types of EPS peak can be detected by 3D-EEM fluorescence spectra, such as protein-like particles fluorescence and so on [28]. Therefore, their specific fluorescence properties (protein-like particles) can be used as a standard to test the extent of cell damage. The protein-like particles fluorescence peak existed in excitation wavelength/emission wavelength = 320–400/400–480 nm. The fluorescence peak results of supernatant and centrifugal liquid were shown in Fig. 7a1–a7 and b 1–b7 at different times on 0, 1, 3, 5, 10, 15, and 20 min, respectively. The fluorescence peaks intensities of the protein-like particles were shown in Fig. 8. In Fig. 7a1 and b 1, the fluorescence intensity of proteinlike particles insupernatant was different between the sewage sludge and blended sludge. The fluorescence intensity of supernatant from blended sludge was obvious higher than that of sewage sludge. A supplementary experiment showed there is almost no fluorescence intensity in the alum sludge supernatant due to little organic matter in it. According to the increasing of protein-like particles
13
J Mater Cycles Waste Manag
Fig. 6 Microstructure of sewage sludge (a), alum sludge (b), blended sludge with ratios of 1 kg/kg (c) (a–c SEM images are from scanning electron microscopes and the magnification was 2000 and 5000)
in blended sludge supernatant, it was suggested there had produced chemical reactions between the alum sludge and sewage sludge due to the residual products of PACl in alum
13
sludge which had effect on increase of protein-like fluorescence intensity of supernatant.This process can be considered as the chemical conditioning for sludge.
J Mater Cycles Waste Manag Table 1 Elements content of the sewage sludge (a), alum sludge (b), and the blended sludge (c) detected with energy dispersive spectrum
Sewage sludge
Alum sludge
Blended sludge
(a)
(b)
(c)
Element
Weight%
Atomic%
Element
Weight%
Atomic%
Element
Weight%
Atomic%
C O Mg Al Si K Ca Fe
50.11 37.53 0.72 0.05 4.12 3.29 1.84 2.34
60.76 34.13 0.44 0.03 2.14 1.23 0.67 0.61
C O Mg Al Si K Ca Fe
13.79 43.86 1.10 10.76 22.45 2.54 0.86 4.64
21.65 51.67 0.86 7.51 15.11 1.23 0.41 1.56
C O Mg Al Si K Ca Fe
26.50 40.33 0.76 8.17 16.78 3.23 1.04 3.18
37.88 43.25 0.54 5.19 10.28 1.42 0.45 0.98
In Fig. 7a2–a7 and b2–b7, with centrifugal process, the fluorescence intensity in centrifugal liquid showed the same change trend, and the trend was more obvious in the blended sewage sludge due to the alum sludge. At the beginning of centrifugal process, both the fluorescence intensities decreased from 1 to 3 min (a2–a3, and b 2–b3). The decrease of fluorescence intensity (protein-like particles) showed that there was bigger gap between the sand particles and then it is hard to produce frictional interaction, so the main process was filtration function and more free water were released. Then from 5 to 10 min ( a4–a5, and b4–b5), the fluorescence intensity in centrifugal liquid was rapidly increased even over the supernatant, it suggested that the addition of alum sludge which contained inorganic particles provides friction and squeeze for crushing sludge particles even cell to release lots of protein-like particles through centrifugal press. Finally, the fluorescence intensity decreased again (a6–a7, and b6–b7), it may be concluded that there was no space for frictional interaction between the sand particles, and less protein-like organic particles were leaked out. This process is probable a physical conditioning for sludge dewatering. Hypothesis for centrifugal dewatering of blended sludge A schematic model was presented to interpretthe centrifugal dewatering process through addition of alum sludge in the sewage sludge. Before the centrifugal dewatering, after the alum sludge blended into sewage sludge, the residual products of PACl acted as chemical conditioning to charge neutralization and adsorb bridging in the blended sludge to make the sludge easier dewatering. Higher fluorescence intensity of proteinlike particles in clarifying supernatant from blended sludge proved occurring of chemical conditioning, which reflects destruction or solution of biomass. In process of centrifugal dewatering, inorganic particles (sand) acted as skeleton builders and squeeze the blended
sludge to improve the sludge dewatering. Higher fluorescence intensity of protein-like particles infiltered water through centrifuge reflected friction and squeeze between inorganic particles and biomass, which likes physical conditioning to improve dewatering. Final disposal options of blended sludge The final disposal options of the blended sludge would be landfilling and building material utilization, according to the experiment results. After the centrifugal dewatering, the lowest moisture content was only 58% in the blended sludge, which met the landfill disposal requirements in China (≤60%). In addition, it can be seen from Table 1 that it also contained large amount inorganic particles in the blended sludge, so the blended sludge could be used for building material utilization. Though the sludge incineration and land application of sewage sludge are the two frequently employed disposed methods, the calorific value and the contents of nutrient of the blended sludge are very low. Therefore, it was not suitable for incineration and land application.
Conclusions The goal of blended the two sludges was to improve the sewage sludge dewaterability and reduce the dewatering conditioners. In this work, alum sludge as recycling waste material, which contained inorganic particle and residual PACl and/or PAM, was obvious beneficial to improve sludge dewaterability when it added into sewage sludge. The SRF and the moisture content of the blended sludge were significantly decreased and the lowest moisture content was only 58% after centrifugal dewatering. The EDS results indicated that addition of alum sludge increased the content of residual product of PACl and inorganic particles in the blended sludge like Al and Si. The high protein-like
13
Fig. 7 Protein-like particles 3D-EEM fluorescence spectral of supernatent and centrifugal dewatering of the sewage sludge (a1–a7) and the blended sludge when blended ratios were 1 kg/kg (b1–b7) (the proteinlike particles fluorescence peaks are located in excitation wavelength/emission wavelength = 320–400/400–480 nm)
13
J Mater Cycles Waste Manag
J Mater Cycles Waste Manag 750
sewage sludge, no alum sludge sewage sludge, 1kg/kg alum sludge
700
Fluorescence (a.u.)
650 600 550 500 450 400 350 300 250 200
0
5
10
15
20
The centrifugal press time (min) Fig. 8 Change of protein-like particles fluorescence intensity of supernatant and centrifugaldewatering from sewage sludge and blended sludge at blended ratios 1 kg/kg when the excitation wavelength/emission wavelength is at 320/400 nm
particles fluorescence intensity in supernatant of blended indicated chemical conditioning of alum sludge. The higher protein-like particles fluorescence intensity occurred in centrifugal dewatering process indicated physical conditioning by inorganic sand from alum sludge. Therefore, it was technically feasible to add alum sludge in sewage sludge to improve the centrifugal dewaterability of blended sludge. And adding alum sludge can reduce the dosage of polymer and decrease the cost. Simultaneously, it also decreased risk for using polymer as PACl or PAM in the following waste sludge treatment. The final disposal options of the blended sludge would be landfilling and building material utilization, due to the large amount inorganic particles and low the calorific value and the contents of nutrient. Acknowledgements This work was supported by the National Natural Science Foundation of China (No. 51478433), Science and Technology Project of Zhejiang (No. 2010R50037), and Zhejiang Provincial Natural Science Foundation of China (No. LY17D030001).
References 1. Tsai W-T (2014) Analysis of municipal solid waste incineration plants for promoting power generation efficiency in Taiwan. J Mater Cycles Waste Manag 18(2):1–6 2. Sørensen PB, Hansen JA (1993) Extreme solid compressibility in biological sludge dewatering. Water Sci Technol 28:133–143 3. Qi Y, Thapa KB, Hoadley AF (2011) Application of filtration aids for improving sludge dewatering properties—a review. Chem Eng J 171:373–384 4. Saveyn H, Pauwels G, Timmerman R, Van der Meeren P (2005) Effect of polyelectrolyte conditioning on the enhanced
dewatering of activated sludge by application of an electric field during the expression phase. Water Res 39:3012–3020 5. Zhou J, Liu F, Pan C (2014) Effects of cationic polyacrylamide characteristics on sewage sludge dewatering and moisture evaporation. PloS one9:e98159 6. Wang J, Chen C, Gao Q, Li T, Zhu F (2012) Relationship between the characteristics of cationic polyacrylamide and sewage sludge dewatering performance in a full-scale plant. Proc Environ Sci 16:409–417 7. Sørensen B, Wakeman R (1996) Filtration characterisation and specific surface area measurement of activated sludge by rhodamine B adsorption. Water Res 30:115–121 8. Wu M, Wei C, Zhu R, Pan X, Wang Y (2009) Enhancement of the settling and dewatering properties of activated sludge by humus soil. In: Bioinformatics and biomedical engineering, 2009 ICBBE 2009 3rd International Conference. IEEE, pp 1–4 9. Lee J-E (2011) The effect of the addition of fly ash to municipal digested sludge on its electroosmotic dewatering. J Mater Cycles Waste Manag 13:259–263 10. Qi Y, Thapa KB, Hoadley AF (2011) Benefit of lignite as a filter aid for dewatering of digested sewage sludge demonstrated in pilot scale trials. Chem Eng J 166:504–510 11. Tunçal T (2011) Improving thermal dewatering characteristics of mechanically dewatered sludge: response surface analysis of combined lime-heat treatment. Water Environ Res 83:405–410 12. Lee D, Jing S, Lin Y (2001) Using seafood waste as sludge conditioners. Water Sci Technol 44:301–307 13. Nittami T, Uematsu K, Nabatame R, Kondo K, Takeda M, Matsumoto K (2015) Effect of compressibility of synthetic fibers as conditioning materials on dewatering of activated sludge. Chem Eng J 268:86–91 14. Zhang H, Yang J, Yu W, Luo S, Peng L, Shen X et al (2014) Mechanism of red mud combined with Fenton’s reagent in sewage sludge conditioning. Water Res 59:239–247 15. Chang G, Liu J, Lee D (2001) Co-conditioning and dewatering of chemical sludge and waste activated sludge. Water Res 35:786–794 16. Guan B, Yu J, Fu H, Guo M, Xu X (2012). Improvement of activated sludge dewaterability by mild thermal treatment in CaCl2 solution. Water Res 46:425–432 17. Neyens E, Baeyens J (2003) A review of thermal sludge pretreatment processes to improve dewaterability. J Hazard Mater 98:51–67 18. Taylor M, Elliott HA (2012) Influence of water treatment residuals on dewaterability of wastewater biosolids. Water Sci Technol 67:180–186 19. Peeters B, Dewil R, Vernimmen L, Van den Bogaert B, Smets IY (2013). Addition of polyaluminiumchloride (PACl) to waste activated sludge to mitigate the negative effects of its sticky phase in dewatering-drying operations. Water Res 47:3600–3609 20. Lai J, Liu J (2004) Co-conditioning and dewatering of alum sludge and waste activated sludge. Water Sci Technol 50:41–48 21. Vieira C, Margem J, Monteiro S (2008). Microstructural changes of clayey ceramic incorporated with filter sludge from water treatment plant. Matéria (Rio de Janeiro) 13:275–281 22. Li J, Liu L, Liu J, Ma T, Yan A, Ni Y (2016) Effect of adding alum sludge from water treatment plant on sewage sludge dewatering. J Environ Chem Eng 4:746–752 23. Luo H, Ning X-A, Liang X, Feng Y, Liu J (2013) Effects of sawdust-CPAM on textile dyeing sludge dewaterability and filter cake properties. Bioresour Technol 139:330–336 24. Kim KS, Sajjad M, Lee J, Park J, Jun T (2014) Variation of extracellular polymeric substances (EPS) and specific resistance to filtration in sludge granulation process to the change of influent organic loading rate. Desalination Water Treat 52:4376–4387
13
25. Jahn A, Nielsen PH (1998) Cell biomass and exopolymer composition in sewer biofilms. Water Sci Technol 37:17–24 26. Leenheer JA, Croué J-P (2003) Peer reviewed: character izing aquatic dissolved organic matter. Environ Sci Technol 37:18A–26A
13
J Mater Cycles Waste Manag 27. Baker A (2002) Fluorescence properties of some farm wastes: implications for water quality monitoring. Water Res 36:189–195 28. Li W-H, Sheng G-P, Liu X-W, Yu H-Q (2008) Characterizing the extracellular and intracellular fluorescent products of activated sludge in a sequencing batch reactor. Water Res 42:3173–3181