Suction Time Research Articles

Hybrid conditioning of ionic liquid coupling with H2SO4 to improve the dewatering performance of municipal sludge.

Municipal sludge generated from wastewater treatment plants can cause a serious environmental and economic burden. A novel hybrid conditioning strategy was developed to enhance the dewatering performance of sludge, employing 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4mim][CF3SO3]) treatment combined with H2SO4 acidification. Following conditioning, the capillary suction time ( ), the specific resistance of filtration (SRF), and moisture content of the treated sludge were decreased to 1.99 ± 0.24 (s·L/g TSS), 1.33 ± 0.05 (1012m/kg), and 72.01 ± 0.94%, respectively. The results were superior to those achieved with sludge treated solely by H2SO4 acidification or [C4mim][CF3SO3] alone. The biomacromolecules within the sludge flocs were dissolved by [C4mim][CF3SO3], while simultaneously, the microorganisms were inactivated. Consequently, the colloidal-like structures of the sludge flocs were destroyed. Additionally, the ionizable functional groups of the biomacromolecules were instantly protonated by the introduced H+ ions, and their negative charges were neutralized during the H2SO4 acidification process. The presence of H+ ions promoted the weakening of electrostatic repulsion between the sludge flocs. As a result, an enhancement of sludge dewaterability was obtained after treatment with [C4mim][CF3SO3] and H2SO4 acidification. The finding of the intensification mechanism of sludge dewaterability brought by hybrid treatment of acidification and [C4mim][CF3SO3] provides novel insights into the field of sludge disposal.

Simultaneous Environmental Waste Management through Deep Dewatering of Alum Sludge Using Waste-Derived Cellulose

To simultaneously solve problems in an eco-friendly manner, introducing a waste residual as a sustainable conditioner to aid alum sludge dewatering is suggested as a cradle-to-cradle form of waste management. In this regard, the superiority of deep dewatering alum sludge with a powdered wood chip composite residual as a novel conditioner was explored, whereby traditional conventional conditioners, i.e., polyelectrolytes and lime, were substituted with powdered wood chips. Initially, Fe3O4 was prepared at the nanoscale using a simple co-precipitation route. Next, wooden waste was chemically and thermally treated to attain cellulosic fine powder. Subsequently, the resultant wood powder and Fe3O4 nanoparticles were mixed at 50 wt % to attain a wood powder augmented with iron, and this conditioner was labeled nano-iron-cellulose (nIC-Conditioner). This material (nIC-Conditioner) was mixed with hydrogen peroxide to represent a dual oxidation and skeleton builder conditioning substance. Characterization of the resultant conditioner was carried out using transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) transmittance spectrum analysis. The feasibility of the experimental results revealed that the moisture content in the sludge cake was lower after conditioning, and the capillary suction time (CST) was reduced to 78% compared to that of raw alum sludge after 5 min of dewatering time. Moreover, the optimal system parameters, including nIC-Conditioner and H2O2 concentrations, as well as the working pH, were optimized, and optimal values were recorded at 1 g/L and 200 mg/L for nIC-Conditioner and H2O2, respectively, with a pH of 6.5. Additionally, scanning electron microscope (SEM) analyses of the sludge prior to and after conditioning were conducted to verify the change in sludge molecules due to this conditioning technique. The results of this study confirm the sustainability of an alum sludge and waste management facility.

Use of current automatic smoke evacuation system in flexible gastrointestinal endoscopy: Its feasibility and potential usefulness.

Flexible endoscopy does not have a system that can automatically evacuate surgical smoke generated in the gastrointestinal lumen. We aimed to investigate the feasibility and potential usefulness of automatic smoke evacuation systems in flexible endoscopy. [Bench] After surgical smoke generated in the stomach was evacuated by the evacuator, the degree of residual smoke and gastric luminal collapse were evaluated to optimize the evacuator settings. [Animal] Insufflation, suction, and total operation time to complete the protocol of 10 cauterizations of the gastric mucosa were measured in three groups: "manual suction only," "manual suction with automatic evacuation (50% force)," and "manual suction with automatic evacuation (70% force)." The stability of endoscopic visualization and operability was evaluated by 10 endoscopists blinded to those suction settings, and the number of manual suctions, insufflations, and total operation time were measured. [Bench] The degree of residual smoke and gastric luminal collapse were inversely correlated. [Animal] When the automatic evacuator was partially used, there was no difference in the insufflation time, but the suction time (vs 50%; p = 0.011, vs. 70%; p = 0.011) and total operation time (vs. 50%; p = 0.012, vs. 70%; p = 0.036) were significantly reduced compared to manual operation only. Furthermore, manual suction with automatic evacuation (50% force) significantly improved the stability of endoscopic visualization and operability compared to manual operation only (p = 0.041, p = 0.0085). The automatic smoke evacuation in flexible gastrointestinal endoscopy was potentially feasible and useful by improving the device setting.

Visualization of water transfer channel in sludge dewatering conditioned with skeleton builders by X-ray micro-computed tomography

Skeleton builders were normally deemed to improve the high porosity and newly-generated permeability of sludge cakes by building water transfer channel during high pressure filtration, thus enhancing sludge dewaterability. However, currently a direct visualization proof of water transfer channel was still lacking. This study provided the direct proof for visualizing water transfer channel in dewatered sludge cakes conditioned with a typical skeleton builder (i.e., phosphogypsum (PG)) by X-ray micro-computed tomography (micro-CT) for the first time. After the addition of PG, the pixel value and image luminance increased significantly, indicating the presence of high density substances from both two-dimensional (2D) cross section and three-dimensional (3D) reconstruction CT images. Moreover, the CT numbers showed strong and negative correlations with specific resistance to filtration (SRF) (R = − 0.99, p < 0.05), capillary suction time (CST) (regression coefficient (R) = − 0.87, probability (p) < 0.05), and water content of the dewatered sludge cake (R = − 0.99, p < 0.05), respectively. These results indicated that the X-ray micro-CT could be a potential technique for analyzing the water distribution in sludge samples conditioned with skeleton builders.

Treatment of polluted river water using potential bioflocculant produced by Klebsiella pneumonia UKD24.

Chemically enhanced primary treatment (CEPT) is a rapid wastewater treatment process involving treating wastewater with two chemical-aided processes, coagulation, and flocculation. In the present study, a natural extracellular polymeric substance flocculant (EPSBF) produced by Klebsiella pneumonia UKD24, a bacterium isolated from the sewage treatment plant, and a synthetic polyacrylamide anionic polymer flocculant (PAM) were evaluated to treat polluted river water. The synthetic PAM showed immediate turbidity reduction after agitation, while the EPSBF expressed a rapid decrease in optical density. After 20 min of the settling period, the EPSBF showed reduced rates of turbidity, optical density, and chemical oxygen demand at 74.14 ± 5.2%, 89.37 ± 0.76%, and 87.21 ± 0.73%, respectively, while PAM showed 67.08 ± 4%, 85.68 ± 2%, and 86.57 ± 2%, respectively. EPSBF treatment significantly improved the water quality parameters in terms of total dissolved solids, total suspended solids, conductivity, and oxidation-reduction potential than PAM treatment. However, the EPSBF has shown a more water-holding capacity and relatively weak flock formation, producing more sludge volume than PAM. Furthermore, though the sludge produced by the EPSBF treatment had a higher moisture content, it showed shorter capillary suction time (CST). In contrast, sludge formed in PAM treatment had lower moisture content, but it exhibited prolonged CST value indicating that PAM treatment sludge showed slow dewaterability.

Optimizing suction force in mechanical thrombectomy: Priming the aspiration tubing with air versus saline.

We sought to investigate how priming the tube between air versus air mixed with saline ex vivo influenced suction force. We examined how priming the tube influenced peak suction force and time to achieve peak suction force between both modalities. Using a Dwyer Instruments (Dwyer Instruments Inc., Michigan City, IN, USA), INC Digitial Pressure Gauge, we were able to connect a .072 inch aspiration catheter to a rotating hemostatic valve and to aspiration tubing. We recorded suction force measured in negative inches of Mercury (inHg) over 10 iterations between having the aspiration tube primed with air alone versus air mixed with saline. A test was used to compare results between both modalities. Priming the tube with air alone compared to air mixed with saline was found to have an increased average max suction force (-28.60 versus -28.20 in HG, p<0.01). We also identified a logarithmic curve of suction force across time in which time to maximal suction force was more prompt with air compared with air mixed with saline (13.8 seconds versus 21.60 seconds, p<0.01). Priming the tube with air compared to air mixed with saline suggests that not only is increased maximal suction force achieved, but also the time required to achieve maximal suction force is less. This data suggests against priming the aspiration tubing with saline and suggests that the first pass aspiration primed with air may have the greatest suction force.

Aeration pre-treatment role in improving the performance of bio-conditioning dewatering of food waste anaerobic digestate

Bio-conditioning dewatering followed by activated sludge process (BDAS) is a promising technology for purifying food waste anaerobic digestate (FWAD). However, the bio-conditioning dewatering efficiency is often affected by FWAD properties and ambient temperature. Here, we firstly reported that aeration pre-treatment of FWAD played an important role in improving the bio-conditioning dewatering performance of FWAD. The study found that the accumulated carbonate (CO32–) in FWAD severely affected the flocculation of Fe-containing flocculant formed in microbial fermentation liquor due to the competitive consumption of the flocculant by CO32–. The capillary suction time (CST) and specific resistance to filtration (SRF) of the bio-conditioned FWAD increased from initial 77.8 s and 2.0 × 1012 m/kg to 122.7 s and 3.4 × 1012 m/kg, respectively, within 1 day of aeration. Prolonged aeration pre-treatment of FWAD could reduce its CO32– concentration and total alkalinity. Additionally, the aeration pre-treatment simultaneously decreased the proportion of macromolecular organic matter that hindered dewatering and the content of total solids (TS) and hydrophilic protein-like substances in FWAD. After 20 days of aeration followed by bio-conditioning, the CST and SRF reduced to final 36.5 s and 2.3 × 1011 m/kg, respectively, indicating a substantial improvement in dewatering performance. Successive forced aeration combined with the addition of CaCl2 to eliminate adverse factors mainly CO32– was a feasible and cost-effective strategy to realize bio-conditioning dewatering of FWAD in less than 2 days and a lower reagents dose of bio-conditioning, which was helpful in the engineering application of the novel BDAS process for FWAD purification.

Ultrahigh pressure filtration dewatering of municipal sludge conditioned by steel slag in combination with Fe2+/ sodium persulfate

Municipal sludge treatment in urban contexts faces significant challenges, especially when dealing with sludge characterized by exceptionally high water content and organic content. This study investigates the application of sodium persulfate oxidation activated by ferrous ions (Fe2+/SPS) in conjunction with waste steel slag as a conditioning agent for municipal sludge, capillary suction time and specific resistance filtration experiments were conducted on conditioned sewage sludge, along with dewatering tests under ultrahigh pressure conditions. Additionally, to investigate the potential underlying mechanisms, Scanning Electron Microscopy analysis, Zeta potential measurements, and comprehensive sample analyses were performed. The research reveals substantial improvements in sludge dewatering performance when steel slag is combined with Fe2+/SPS treatment. This combined treatment introduces additional ferrous ions into the sludge, generating radicals that disrupt the structure of extracellular polymeric substances and cells within the sludge. Steel slag also acts as a skeleton builder material, creating larger drainage pathways within the sludge cake under ultrahigh pressure, enhancing permeability, and accelerating moisture release. This combined treatment method holds promise for achieving deep sludge dewatering, under ultrahigh filtration pressure, with water content reduced to below 40%. The study not only highlights the advantages of using steel slag in combination with Fe2+/SPS treatment for sludge dewatering but also provides insights into the underlying mechanisms. This comprehensive treatment method reduces the excessive use of ferrous ions and costs while significantly enhancing dewatering performance, offering a promising solution for municipal sludge treatment and management.

Effect of electrolytic zero-valent iron activated sodium hypochlorite on sludge dewatering performance.

Using electrolytic zero-valent iron-activated sodium hypochlorite (EZVI-NaClO) to pretreat sludge, the capillary suction time (CST) was utilized to evaluate sludge dewaterability. Ammonia nitrogen (NH4-N), dissolved phosphorus, and total phosphorus in the supernatant were used to analyze sludge disintegration. This approach aimed to evaluate the effectiveness of the pretreatment process and its impact on the sludge composition. The migration and transformation of extracellular polymeric substances (EPS), including dissolved EPS (S-EPS), loosely boundEPS, and tightly bound-EPS (TB-EPS), were analyzed by detecting protein and polysaccharide concentrations and three-dimensional fluorescence excitation-emission spectroscopy (3D-EEM). The sludge particle properties, including sludge viscosity and particle size, were also analyzed. The results suggested that the optimal pH value, NaClO dosage, current, and reaction time were 2, 100 mg/gDS (dry sludge), 0.2A, and 30 min, respectively, with a CST reduction of 43%. Protein and polysaccharide contents in TB-EPS were significantly reduced in the EZVI-NaClO group. Conversely, protein and polysaccharides contents in S-EPS increased, suggesting that EZVI-NaClO treatment could disrupt the EPS. Besides, the viscosity of the treated sludge decreased from 195.4 to 54.9 mPa·S, indicating that sludge fluidity became better. ZEVI-NaClO could enhance sludge dewaterability by destructing protein and polysaccharide structure and improving sludge hydrophobicity.

Combining sulfite and freezing/thawing pretreatment to simultaneously improves methanogenesis, dewaterability, and pathogen inactivation of waste activated sludge: Depicting sulfite migration during ice crystal growth

Harmless treatment of waste activated sludge (WAS) is the primary goal for sludge management while bioresource recovery is raising wide scholarly and industrial interest due to the abundant resource potential in WAS. This study employed sulfite and freezing/thawing to pretreat WAS for its versatility in simultaneously enhancing methane production, improving dewaterability, and inactivating pathogenic microorganisms. The addition of 100 mg S/L of sulfite and subsequent freezing/thawing significantly promoted the release of organics from a low organic-contained WAS (volatile solid/total solid = 0.4), leading to a substantial increase in methane production by 10.99 %. The combined pretreatment significantly reduced the capillary suction time of sludge by 77.24 % and effectively inactivated pathogenic microorganisms to below detectable levels. From a micro level, sulfur aggregation was observed around sludge particles, which can be attributed to the process of ice formation. During this process, sulfite was continuously transferred to the aqueous phase surrounding the particles where were froze even slower. Moreover, the formation of capillary water ice crystals further compromised the protective function of extracellular polymeric substances (EPS) on sludge cells. Economic, and environmental analyses suggest this combined sulfite and freezing/thawing pretreatment has a potential for efficient sludge treatment towards energy recovery and safe disposal with high environmental and economic value.

Unveiling the role of pore characteristics in sludge dewatering: Visualization by Nano-CT and micromodel study

The solid-liquid separation is an indispensable and primary link in the process of sludge treatment and disposal. The past research was focused primarily on the technique explorations of sludge dewatering and always disregarded the internal pore structure and water migration behavior in sludge. In this work, the real three-dimensional pore structure of sludge was obtained by Nano-CT. Based on this, a pore-scale heterogeneous sludge micromodel was firstly presented, and the water flooding experiment was carried out to visualize the water migration behavior. The results showed that the sludge structure transformed from sheet-like floc to microsphere particles, and then agglomerated into large globular granules during anaerobic ammonia oxidation. And the equivalent pore size increases from 342 μm to 617 μm, improving the sludge dewaterability characterized by capillary suction time (CST). The most significant implication of this work was revealing the critical role of invalid connected pore in sludge dewatering. Such pore was not contributed to fluid flow but the circulating vortex in it even induced energy dissipation, thus deteriorated the sludge dewaterability. This work may be helpful to understand the critical role of pore characteristic in water migration and shed light on the new dewatering techniques from the perspective of regulating sludge structure.

Experimental investigation on sludge conditioning and dewatering using an agricultural biomass coupled with resource recovery

In this study, the effect of modified areca husk fibre biochar (MAFB-AlCl3) on dairy sludge conditioning and dewatering along with raw and modified coconut shell biochar (MCSB-FeCl3) was investigated. Further, MgO impregnated biochars of areca husk fibre and coconut shells was carried out to evaluate the performance on phosphate recovery from the diary sludge. The enhancement in sludge dewatering with MAFB-AlCl3 were evaluated experimentally and significant reduction of capillary suction time (CST) (51.6 %), moisture content (18%), zeta potential (1.3 mV) and increased settleability (32.7%) were observed. The sludge conditioning parameters namely dosage (% of dry solids (DS)), rapid mixing time (RMT), slow mixing time (SMT) were optimized by response surface methodology for the modified biochars. Optimum CST (31.51 s) was obtained at dosage (50 % of DS), RMT (9.89 min) and SMT (17.23 min). Results of batch study for phosphate recovery by MgO impregnated biochars (MgB) was found to be 96.6 % and 100 % by MgB of areca husk fibre (MgAFB) and coconut shells (MgCSB) respectively. The morphological characteristics and elemental distribution using field emission scanning electron microscopy (FE-SEM) & energy dispersive X-ray spectroscopy (EDS) reveals the structural change in the sludge particles for the modified biochars as well as for sludge. Hence MAFB-AlCl3, MgAFB and MgCSB is proved to be suitable and an effective candidate for sludge conditioning and dewatering coupled with phosphate recovery in handling the diary sludge.

Effects of chitosan and rice husk powder on thermal hydrolysis-anaerobic digested sludge conditioning: Dewaterability and biogas slurry fertility

To enhance the dewaterability of anaerobic digested sludge and to make full use of the biogas slurry. This study set up five sludge conditioning methods: polymeric ferric sulfate, polymeric aluminum chloride, cationic polyacrylamide, chitosan, and chitosan combined with rice husk powder. Their effects on the dewaterability of thermal hydrolysis-anaerobic digested sludge, bacterial community, and biogas slurry fertility were studied to find a non-toxic and non-risk dewatering technology for the environment and biogas slurry. Compared with that of the control group, moisture content, normalization capillary suction time, and specific resistance to filtration were reduced by 12.8%, 97.7%, and 82.9%, respectively. Chitosan enlarges the sludge flocs and forms complexes with proteins, disrupting the structure of the extracellular polymeric substances, thereby exposing more hydrophobic groups and reducing the hydrophilicity of the sludge. The subsequent addition of rice husk powder enhances the adsorption of hydrophilic substances and provides a stronger drainage channel for the sludge. In addition, the biogas slurry obtained by this conditioning method used as a fertilizer increased the dry weight and fresh weight of corn seedlings by 59.3% and 91.0%, respectively. And the total chlorophyll content increased by 84.6%. Pearson's correlation analysis showed that chitosan and rice husk meal had no toxic effect on the biogas slurry compared to the other three flocculants. The results showed that the combined treatment of chitosan and rice husk powder resulted in the best dewaterability. Overall, chitosan combined with rice husk powder is a green dewatering technology with great potential for anaerobic digested sludge dewatering and biogas slurry recycling.

Effects of lime and polymer flocculants on consolidation behaviours of high-water content sludge

Vacuum preloading combined with flocculation has shown great potential for improving the dredged sludge’s dewatering and consolidation. To identify a suitable flocculant combined with vacuum preloading method, this study investigated the effects of various common flocculants on the sludge’s filtration properties and consolidation behaviors. The results indicated that dual-use of polymeric aluminium chloride (PAC) and polyacrylamide (PAM) had the most significant improvement on sludge’s filtration performance, as reflected by capillary suction time. In addition, a single dose of PAM had the most substantial improvement on the sludge’s compressibility. While, lime improved the sludge’s permeability the most. To predict the consolidation settlement of flocculated sludge during vacuum preloading, a method was proposed based on a small homemade vacuum preloading apparatus and the Taylor method. The influence of different flocculants on sludge properties was also analyzed based on their flocculation mechanisms and microstructure. Finally, an appropriate flocculant for the sludge in vacuum preloading projects was suggested in accordance with different project goals.

Ameliorating tannery sludge dewaterability by disintegration of extracellular biopolymers with FeCl3-MnSO4/oxalic acid/sodium percarbonate: Spectroscopic profiling of dissolved organic matter in sludge filtrate

Effectual sludge dewatering techniques are strongly desired by industrial wastewater treatment plants. In this work, we scrutinised the efficacy of various Fenton based complex mediated processes like ferric chloride (FeCl3)/oxalic acid (OA)/sodium percarbonate (SPC) (FOS), FS (without OA), manganese sulphate (MnSO4)/oxalic acid (OA)/sodium percarbonate (SPC) (MOS) and MS (without OA) for which capillary suction time (CST) was attained as follows: MS (204 s) < MOS (180 s) & FS (180 s) < FOS (174 s) at pH 3. This implied the role of chelating agent (OA) in improving sludge dewaterability by disintegrating Extracellular Polymeric Substances (EPS) and releasing converted free water from the sludge flocs. FTIR results of sludge samples revealed the higher release of aromaticity after treatment process. Presence of aromatic carboxylate compounds were confirmed by GC–MS analysis. A detailed inquisition on the dissolved organic matter (DOM) of filtrate samples using 3DEEM fluorescence methods like second derivative Accumulative Fluorescence Emission (AFE), Fluorescence Regional Integration (FRI) and UV–Visible spectroscopic method like multipeak Gaussian fitting were performed that signified Microbial Soluble Products.

Characterization of the dewaterability of excess aerobic granular sludge

Aerobic granular sludge technology has emerged as a promising wastewater treatment process. However, downstream granular sludge management framework is still challenging and lacks sufficient scientific coverage. This research aims to elucidate the dewatering characteristics of aerobic granular sludge compared to activated sludge. Several parameters, such as zeta potential, specific resistance to filtrate, capillary suction time, bound water content, and rheological behavior, were employed to obtain a comprehensive understanding of the dewatering capability of targeted sludge types. The results indicate that aerobic granular sludge has a higher demand for flocculant polymer than activated sludge (1.07 - 3.40 times). Additionally, aerobic granular sludge demonstrates higher resistance to filtrate (1.22 ± 0.09 - 6.59 ± 0.36 ×1011 m/kg) compared to activated sludge (2.93 ± 0.09 ×109 m/kg). The resistance to filtrate was shown to be positively associated with the average granules size. The usage of flocculant polymer significantly reduced the resistance to filtrate of all targeted samples. The bound water content of granular sludge (1.83 ± 0.37 - 4.31 ± 0.15 g/g TS) was higher than that of activated sludge (0.75 ± 0.13 g/g TS). According to the rheological data, aerobic granular sludge has a slightly higher apparent viscosity than activated sludge. The results of this study provide valuable insights into the potential implications of aerobic granular sludge dewatering at full-scale applications.

Hyperbranched polymer nanocomposite as a potential shale stabilizer in water-based drilling fluids for improving wellbore stability

Shale hydration has been a frequent and challenging technical problem causing wellbore instability in oil and gas drilling processes. The aim of this study is to design a novel hyperbranched polymer nanocomposite (HBPN) based on a synergistic strategy of physical plugging and chemical inhibition to improve wellbore stability. The inhibitive property of HBPN was comprehensively evaluated through the sodium montmorillonite (Na-MMT) plates immersion test, capillary suction time (CST) test, and shale hot-rolling recovery test. Results implied that HBPN presented better inhibition performance. The shale hydration rate was reduced to 0.03 in the presence of HBPN. Particularly, the shale hot-rolling recovery rate reached 80.54 % at 150 °C and presented long-term shale inhibition durability. It demonstrated excellent plugging performance in the artificial low permeability filter cakes plugging test, reaching a plugging efficiency of 42.45 % with the addition of 2.0 w/v% HBPN. The potential mechanism of action of HBPN was proposed through particle size distribution (PSD) measurement, Zeta (ζ) potential measurement, Fourier transform infrared spectroscopy (FTIR) analysis, X-ray diffraction (XRD) analysis, and scanning electron microscope (SEM) analysis. The coordination of electrostatic interaction and hydrogen bonding impelled a decrease in the ζ potential and interlayer spacing of Na-MMT. Meanwhile, HBPN could embed into formation pores and fractures to establish a tight plugging zone. This approach outlined herein might provide an avenue to strengthen wellbore stability for the drilling industry.

Aluminum speciation in polymerized aluminum chloride: Roles and chloride ion migration in sludge dewatering

Chemical conditioning emerges as a pivotal determinant in augmenting sludge dewatering performance. In the realm of frequently employed aluminum chloride polymer conditioners, the impact of hydroxyaluminum is noteworthy. Beyond influencing dewatering efficacy, it introduces chloride ions, precipitating a cascade of subsequent treatment challenges. In this study, we investigated the dewatering efficiency of coagulants with varying aluminum speciation contents. Notably, the coagulant predominantly composed of medium polymeric aluminum (Alb) demonstrated superiority at a dosage of 0.08 g Al/g TSS, exhibiting favorable outcomes in terms of capillary suction time and specific resistance to filtration, measured at 22.3 s and 4.02 × 1012 m−1/kg−1, respectively. These values were notably lower compared to those obtained with low-polymerization state aluminum (Ala) at 25.2 s and 6.04 × 1012 m−1/kg−1, as well as high polymorphic aluminum (Alc) at 25.8 s and 4.69 × 1012 m−1/kg−1. It was attributed to multifactor (high charge density, high protein conversion efficiency, distinct pore drainage structures of microchannels, etc.). The investigation underscored that the predominant elevation in chloride ion content within the sludge system was primarily attributed to the dosing of polyaluminum chloride. Furthermore, the subsequent application of coagulant aids, such as cationic polyacrylamides and CaO, significantly influenced the chloride ion content within the sludge cake, thereby modulating dewatering efficiency and the subsequent disposal of sludge. Therefore, strategically managing aluminum forms and coagulant aids can optimize sludge dewatering efficiency and subsequent disposal processes.

The role of microstructure of extracellular proteins in dewaterability of alkaline pretreatment sludge during bioleaching

Alkaline pre-treatment is known to enhance the acid production efficiency of sludge but adversely affects its dewatering performance. In this study, the improvement of sludge dewaterability by a novel bioleaching system with inoculating domesticated acidified sludge (AS) and its underlying mechanism were investigated. The results showed that although the addition of Fe2+ and the reduction of pH improved the dewatering performance of sludge, their effects were inferior to that of AS + Fe. The addition of AS and Fe2+ significantly reduced the specific resistance to filtration and capillary suction time of the sludge by 98.6 % and 95.5 %, respectively. This improvement in dewatering performance was achieved through the combined actions of bio-acidification, bio-oxidation, and bio-flocculation. Remarkably, under alkaline pH, microorganisms in AS remained active, leading to the formation of iron-based bioflocculants, along with a rapid pH decrease. These bioflocculants, in combination with protein (PN) in tightly bound extracellular polymeric substances (TB-EPS) through amide bonding, transformed TB-EPS from extractable to non-extractable form, reducing PN content from 12.1 mg g−1DS to 5.09 mg g−1DS and altering the protein's secondary structure. Consequently, the gel-like TB-EPS matrix effectively broke down, releasing cellular water and significantly enhancing sludge dewaterability.

Effect of predatory bacterial mixtures on biolysis of waste activated sludge to improve dewatering performance

ABSTRACTThe generation of surplus sludge during biological wastewater treatment has become a prevalent issue, necessitating the development of a dewatering approach that is efficient, economically feasible, and ecologically sound. Bdellovibrio-and-like-organisms (BALOs) are obligatory parasitic bacteria that prey on an array of bacteria. In this study, different BALO strains were isolated and purified from waste activited sludge (WAS). Anti-predation host strains were applied to screen the BALO strains with different host-range to minimize the overlap of the biolysis prey spectrum. In addition, the BALO strains with different host preferences were mixed for sludge biolysis treatment efficiency comparison. The results indicated that the capillary suction time and the bound water content in the WAS treated with the mixed BALOs were significantly decreased by 25.9% ± 1.7% and 5.2% ± 1.2%, respectively, compared to those treated with the single BALO strain. The soluble chemical oxygen demand concentration in the mixed BALOs treated group was increased by 31.2% ± 0.7% than that treated with the single strain. The findings indicate that the mixed strains used in the treatment process resulted in a notable enhancement of both sludge dewatering performance and lysis degree. In addition, the abundance of Proteobacteria treated with the BALO mixtures decreased by 69.1% than the single strain treated one which demonstrated that the BALO mixture expanded the sludge host lysis spectrum. This study revealed the different effects of single and mixed strains on sludge community structure, suggesting that the BALO host-range expansion is crucial to further improve sludge dewatering performances.