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Article

Dewaterability Enhancement of Anaerobic Sludge Using Polymeric Aluminum Chloride and Polyoxyethylene Alkyl Ether Surfactants

by
Eunhye Song
*,
Eunju Kim
,
Gyeong Woo Kim
,
Cheol Jin Jeong
,
Wonbae Lee
and
Seong Kuk Han
*
Bio Resource Recirculation Center, Institute for Advanced Engineering, Yongin 17180, Republic of Korea
*
Authors to whom correspondence should be addressed.
Water 2024, 16(16), 2303; https://doi.org/10.3390/w16162303
Submission received: 17 July 2024 / Revised: 12 August 2024 / Accepted: 14 August 2024 / Published: 15 August 2024
Browse Figures
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Abstract

:
The use of coagulants, such as ferric chloride hexahydrate, in wastewater treatment processes is known to induce pipe corrosion and to contribute to the discoloration of treated water. This study explores alternative approaches to sludge dewatering by evaluating the effectiveness of polymeric aluminum chloride (PAC) as a coagulant and polyoxyethylene alkyl ether (POAE) as a surfactant. The impacts of coagulation/flocculation were assessed using time to filtration (TTF) and a pressure filter press. The effects of certain coagulant and surfactant dosages were studied. The inputs were in the range of 105–1750 mg/L for PAC and 28–152 mg/L for POAE, which were determined based on zeta potential (ZP) measurements. The optimal concentrations were 876 mg/L for PAC and 114 mg/L for POAE, resulting in a TTF of less than 1 min. Moreover, the effect of pH on anaerobic sludge dewaterability was investigated. At a low pH below 8, the ZP reached the maximum value, and a higher pH resulted in a reduction in ZP. Under low-pH adjustments, it was observed that the dewatering performance of the POAE surfactant improved more significantly than that of the PAC coagulant. In addition, the effect of pressure was analyzed using a pressure filter under conditions favoring POAE, with relatively lower dosages and greater cost-effectiveness. In order to evaluate the solubility of organic matter under pressurized conditions, the filtrate’s removal efficiency, chemical oxygen demand (COD), and total phosphorus (TP) were investigated. Solubilization did not occur at an increased pressure of around 10 bars. The findings presented in this study provide technical assistance for sludge treatment.

1. Introduction

South Korea generates 4.22 million tons of sewage per year, marking a 71.7% increase over the past decade [1]. Sludge processing costs account for 40–60% of the operating expenses of sewage treatment plants [2,3]. As the volume of generated sewage sludge continues to rise annually, local governments are incurring significant expenses for its management.
Sludge treatment typically consists of unit operations such as thickening, digestion, and dewatering. The final dewatered sludge cake, with a moisture content of approximately 84%, results in a volume reduction of 75–87% compared to the pre-dewatering sludge volume. This facilitates its handling and lowers transportation and processing costs [4,5]. However, the high moisture content of the dewatered cake accounts for about 70% of the total sludge disposal costs [6]; thus, reducing this moisture content is a crucial issue [7].
Due to high moisture of sludge, its management remains a significant technical challenge [8,9,10]. Reducing bound water is critical to enhancing sludge dewaterability [11,12]. Therefore, various pretreatment methods, including physical, chemical, and biological approaches, have been explored to improve sludge dewatering efficiency [10,13,14,15,16].
Unlike drying and incineration, filter press dewatering is known to be an energy-saving method. However, conventional mechanical dewatering processes are insufficient to effectively remove bound water within sludge flocs or reduce sludge moisture content [17,18,19]. Thus, chemical coagulation/flocculation treatment using ferric chloride or lime is required as a preconditioning process [20,21]. Colloidal particles in the sludge, which do not readily settle, are difficult to separate using mechanical pressure alone due to increased filtration resistance and clogging of the filter media pores as the particle size decreases [22,23]. Most sewage treatment plants predominantly employ chemical treatments using organic and inorganic coagulants.
In this study, we analyzed the impact of adding coagulants and surfactants as pretreatment methods, as they are the most common chemical approaches used in sludge dewatering, given their cost and efficiency [24]. One such approach is coagulation/flocculation in which small colloidal particles within the sludge form large flocs and dense cakes, thereby enhancing sedimentation and dewatering performance [24,25]. During coagulation, small colloidal particles suspended in water become destabilized after the addition of coagulants with opposite charges, reducing their surface charge and leading to aggregation and subsequent sedimentation [26,27,28].
The efficiency of coagulation/flocculation heavily depends on the chosen coagulants/flocculants, which perform differently due to their distinct structural characteristics, such as charge properties, ionic nature, specific functional groups, and molecular weight [26,27,28]. Based on the effects of coagulation/flocculation, charge neutralization and bridging are two widely recognized mechanisms [26,28,29].
Traditional coagulants such as aluminum sulfate, ferric chloride, and polymeric aluminum chloride (PAC) are primarily used owing to the predominantly negatively charged surfaces of most insoluble suspended solids in water. These trivalent metal inorganic salts achieve high charge neutralization effects based on the Derjaguin, Landau, Verway, and Overbeek (DLVO) theory and the diffuse double-layer model [30,31].
Surfactants adsorb onto the solid–liquid interface, enhancing solubility and reducing surface tension. Due to these characteristics, surfactants are extensively used across nearly all industries, including oil, cosmetics, paint, dye, and textiles, particularly for improving sludge treatment effects [32]. When used as a pretreatment in the sludge dewatering process, surfactants can neutralize the negative charge on the sludge surface. Consequently, this weakens the bonds between loosely bound extracellular polymeric substances (LB-EPSs) and tightly bound extracellular polymeric substances (TB-EPSs) in the sludge flocs, thereby promoting the substantial dissolution of extracellular polymeric substances (EPSs), primarily proteins and polysaccharides, from the sludge. Subsequently, the bound water associated with EPSs released from the sludge floc surface enters the sludge liquid phase [33]. Additionally, LB-EPSs and TB-EPSs are transformed into soluble EPSs due to their high hydration capability. The interstitial water trapped within the sludge flocs and the water retained inside the sludge are also released due to the disruption of the floc structure. All these factors collectively contribute to the release of bound water, further improving sludge dewaterability [34].
In this study, we analyzed the effect of inorganic coagulants, such as PAC and polyoxyethylene alkyl ether (POAE) nonionic surfactants, on anaerobic sludge as alternatives to ferric chloride hexahydrate for the filter press dewatering process on anaerobic sludge. Ferric chloride hexahydrate is effective for phosphorus removal because it can prevent the volatilization of hydrogen sulfide during anaerobic digestion. However, ferrates are highly corrosive acidic liquids, and chloride ions contribute to the increased corrosivity of water [8]. This leads to corrosion issues in pipelines, storage tanks, and pumps in the sewage treatment plant and can also cause coloration issues in the treated water [35]. The dewatering characteristics of anaerobic sludge were assessed by comparing the dosages of coagulants and surfactants and their effects at different pH levels through TTF analysis. Additionally, the impact of POAE dosages on the filter press process was studied to analyze the dewatering characteristics of anaerobic sludge under pressurized conditions. Moreover, the filtrates produced by the filter press were analyzed for their chemical oxygen demand (COD) and total phosphorus (TP) to determine the environmental impact of the filtrate under pressurized conditions. The influence of PAC and POAE on the sludge dewatering process was analyzed to provide technical support for sludge treatment.

2. Materials and Methods

2.1. Materials

Anaerobic sludge was collected from the Seoul branch of a wastewater treatment plant (WWTP), South Korea, and its age was between 15 and 20 days. The sampled sludge was refrigerated within 2 days and stored at 4 °C. The properties of the raw sludge are shown in Table 1.

2.2. Dewaterability Analysis of Anaerobic Sludge

Figure 1 illustrates a schematic diagram depicting the process of dewaterability analysis for anaerobic sludge using a coagulant and a surfactant. Overall, the amounts of coagulant and surfactant were determined based on the zeta potential (ZP), and then the optimal amount was settled on via TTF results. Finally, the dewaterability of the anaerobic sludge and the environmental impact of the filtrate were analyzed under pressurized conditions.

2.2.1. Chemical Pretreatment for Anaerobic Sludge Dewatering

Commercial PAC (Hoimyung waterzen, Gumi, Republic of Korea) was utilized as the coagulant. Additionally, a nonionic surfactant, POAE (Solenis, Wilmington, DE, USA), was used. The characteristics of these agents are presented in Table 2.

2.2.2. Time to Filtration

Time to filtration (TTF) is commonly utilized for the evaluation of sludge dewaterability [36,37]. In this study, TTF was measured using the apparatus shown in Figure 2. The experiments were performed using 100 mL of anaerobic sludge. The samples were filtered through 5 µm filter paper (Hyundai micro, No 20, Seoul, Republic of Korea) in a 110 mm standard Buchner funnel, and vacuum suction was applied. The time taken to collect 50 mL of the filtrate was recorded. Replicate experiments were conducted to assess reproducibility.

2.2.3. Pressure Filter Press

In this study, a 1 L lab-scale filter press was used to analyze the effect of pressure on the anaerobic sludge dewatering process, as shown in Figure 3. The anaerobic sludge was continuously fed into the filter press using a micro gear pump (Leadfluid, CT300S, Baoding, China). The sludge was pressurized up to 10 bar using a hydraulic cylinder while the filtrate was simultaneously discharged through a 5 µm filter cloth (Daehanfilter, Chungju, Republic of Korea). The pressure in the filter press was recorded in real time to analyze the dewatering performance. The filtration rate was analyzed through the weight of the discharged filtrate. The experiment was repeated to verify its reproducibility.

3. Results

3.1. Dewatering Capability Analysis of Anaerobic Sludge with PAC as Coagulant

Coagulant dosage is one of the most critical factors influencing the coagulation/flocculation process in sludge dewatering. An optimal dosage can be identified by considering both dewatering efficiency and cost-effectiveness. Insufficient or low dosages of coagulants/flocculants lead to weak charge neutralization and bridging effects. Conversely, excessive dosages can cause sludge particles to be enveloped by coagulants/flocculants, leading to the restabilization of floc suspension stability, known as the restabilization effect [29,38].
The effects of various PAC coagulant dosages were investigated for their anaerobic sludge dewatering characteristics. The PAC dosages varied from 105 to 1794 mg/L, as shown in Table 3.
The dosage was adjusted according to ZP measurements, and the results are shown in Figure 4. The ZP increased as the dosage of PAC increased, ranging from −35.65 mV to −33.29 mV, and −15.05 mV, exhibiting a maximum increase of 54.76%. It was observed that the increase in coagulant dosage resulted in the neutralization of negative charge on the sludge surface. Such a tendency is coincident with other findings [39].
ZP represents the surface electrical characteristics of colloidal particles in a solution. As the absolute value of ZP increases, coagulation does not occur, owing to an increase in electrostatic repulsion and a decrease in the interaction between particles; ZP values closer to zero facilitate significant coagulation [11]. Therefore, ZP could be used as an indicator of the stability of particles in a solution and the efficiency of the coagulation process in water treatment [40].
The time taken for the filtrate to be discharged was measured at intervals of 10 mL within the range of 10 to 50 mL, as shown in Figure 5. As the dosage of PAC increased from 105 mg/L to 1750 mg/L, the TTF decreased from 1008 s to 15 s, indicating a reduction of 98.51%.
The hindrance factors of the filtrate permeating through the filter cloth can be broadly categorized as membrane resistance, cake-layer resistance, and internal fouling resistance [41]. In this study, internal fouling resistance can be disregarded, since a new filter cloth was utilized in all experimental conditions.
The changes in the flux of the filtrate with the filtration time are presented in Figure 6a. As PAC dosages increased, the flux increased from 0.13 to 1.89 L/m2·h, and the time to achieve maximum flux decreased significantly from 30 to 3 s. These findings indicate that an increase in PAC dosage results in a decrease in filter resistance, which is similar to previous findings [42]. The filtration rates corresponding to the volumes of the filtrate are shown in Figure 6b. With a dosage of PAC ranging from 105 to 876 mg/L, when 10% of the sludge volume was discharged, the resistance caused by cake formation led to a reduction in speed. The maximum filtrate discharge rate per unit time was 0.33 to 1.66 mL/s. At a PAC dosage of 1794 mg/L, cake resistance was observed once 20% of the sludge volume was discharged. The filtration rate per unit time reached 10.00 mL/s, which is 16.67 times higher than the minimum speed. Based on previous studies [36,43], the optimal total time to filtration (TTF) value is approximately 70 s. In this work, the optimal PAC dosage was determined to be over 876 mg/L, at which the maximum flux was 0.63 L/m3·h, and the highest speed was 1.67 m/s.

3.2. Dewatering Capability Analysis of Anaerobic Sludge with POAE as Surfactant

Table 4 presents the dosage of the surfactant POAE, which varied from 28 to 151 mg/L. The effects of various POAE dosages and their anaerobic sludge dewatering characteristics were investigated.
The influence of surfactant dosage on ZP is shown in Figure 7. As the dosage of POAE increased, ZP increased from −35.65 mV to −33.09 mV–−23.38 mV. Compared to PAC conditions, POAE was found to be more effective in increasing ZP with relatively lower coagulant dosages.
The TTF profile of the anaerobic sludge with different dosages of POAE is depicted in Figure 8. As the dosage increased, the TTF decreased from 763 s to 26 s, representing a maximum reduction of 96.59%. This trend was found to be similar to the results observed under the same conditions using PAC.
Figure 9a presents the flux with dosages of POAE as a function of filtration time. With increasing POAE dosages, the maximum flux increased significantly from 0.20 to 1.89 L/m2·h. The time to reach maximum flux decreased from 19 s to 2 s. The change in filtration rate with increasing POAE dosage is shown in Figure 9b. Under POAE in the 28 to 151 mg/L range, the maximum filtration rates occurred when 10% of the sludge volume was discharged. As the POAE dosage increased, the maximum filtration rate increased from 0.53 to 5.00 mL/s. Based on a TTF of approximately 70 s, the optimal POAE dosage was determined to be over 114 mg/L, at which the maximum flux value was 1.26 L/m3·h and the maximum speed reached 3.33 m/s.

3.3. Dewatering Capability Analysis of Anaerobic Sludge with pH

pH conditions are a critical factor in the sludge dewatering process [44]. Dewatering efficiency varies with pH levels during coagulant treatment, primarily due to the increased negative charge on colloidal particles at higher pH [45,46]. Furthermore, pH influences the solubility and precipitation forms of coagulants [47]. Variations in pH also disturb cell walls, releasing intracellular substances and altering the solubility of EPSs [15,48]. Based on previous results, low-pH conditions exhibit a lower specific resistance compared to high-pH conditions [49]. Therefore, the ZP of sludge was measured after adjusting the pH, as depicted in Figure 10. The pH was adjusted using 2M NaOH and 2M H2SO4 based on the raw anaerobic sludge’s initial pH of 8.12. It was observed that an increase in pH led to a decrease in ZP, whereas a decrease in pH resulted in an increase in ZP.
The effects of the PAC coagulant and POAE surfactant dosages on pH are shown in Figure 11a,b. The input amounts of PAC and POAE were the same as those previously indicated in Section 3.1 and Section 3.2. As the PAC increased, the pH decreased from 8.12 to 7.80–6.80, exhibiting a decrease of up to 16.25% compared to untreated sludge, as shown in Figure 11a. Similarly, as the POAE increased, the pH decreased from 8.12 to 8.03–7.99 as the surfactant dosage increased, representing a 2.68% decrease compared to the pH of the raw sludge, as shown in Figure 11b. Overall, the extent of the decline in the coagulant’s pH was higher than that of the surfactant. Due to the hydrolysis of the PAC, the pH level of the sludge decreased with the addition of PAC, a finding similar to the results described in previous studies [50,51].
The conditions with a TTF of approximately 70 s, a PAC concentration of 876 mg/L, and a POAE concentration of 114 mg/L were selected to investigate the changes in coagulation characteristics according to pH. The effects of pH on the TTF of anaerobic sludge with PAC and POAE are presented in Figure 12. Compared to the unadjusted condition of pH 8.12, as the pH increased to 9 and 10, the TTF increased to 386 s and 1399 s, respectively, at a PAC dose of 876 mg/L and increased to 658 s and 2395 s at a POAE dose of 114 mg/L, indicating a deterioration in dewatering performance. As the pH decreased to 7, the TTF decreased to 74 s for PAC and 26 s for POAE, showing an improvement in dewatering performance. Thus, it was confirmed that the dewatering performance of POAE was more significantly affected by pH changes than that of PAC.

3.4. Evaluation of Anaerobic Sludge Dewatering Capability at High Pressure

The effect of pressure, a known factor influencing the dewaterability of sludge, was evaluated using a pressure filter press [52]. Upon comparing the dewatering performance of the previously assessed PAC coagulant and POAE surfactant, POAE demonstrated superior dewatering efficiency at a lower dosage. Consequently, the influence of pressure on dewatering efficiency was further analyzed using POAE. Surfactant amounts below the optimal TTF conditions mentioned earlier were selected to verify the improvement in dewatering performance with the application of pressure. The anaerobic sludge was prepared using POAE at 76 mg/L, which resulted in a TTF of 143 s. The effects of pressure on sludge dewaterability are presented in Figure 13, showing a change in the weight of the filtrate and the pressure profile within the filter press. A total of 100.4 g of filtrate, corresponding to 20.16% of the input anaerobic sludge, was discharged during the 16th minute. The pressure was measured at 8.8 bar one minute after pressurization and subsequently decreased to between 8.3 and 8.1 bar.
Filtrate flux is shown in Figure 14. A maximum rate of 0.51 m3/m2·h was observed 5 s after pressurization. Thereafter, it gradually decreased and measured at between 0.038 and 0.39 m3/m2·h. The average filtrate flux rate was found to be 0.06 m3/m2·h except for the maximum value.
A pressurized dewatering experiment was conducted at a POAE surfactant dose of 114 mg/L, at which the TTF was observed to be 73 s. The weight of the discharged filtrate and the pressure inside the reactor over time are presented in Figure 15. After the dewatering process, 445.13 g of the filtrate, corresponding to 89.34% of the anaerobic digested sludge, was discharged, confirming an improvement in dewatering efficiency compared to the 76 mg/L POAE condition. The pressure inside the reactor reached a maximum of 9.1 bar one second after pressurization and subsequently decreased to between 9.0 and 8.0 bar.
The filtrate flux under the 114 mg/L POAE condition is shown in Figure 16. A maximum rate of 0.72 m3/m2·h was observed 20 s after pressurization. Excluding the maximum rate, the filtration rate ranged from 0.28 to 0.71 m3/m2·h. The average rate, excluding the maximum value, was 0.28 m3/m2·h. Compared to the 76 mg/L POAE condition, the maximum rate increased by 29.17%, and the average rate improved by 366.67%, indicating an overall enhancement in speed.
The moisture contents of the dewatered cake and the filtrate COD and TP were analyzed to evaluate the reduction rate and the effect of wastewater treatment load under pressurization conditions, as listed in Table 5.
The moisture content of the anaerobic sludge decreased from 96.7% to 95.3% and 72.7% under POAE dosages of 76 mg/L and 114 mg/L, respectively. Consequently, the anaerobic sludge reduction rates were calculated to be 19.07% and 87.59%, respectively. The sludge reduction rate was derived using Equation (1).
S l u d g e r e d u c t i o n r a t e = ( W S G − W D C ) ( W S G ) × 100
where WSG is the weight of the sludge input into the dewatering process, and WDC is the weight of the dewatered cake.
Under pressurized conditions with surfactant treatment, the COD decreased from 39,200 mg/L to 1440 mg/L and 440 mg/L. Consequently, the COD removal rates were 96.33% and 98.88%, respectively. The TP content decreased from 130 mg/L to 32.3 mg/L and 0.5 mg/L, and the removal rates were 75.15% and 99.62%, respectively, demonstrating a proportional relationship with dewatering efficiency. It was also confirmed that the solubilization effects of COD and TP were not observed under pressurized conditions.

4. Conclusions

This study investigated the effects of polymeric aluminum chloride (PAC) and polyoxyethylene alkyl ether (POAE) on the anaerobic sludge dewatering process. The aim was to find a replacement for ferric chloride hexahydrate, which causes pipe corrosion and leads to the discoloration of treated water. Based on zeta potential (ZP) measurements, PAC was dosed in the range of 105–1750 mg/L, while POAE was dosed in the range of 28–152 mg/L. Based on a TTF of approximately 70 s, the optimal PAC dosage was determined to be over 876 mg/L, at which the maximum flux was 0.63 L/m3·h and the highest speed was 1.67 m/s. In addition, the optimal POAE dosage was determined to be over 114 mg/L, at which the maximum flux value was 1.26 L/m3·h and the maximum speed reached 3.33 m/s. The pH of anaerobic sludge had significant effects on sludge dewatering. The ZP decreased at pH levels above 9, while it increased at a lower pH of 7. As the PAC dosage increased, the pH decreased from 8.12 to 7.80–6.80, with a reduction rate of up to 16.82%. Under POAE conditions, the pH decreased from 8.12 to 8.01–7.99, a decrease of up to 1.60%. For both PAC and POAE, the TTF increased at a pH above 9. When the pH decreased to 7, only the TTF for POAE decreased, indicating improved dewatering efficiency. It was found that POAE had a greater impact on dewatering efficiency with pH control compared to PAC. The dewatering rate and efficiency were analyzed using a pressurized filter press under POAE conditions, showing superior dewatering efficiency at relatively low dosages of POAE compared to PAC. At a POAE concentration of 114 mg/L, the maximum filtration rate was 0.72 m3/m2·h, and the sludge reduction rate was confirmed to be 87.59%. Additionally, the removal rates for COD and TP were 98.88% and 99.62%, respectively. Solubilization was not observed under pressurized conditions. The findings of this study provide valuable insights for optimizing sludge treatment processes, offering a viable alternative to traditional ferric chloride-based methods.

Author Contributions

Conceptualization—E.S.; methodology—E.S. and E.K.; validation—E.S. and S.K.H.; formal analysis—E.S. and G.W.K.; investigation—C.J.J. and E.S.; resources—S.K.H., W.L., and E.S.; data curation—W.L. and E.S.; writing and original draft preparation—E.S.; writing, review, and editing—E.S.; supervision—S.K.H.; project administration—S.K.H. and W.L. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by Water and Wastewater Innovation Technology Development Project (2021002690009) funded by the Korea Environmental Industry & Technology Institute (KEITI) and the Ministry of Environment (ME) of the Republic of Korea (No. 1485019355), and the Technology Innovation Program (20018186) funded by the Korea Planning & Evaluation Institute of Industrial Technology (KEIT) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 1415184562).

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

References

  1. Ministry of Environment. 2020 Wastewater Statistics. Available online: https://me.go.kr/home/web/policy_data/read.do?pagerOffset=0&maxPageItems=10&maxIndexPages=10&searchKey=&searchValue=&menuId=10264&orgCd=&condition.toInpYmd=null&condition.code=A5&condition.fromInpYmd=null&condition.orderSeqId=6430&condition.rnSeq=110&condition.deleteYn=N&condition.deptNm=null&seq=7809 (accessed on 9 April 2024).
  2. Guo, W.-Q.; Yang, S.-S.; Xiang, W.-S.; Wang, X.-J.; Ren, N.-Q. Minimization of excess sludge production by in-situ activated sludge treatment processes—A comprehensive review. Biotechnol. Adv. 2013, 31, 1386–1396. [Google Scholar] [CrossRef] [PubMed]
  3. Qi, Y.; Wang, Z.; Jiang, P.; Guan, Y.; Wang, L.; Mei, L.; Zhou, A.; Hou, H.; Xu, H. Test and analysis of sludge dewatering with a vacuum negative pressure load at the bottom of full section. Adv. Civ. Eng. 2020, 2020, 8840043. [Google Scholar] [CrossRef]
  4. Fan, J.; Chen, Q.; Li, J.; Wang, D.; Zheng, R.; Gu, Q.; Zhang, Y. Preparation and dewatering property of two sludge conditioners chitosan/AM/AA and chitosan/AM/AA/DMDAAC. J. Polym. Environ. 2019, 27, 275–285. [Google Scholar] [CrossRef]
  5. Nan, S.; Jia, Y. Experimental research of sludge dewatering by vacuum filtration. J. Zhengzhou Univ. 2003, 35, 83–85. [Google Scholar]
  6. Lee, D.J.; Lee, S.Y.; Kwon, Y.H.; Cho, Y.A.; Bae, J.S. A study on environmental and economic analysis for each treatment of sewage sludge (II): Results of economic analysis. J. Korea Org. Resour. Recycl. Assoc. 2016, 24, 15–29. [Google Scholar]
  7. Wu, B.; Dai, X.; Chai, X. Critical review on dewatering of sewage sludge: Influential mechanism, conditioning technologies and implications to sludge re-utilizations. Water Res. 2020, 180, 115912. [Google Scholar] [CrossRef] [PubMed]
  8. Bennamoun, L. Solar drying of wastewater sludge: A review. Renew. Sustain. Energy Rev. 2012, 16, 1061–1073. [Google Scholar] [CrossRef]
  9. Zhang, W.; Cao, B.; Wang, D.; Ma, T.; Xia, H.; Yu, D. Influence of wastewater sludge treatment using combined peroxyacetic acid oxidation and inorganic coagulants re-flocculation on characteristics of extracellular polymeric substances (EPS). Water Res. 2016, 88, 728–739. [Google Scholar] [CrossRef] [PubMed]
  10. Zhang, W.; Yang, P.; Yang, X.; Chen, Z.; Wang, D. Insights into the respective role of acidification and oxidation for enhancing anaerobic digested sludge dewatering performance with Fenton process. Bioresour. Technol. 2015, 181, 247–253. [Google Scholar] [CrossRef] [PubMed]
  11. Li, Y.; Yuan, X.; Wu, Z.; Wang, H.; Xiao, Z.; Wu, Y.; Wang, H.; Xiao, Z.; Wu, Y.; Chen, W.; et al. Enhancing the sludge dewaterability by electrolysis/electrocoagulation combined with zero-valent iron activated persulfate process. Chem. Eng. J. 2016, 303, 636–645. [Google Scholar] [CrossRef]
  12. Qi, Y.; Thapa, K.B.; Hoadley, A.F. Application of filtration aids for improving sludge dewatering properties—A review. Chem. Eng. J. 2011, 171, 373–384. [Google Scholar] [CrossRef]
  13. Dhar, B.R.; Nakhla, G.; Ray, M.B. Techno-economic evaluation of ultrasound and thermal pretreatments for enhanced anaerobic digestion of municipal waste activated sludge. Waste Manag. 2012, 32, 542–549. [Google Scholar] [CrossRef] [PubMed]
  14. Liu, J.; Yu, D.; Zhang, J.; Yang, M.; Wang, Y.; Wei, Y.; Tong, J. Rheological properties of sewage sludge during enhanced anaerobic digestion with microwave-H2O2 pretreatment. Water Res. 2016, 98, 98–108. [Google Scholar] [CrossRef] [PubMed]
  15. Ruiz-Hernando, M.; Simón, F.X.; Labanda, J.; Llorens, J. Effect of ultrasound, thermal and alkali treatments on the rheological profile and water distribution of waste activated sludge. Chem. Eng. J. 2014, 255, 14–22. [Google Scholar] [CrossRef]
  16. Zhen, G.Y.; Lu, X.Q.; Li, Y.Y.; Zhao, Y.C. Innovative combination of electrolysis and Fe (II)-activated persulfate oxidation for improving the dewaterability of waste activated sludge. Bioresour. Technol. 2013, 136, 654–663. [Google Scholar] [CrossRef] [PubMed]
  17. Jin, B.; Wilén, B.M.; Lant, P. Impacts of morphological, physical and chemical properties of sludge flocs on dewaterability of activated sludge. Chem. Eng. J. 2004, 98, 115–126. [Google Scholar] [CrossRef]
  18. Novak, J.T.; Sadler, M.E.; Murthy, S.N. Mechanisms of floc destruction during anaerobic and aerobic digestion and the effect on conditioning and dewatering of biosolids. Water Res. 2003, 37, 3136–3144. [Google Scholar] [CrossRef] [PubMed]
  19. Wang, W.; Luo, Y.; Qiao, W. Possible solutions for sludge dewatering in China. Front. Environ. Sci. Eng. China 2010, 4, 102–107. [Google Scholar] [CrossRef]
  20. Liu, H.; Yang, J.; Zhu, N.; Zhang, H.; Li, Y.; He, S.; Yang, C.; Yao, H. A comprehensive insight into the combined effects of Fenton’s reagent and skeleton builders on sludge deep dewatering performance. J. Hazard. Mater. 2013, 258, 144–150. [Google Scholar] [CrossRef]
  21. Ke, M.Y. Probe into advanced sludge dewatering technology in Jimei Wastewater Treatment Plant. Water Wastewater 2011, 37, 40–43. [Google Scholar]
  22. Cao, B.; Zhang, W.; Wang, Q.; Huang, Y.; Meng, C.; Wang, D. Wastewater sludge dewaterability enhancement using hydroxyl aluminum conditioning: Role of aluminum speciation. Water Res. 2016, 105, 615–624. [Google Scholar] [CrossRef] [PubMed]
  23. Sorensen, P.B.; Christensen, J.R.; Bruus, J.H. Effect of small-scale solids migration in filter cakes during filtration of wastewater solids suspensions. Water Environ. Res. 1995, 67, 25–32. [Google Scholar] [CrossRef]
  24. Chen, Z.; Zhang, W.; Wang, D.; Ma, T.; Bai, R. Enhancement of activated sludge dewatering performance by combined composite enzymatic lysis and chemical re-flocculation with inorganic coagulants: Kinetics of enzymatic reaction and re-flocculation morphology. Water Res. 2015, 83, 367–376. [Google Scholar] [CrossRef] [PubMed]
  25. Novak, J.T.; O’Brien, J.H. Polymer conditioning of chemical sludges. J. Water Pollut. Control Fed. 1975, 47, 2397–2410. [Google Scholar]
  26. Bratby, J. Coagulation and Flocculation in Water and Wastewater Treatment; IWA Publishing: London, UK, 2016. [Google Scholar]
  27. Lee, C.H.; Liu, J.C. Sludge dewaterability and floc structure in dual polymer conditioning. Adv. Environ. Res. 2001, 5, 129–136. [Google Scholar] [CrossRef]
  28. Yang, R.; Li, H.; Huang, M.; Yang, H.; Li, A. A review on chitosan-based flocculants and their applications in water treatment. Water Res. 2016, 95, 59–89. [Google Scholar] [CrossRef] [PubMed]
  29. Zhang, W.; Shang, Y.; Yuan, B.; Jiang, Y.; Lu, Y.; Qin, Z.; Chen, A.; Qian, X.; Yang, H.; Cheng, R. The flocculating properties of chitosan-graft-polyacrylamide flocculants (II)—Test in pilot scale. J. Appl. Polym. Sci. 2010, 117, 2016–2024. [Google Scholar] [CrossRef]
  30. Hubbard, A.T. Encyclopedia of Surface and Colloid Science; CRC Press: Boca Raton, FL, USA, 2002; Volume 1. [Google Scholar]
  31. Overbeek, J.T.G. Colloid and Interface Science; Academic Press Inc.: Cambridge, MA, USA, 1977. [Google Scholar]
  32. Castro, M.J.; Kovensky, J.; Cirelli, A.F. Ecologically safe alkyl glucoside-based gemini surfactants. Arkivoc 2005, 12, 253–267. [Google Scholar]
  33. Hong, C.; Si, Y.; Xing, Y.; Wang, Z.; Qiao, Q.; Liu, M. Effect of surfactant on bound water content and extracellular polymers substances distribution in sludge. RSC Adv. 2015, 5, 23383–23390. [Google Scholar] [CrossRef]
  34. Fu, J.; Jiang, B.; Cai, W. Effect of synthetic cationic surfactants on dewaterability and settleability of activated sludge. Int. J. Environ. Pollut. 2009, 37, 113–131. [Google Scholar] [CrossRef]
  35. Seoul Water. Study on the Optimal Operation of a Rapid Coagulation and Sedimentation Process for the Reuse of Treated Wastewater. Available online: https://arisu.seoul.go.kr/sudo_eng/index.jsp (accessed on 9 April 2024).
  36. Mazaheri, R.; Ghazani, M.T.; Alighardashi, A. Effects of Moringa peregrina and ferric chloride (FeCl3) on water treatment sludge dewatering. Biosci. Biotechnol. Res. Asia 2018, 15, 975–980. [Google Scholar] [CrossRef]
  37. American Public Health Association. Standard Methods for the Examination of Water and Wastewater; American Public Health Association: Washington, DC, USA, 1926; Volume 6. [Google Scholar]
  38. Lin, Q.; Peng, H.; Zhong, S.; Xiang, J. Synthesis, characterization, and secondary sludge dewatering performance of a novel combined silicon–aluminum–iron–starch flocculant. J. Hazard. Mater. 2015, 285, 199–206. [Google Scholar] [CrossRef]
  39. Krahnstöver, T.; Zenker, A.; Baggenstos, M.; Kobler, B.; Leikam, K.; Koch, G.; Wintgens, T. Characterizing solids retention, head loss development and micropollutant removal in the case of direct powdered activated carbon dosage upstream of deep bed filtration. Environ. Sci. Water Res. Technol. 2019, 5, 2172–2181. [Google Scholar] [CrossRef]
  40. Li, Z.; Lu, P.; Zhang, D.; Chen, G.; Zeng, S.; He, Q. Population balance modeling of activated sludge flocculation: Investigating the influence of Extracellular Polymeric Substances (EPS) content and zeta potential on flocculation dynamics. Sep. Purif. Technol. 2016, 162, 91–100. [Google Scholar] [CrossRef]
  41. Echavarría, A.P.; Torras, C.; Pagan, J.; Ibarz, A. Fruit juice processing and membrane technology application. Food Eng. Rev. 2011, 3, 136–158. [Google Scholar] [CrossRef]
  42. Park, K.; Kim, P.; Kim, H.G.; Kim, J. Membrane fouling mechanisms in combined microfiltration-coagulation of algal rich water applying ceramic membranes. Membranes 2019, 9, 33. [Google Scholar] [CrossRef]
  43. Gupta, M.K. Handling and Disposal of Sludges from Combined Sewer Overflow Treatment: Phase 1, Characterization; Environmental Protection Agency, Office of Research and Development, Municipal Environmental Research Laboratory: Washington, DC, USA, 1977. [Google Scholar]
  44. Zheng, H.; Sun, Y.; Zhu, C.; Guo, J.; Zhao, C.; Liao, Y.; Guan, Q. UV-initiated polymerization of hydrophobically associating cationic flocculants: Synthesis, characterization, and dewatering properties. Chem. Eng. J. 2013, 234, 318–326. [Google Scholar] [CrossRef]
  45. Besra, L.; Sengupta, D.K.; Roy, S.K.; Ay, P. Influence of polymer adsorption and conformation on flocculation and dewatering of kaolin suspension. Sep. Purif. Technol. 2004, 37, 231–246. [Google Scholar] [CrossRef]
  46. Raynaud, M.; Vaxelaire, J.; Olivier, J.; Dieudé-Fauvel, E.; Baudez, J.C. Compression dewatering of municipal activated sludge: Effects of salt and pH. Water Res. 2012, 46, 4448–4456. [Google Scholar] [CrossRef]
  47. Verrelli, D.I.; Dixon, D.R.; Scales, P.J. Effect of coagulation conditions on the dewatering properties of sludges produced in drinking water treatment. Colloids Surf. A Physicochem. Eng. Asp. 2009, 348, 14–23. [Google Scholar] [CrossRef]
  48. Neyens, E.; Baeyens, J.; Dewil, R. Advanced sludge treatment affects extracellular polymeric substances to improve activated sludge dewatering. J. Hazard. Mater. 2004, 106, 83–92. [Google Scholar] [CrossRef] [PubMed]
  49. Chen, Y.; Yang, H.; Gu, G. Effect of acid and surfactant treatment on activated sludge dewatering and settling. Water Res. 2001, 35, 2615–2620. [Google Scholar] [CrossRef] [PubMed]
  50. Ye, C.; Wang, D.; Shi, B.; Yu, J.; Qu, J.; Edwards, M.; Tang, H. Alkalinity effect of coagulation with polyaluminum chlorides: Role of electrostatic patch. Colloids Surf. A Physicochem. Eng. Asp. 2007, 294, 163–173. [Google Scholar] [CrossRef]
  51. Hu, C.; Liu, H.; Qu, J.; Wang, D.; Ru, J. Coagulation behavior of aluminum salts in eutrophic water: Significance of Al13 species and pH control. Environ. Sci. Technol. 2006, 40, 325–331. [Google Scholar] [CrossRef] [PubMed]
  52. Lin, F.; Qin, W.; Wei, J.; Lv, J.; Yang, P. Effect of chemical regulation combined with mechanical filtration on deep dewatering and consolidation characteristics of sludge. Environ. Sci. Pollut. Res. 2023, 30, 89088–89100. [Google Scholar] [CrossRef] [PubMed]
Water 16 02303 g001
Figure 1. Flow chart of the experimental process used in the analysis of anaerobic sludge with coagulant and surfactant.
Figure 1. Flow chart of the experimental process used in the analysis of anaerobic sludge with coagulant and surfactant.
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Figure 2. Time to filtration test apparatus.
Figure 2. Time to filtration test apparatus.
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Figure 3. Filter press apparatus.
Figure 3. Filter press apparatus.
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Figure 4. Zeta potential of anaerobic sludge according to dosage of PAC.
Figure 4. Zeta potential of anaerobic sludge according to dosage of PAC.
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Figure 5. TTF profile of anaerobic sludge according to dosage of PAC.
Figure 5. TTF profile of anaerobic sludge according to dosage of PAC.
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Figure 6. Flux (a) and filtration rate (b) of anaerobic sludge according to dosage of PAC.
Figure 6. Flux (a) and filtration rate (b) of anaerobic sludge according to dosage of PAC.
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Figure 7. Zeta potential of anaerobic sludge according to dosage of POAE.
Figure 7. Zeta potential of anaerobic sludge according to dosage of POAE.
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Figure 8. TTF profile of anaerobic sludge according to dosage of POAE.
Figure 8. TTF profile of anaerobic sludge according to dosage of POAE.
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Figure 9. Flux (a) and filtration rate (b) of anaerobic sludge according to dosage of POAE.
Figure 9. Flux (a) and filtration rate (b) of anaerobic sludge according to dosage of POAE.
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Figure 10. Zeta potential of anaerobic sludge according to pH.
Figure 10. Zeta potential of anaerobic sludge according to pH.
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Figure 11. pH of anaerobic sludge according to coagulant (a) and surfactant (b) dosage.
Figure 11. pH of anaerobic sludge according to coagulant (a) and surfactant (b) dosage.
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Figure 12. Time to filtration of anaerobic sludge according to pH.
Figure 12. Time to filtration of anaerobic sludge according to pH.
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Figure 13. Filtrate and pressure profile of pressurized dewatering process for anaerobic sludge (POAE, 76 mg/L).
Figure 13. Filtrate and pressure profile of pressurized dewatering process for anaerobic sludge (POAE, 76 mg/L).
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Figure 14. Filtrate flux during pressurized dewatering process for anaerobic sludge (POAE, 76 mg/L).
Figure 14. Filtrate flux during pressurized dewatering process for anaerobic sludge (POAE, 76 mg/L).
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Figure 15. Filtrate and pressure profile of pressurized dewatering process for anaerobic sludge (POAE, 114 mg/L).
Figure 15. Filtrate and pressure profile of pressurized dewatering process for anaerobic sludge (POAE, 114 mg/L).
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Figure 16. Filtrate flux during pressurized dewatering process for anaerobic sludge (POAE, 151 mg/L).
Figure 16. Filtrate flux during pressurized dewatering process for anaerobic sludge (POAE, 151 mg/L).
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Table 1. Characteristics of anaerobic sludge.
Table 1. Characteristics of anaerobic sludge.
ParameterMoisture Content (%)TS 1
(%)		VS 2/TS 1
(%)		pHCOD (mg/L)TP
(mg/L)
Anaerobic sludge96.73.3047.278.1239,200130
Notes: 1 Total solid. 2 Volatile solid.
Table 2. Properties of PAC coagulant and POAE surfactant.
Table 2. Properties of PAC coagulant and POAE surfactant.
ParameterPACPOAE
Concentration (%)1748
Specific gravity1.191.0–1.2
pH3.5–5.54.0–6.0
Table 3. PAC coagulant dosage.
Table 3. PAC coagulant dosage.
CoagulantDosage (mg/L)
PAC1053155248761794
Table 4. POAE surfactant dosage.
Table 4. POAE surfactant dosage.
SurfactantDosage (mg/L)
POAE283876114151
Table 5. Physicochemical properties of dewatered cake and filtrate.
Table 5. Physicochemical properties of dewatered cake and filtrate.
DescriptionSludge (Raw)Sludge (POAE-76)Sludge (POAE-114)
Dewatered cake
Moisture contents (%)96.795.3072.7
Filtrate
COD (%)39,2001440440
TP (%)13032.30.5
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Song, E.; Kim, E.; Kim, G.W.; Jeong, C.J.; Lee, W.; Han, S.K. Dewaterability Enhancement of Anaerobic Sludge Using Polymeric Aluminum Chloride and Polyoxyethylene Alkyl Ether Surfactants. Water 2024, 16, 2303. https://doi.org/10.3390/w16162303

AMA Style

Song E, Kim E, Kim GW, Jeong CJ, Lee W, Han SK. Dewaterability Enhancement of Anaerobic Sludge Using Polymeric Aluminum Chloride and Polyoxyethylene Alkyl Ether Surfactants. Water. 2024; 16(16):2303. https://doi.org/10.3390/w16162303

Chicago/Turabian Style

Song, Eunhye, Eunju Kim, Gyeong Woo Kim, Cheol Jin Jeong, Wonbae Lee, and Seong Kuk Han. 2024. "Dewaterability Enhancement of Anaerobic Sludge Using Polymeric Aluminum Chloride and Polyoxyethylene Alkyl Ether Surfactants" Water 16, no. 16: 2303. https://doi.org/10.3390/w16162303

APA Style

Song, E., Kim, E., Kim, G. W., Jeong, C. J., Lee, W., & Han, S. K. (2024). Dewaterability Enhancement of Anaerobic Sludge Using Polymeric Aluminum Chloride and Polyoxyethylene Alkyl Ether Surfactants. Water, 16(16), 2303. https://doi.org/10.3390/w16162303

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