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Article

Old Landfill Leachate and Municipal Wastewater Co-Treatment by Sequencing Batch Reactor Combined with Coagulation–Flocculation Using Novel Flocculant

by
Radhakrishnan Naresh Kumar
1,
Somya Sadaf
1,
Mohini Verma
1,
Shubhrasekhar Chakraborty
1,2,
Shweta Kumari
1,
Veerababu Polisetti
3,*,
Parashuram Kallem
4,5,*,
Jawed Iqbal
1 and
Fawzi Banat
4
1
Department of Civil and Environmental Engineering, Birla Institute of Technology, Mesra, Ranchi 835215, Jharkhand, India
2
Department of Agriculture, Usha Martin University, Ranchi 835103, Jharkhand, India
3
Wallenberg Wood Science Center, Department of Fibre and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden
4
Center for Membranes and Advanced Water Technology (CMAT), Khalifa University, Abu Dhabi P.O. Box 127788, United Arab Emirates
5
Environmental Health and Safety Program, College of Health Sciences, Abu Dhabi University, Abu Dhabi P.O. Box 59911, United Arab Emirates
*
Authors to whom correspondence should be addressed.
Sustainability 2023, 15(10), 8205; https://doi.org/10.3390/su15108205
Submission received: 11 March 2023 / Revised: 28 April 2023 / Accepted: 15 May 2023 / Published: 18 May 2023
(This article belongs to the Special Issue Emerging Technologies in Wastewater Treatment and Resource Recovery: Recent Advances, Challenges and Future Trends)
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Abstract

:
The use of novel flocculants in combination with a sequencing batch reactor (SBR) for the treatment of landfill leachate and municipal wastewater has been shown to be an effective method for reducing polluted effluents. Co-treatment of landfill leachate with a mixture of municipal wastewater was performed at 5%, 10%, 15% and 20% in SBR and effluent was treated by coagulation–flocculation. SBR with 6 d hydraulic retention time (HRT) and 30 d solids retention time (SRT) removed 58 to 70% COD, 86 to 93% ammonia, 76 to 83% nitrate and 69 to 95% phosphate. Coagulation–flocculation with different dosages of alum and ferric chloride with polyacrylamide grafted gum ghatti (GGI-g-PAM) as a novel flocculant was used for chemical oxygen demand (COD), turbidity, total suspended solids (TSS) and color removal. Maximum COD removal was at 20% leachate, which was 74% with alum at 2800 mg/L and 77% with ferric chloride at 470 mg/L. Alum and ferric chloride with GGI-g-PAM flocculant removed 96% and 82% of turbidity and 80% and 82% TSS, respectively. At 20% leachate, combined treatment with SBR and coagulation–flocculation resulted in the total removal of 89% COD, 83% ammonia, 82% nitrate 98% turbidity and 93% TSS with alum. The combined treatment with ferric chloride resulted in a removal of 90% COD, 86% ammonia, 83% nitrate, 98% turbidity and 94% TSS. Except for nitrate combined treatment with both the coagulants at 20% landfill leachate to municipal wastewater ratio removed COD, ammonia, phosphate and TSS to a level that met international standards for discharges to inland surface water. As such, the use of new flocculants with SBR can help reduce water pollution from landfill leachate and municipal wastewater. In addition to coagulation–flocculation, other physico–chemical processes can also be studied as post-treatment options for the co-treatment of wastewater mixture.

1. Introduction

Municipal solid waste (MSW) management which includes various processes such as waste segregation, storage, collection, transfer, processing, and disposal in a sustainable manner faces many challenges in developing countries [1]. High-income group countries have economically and environmentally sound waste management practices due to the implementation of strict norms and regulations. However, developing countries are lagging in waste management owing to a large gap between policy and implementation.
In open dumps or landfills, MSW is exposed to all the environmental variables, particularly water, which solubilizes various organic and inorganic compounds resulting in leachate formation [2]. Leachate is a highly complex liquid that constitutes a combination of contaminants such as organic matter, inorganic ions, metals, and xenobiotic organic compounds [2,3]. Landfill leachate generates many pollutants that can damage soil, groundwater, and aquatic organisms. Furthermore, the composition of landfill leachates displays a large biological and physicochemical variability. This difference is due to key factors such as climate, type of waste, age of the landfill, moisture content, pH, and geographical location [4,5,6]. Leachate generation and environmental contamination are one of the main concerns in open waste dumps [7,8,9,10]. Landfill leachate is classified into three types according to landfill age, young (<5 years), medium (5–10 years), and old/stabilized (>10 years) [11]. The BOD/COD ratio of young leachate is 0.5–1.0, medium leachate is 0.1–0.5 and old leachate is <0.1 [11,12].
The pollution potential of landfill leachate and its toxicity necessitates treatment either on-site or by discharge to a wastewater treatment plant after some pre-treatment. Treatment of landfill leachate to meet the stringent discharge standards is challenging primarily because of spatial and temporal variations in quality and quantity [13,14]. Conventional activated sludge, SBR, and aerated lagoons based on suspended growth biomass techniques have also been researched for leachate treatment [15,16]. Anaerobic process for leachate treatment such as up-flow anaerobic sludge blanket reactor has been reported to be effective in reducing major types of organic matter present in leachate [17]. However, treatment of old leachate by biological process alone frequently fails to meet the stringent discharge standards due to the presence of recalcitrant organic compounds in the leachate. Therefore, treatment of old leachate in addition to biological treatment is commonly carried out in combination with physical and chemical processes such as coagulation–flocculation, adsorption, chemical oxidation or advanced oxidation processes, filtration, and ammonia stripping, etc. [18,19,20,21,22].
Biological treatment is typically used as a preliminary step for removing ammonia and readily biodegradable compounds in young landfill leachate. Several biological wastewater treatment methods such as trickling filters (TFs), activated sludge process (ASP), constructed wetlands (CWs), and moving bed biofilm reactors (MBBR) have been introduced over the decades to treat wastewater [23]. However, these methods have demonstrated significant performance against different pollutants, the requirement of the high area and energy are two important limitations in their operation. Additionally, biological methods are often ineffective in treating old leachate due to the low BOD5/COD ratio and high concentration of toxic substances [24,25]. Therefore, old landfill leachate biological systems are often coupled with processes such as air stripping, coagulation–flocculation, chemical oxidation, and adsorption either or post-treatment. Another strategy would be to co-treat landfill leachate with municipal wastewater to improve the low BOD:COD ratio and control leachate variability [26]. Co-treatment of landfill leachate with municipal wastewater could be a viable option mainly because of dilution which favors biodegradation. Thus, a competitive, cost-effective, and simple treatment process is desirable to deal with old landfill leachates [5,23].
Flocculation has been widely considered a simple and cost-effective method to treat landfill leachate. It is often used to remove suspended inorganic and organic, turbidity, total suspended salts, and dissolved nutrients (phosphate, nitrate, etc.). Owing to its operational flexibility and resistance to high biomass retention, sequencing batch reactor (SBR) has become a significant process to treat landfill leachates [14]. Our results in a previously published study showed that co-treatment of old landfill leachate and municipal wastewater in SBR was effective but required further treatment [24,27]. Hence, in this study, SBR effluent was treated by coagulation–flocculation using alum and ferric chloride with GGI-g- PAM as a novel flocculant. The primary goal was to explore the potential of using a combined SBR and coagulation–flocculation process to remove COD, ammonia, nitrate, phosphate, and TSS from landfill leachate and municipal wastewater.

2. Materials and Methods

2.1. Landfill Leachate and Municipal Wastewater Collection

Leachate from a landfill was collected from an open MSW dump site located at Jhiri village (23°24′ N and 85°15′ E) in Ranchi, Jharkhand, India. Open dumping at this site has been going on for the last 15 years and every day, the site receives ~700 tons of mixed waste. The dumped waste is not compacted at the landfill and there are no liner provisions. Leachate samples were collected in clean 20-L plastic containers from small ditches at the bottom of the waste heaps at the dump site. Samples were transported to the laboratory and stored at 4 °C until use. Municipal wastewater was collected from the equalization tank at the Birla Institute of Technology wastewater treatment plant, Mesra, Ranchi, India.

2.2. SBR + Coagulation–Flocculation for Co-Treatment of Landfill Leachate and Municipal Wastewater

The SBR was made of acrylic sheets measuring 14.8 cm (L) × 9.4 cm (W) × 30 cm (H) with 4.2 L total volume and 3 L working volume. The outlet of the SBR was located 4.5 cm from the base to prevent biomass loss. Activated sludge from an extended aeration wastewater treatment plant was used as inoculum for a start-up. During start-up, only municipal wastewater was fed into the SBR until a stable mixed liquor suspended solids (MLSS) concentration was attained. For rapid biomass growth and to maintain optimal working conditions in the SBR, the COD/N/P ratio was maintained at 100:6:2 with glucose and sodium acetate, ammonium chloride and potassium dihydrogen phosphate. Co-treatment was initiated by adding 2% (v/v) landfill leachate with municipal wastewater as part of the daily dosage. SBR was fed with increasing doses of leachate to municipal wastewater at 5%, 10%, 15%, and 20% (v/v) for co-treatment.
The SBR for co-treatment was operated on a 24-h cycle with 6 days of HRT and 30 days of SRT. Each daily cycle was divided into the following phases: 5 min of filling, 17 h of aerobic reaction (aeration and agitation), 6 h of anoxic reaction (agitation only), 50 min of settling, and 5 min of decanting. At the beginning of the filling phase, 500 mL of the combined influent was fed to SBR. Even after mixing leachate with wastewater BOD:COD ratio remained below the ideal value for biological treatment. Therefore, glucose was added at the beginning of the aerobic phase to achieve a BOD:COD ratio >0.5. The SBR was operated in a post-anoxic mode for denitrification, sodium acetate was added at the beginning of the anoxic phase to serve as a C source. For the aerobic phase, the aquarium pump supplied air and mixing was performed with a magnetic stirrer. For the anoxic phase, the air supply was stopped while agitation was maintained. The SBR was kept at room temperature (20–25 °C). Samples were taken from the SBR at the beginning and end of the aerobic phase, at the beginning of the anoxic phase, and at the end of each daily cycle to analyze COD, ammonia, nitrate, phosphate and MLSS analysis.
Post-treatment of the SBR effluent was performed by coagulation and flocculation. Coagulation–flocculation was performed in the single batch run on standard jar test apparatus using alum and ferric chloride as coagulants together with the new flocculant GGI-g-PAM. The flocculant used, GGI-g-PAM, was provided by researchers at the Department of Chemistry, BIT, Mesra and synthesized using a microwave-assisted method. The initial pH of the samples was adjusted to pH 6 for alum and pH 5 for ferric chloride using 1 N H2SO4 [28]. Coagulation–flocculation was initiated by mixing wastewater at 200 rpm for 3 min followed by slow mixing at 60 rpm for 20 min and finally, sedimentation for 1 h. Treatment efficiency of coagulation–flocculation was assessed from COD, TSS, turbidity, and color. For this purpose, samples were collected from reaction vessels at regular intervals and analyzed for various physico–chemical parameters as per the standard procedures for landfill leachate analysis.

2.3. Analysis

Landfill leachate and municipal wastewater properties such as pH, electrical conductivity (EC), TSS, total dissolved solids (TDS), MLSS, turbidity, color, COD, BOD5, NH3-N, NO3-N and PO43− were determined according to the procedures detailed in the standard methods [29]. The sludge volume index was determined after 30 min of settling time by measuring sludge volume and MLSS. More information about the characterization techniques can be found in Supplementary File.

2.4. Data Analysis

Data were analyzed using MS Excel and Sigma Plot (Ver. 13) to prepare tables and figures. Statistically, the significant difference in the mean concentration of COD, turbidity, TSS, and color removal by both alum and ferric chloride at different landfill leachate-wastewater concentrations was evaluated by using univariate analysis of variance (ANOVA). If a significant difference was found, ANOVA followed by Tukey post hoc analysis was applied to compare the mean concentration of the subcategories. A correlation analysis was performed to determine the relationship between coagulant dose and effluent characteristics when significant landfill leachate-effluent concentration was detected using Tukey post hoc analysis.

3. Results and Discussion

3.1. Physico-Chemical Characteristics of Landfill Leachate and Municipal Wastewater

Leachate physico-chemical characteristics are mainly dependent on waste age, waste composition, moisture and oxygen availability, site hydrology and operational conditions of the landfill. Dumpsite in Ranchi produces leachate most times of the year and leachate production ceases during summer. The higher atmospheric temperature in the dry season leads to conditions that prevent leachate generation. COD, anions, and cations concentration in leachate was maximum during winter months (December to February) and the concentration of most solutes was low during the monsoon period (June to August) which was mainly due to dilution effects induced by precipitation. Dumpsite in Ranchi, being 15 years old, is in the methane-producing phase [11].
The leachate from the landfill contained high COD (4300 ± 1200 mg/L) and low BOD (70 ± 40 mg/L) which resulted in a low BOD5/COD ratio. pH of 7.6, high ammonia (300 ± 80 mg/L), low nitrate (25 ± 7 mg/L) and phosphate (50 ± 25 mg/L) indicated that the landfill was in the methanogenic phase. Other leachate characteristics were EC 8.9 ± 1.9 mS/cm, TDS 6700 ± 3500 mg/L, and TSS 4400 ± 2500 mg/L. The color of the leachate was dark brown (λmax 436 nm). Characterization of the municipal wastewater showed BOD5 (250 ± 100 mg/L), COD (450 ± 120 mg/L), ammonia (40 ± 2 mg/L) and phosphate (10 ± 3 mg/L). Other municipal wastewater characteristics were EC 0.7 ± 0.2 mS/cm, TDS 450 ± 50 mg/L, and TSS 360 ± 30 mg/L. The municipal wastewater had slightly low BOD due to this even after mixing landfill leachate with wastewater BOD/COD ratio was <0.5, which necessitated external carbon addition to maintain BOD/COD ratio >0.5. Such problems with a low BOD /COD may not occur when co-treatment is applied at the field scale if municipal wastewater has a high BOD and the volume of landfill leachate is also low [30].
BOD/COD ratio was 0.02 in the present study. This ratio is a good indicator of leachate biodegradability which declines with time. A low BOD/COD ratio shows a low concentration of volatile fatty acids and a higher concentration of humic and fulvic acid-like compounds in leachate [31]. A low BOD/COD ratio has also been reported for leachate from a landfill in Kuala Lumpur, Malaysia [32]. The reason for low BOD and high COD is due to the decomposition of labile substances in leachate and the persistence of recalcitrant compounds in leachate. It is well established that wastes in dumpsites decompose in four phases i.e., aerobic, anaerobic, initial methanogenic and stable methanogenic phase [3]. These four phases can be designated as the aerobic phase where leachate occurs at near neutral pH, the anaerobic phase in which leachate has high BOD and COD concentrations and acidic pH followed by the initial methanogenic phase in which BOD and COD concentrations in leachate decrease and pH increases and final stable methanogenic phase in which BOD:COD ratio decreases to <0.1 [3]. Hence, old leachate contains significantly greater concentrations of refractory organic matter (fulvic-like and humic-like substances) as compared to young leachate which is difficult to be completely removed by bacterial-based processes [2,6,33].
Among the nitrogenous compounds, ammonia nitrogen (NH3-N) is often the major pollutant detected in old landfill leachate. Ammonia concentration decreased during monsoon season which might be due to dilution effects. Hydrolysis and fermentation of nitrogenous fractions of biodegradable matter are responsible for high ammonia concentration in old landfill leachate [34]. In the long term, ammonia is the most significant pollutant in leachate as there is no mechanism for its transformations under methanogenic conditions [3]. As the landfill age increases, the landfill enters anoxic/anaerobic phases where the nitrogen cycle is inhibited mainly due to decreased nitrification rate which results in ammonia accumulation [3]. Present findings on ammonia agree with the reported literature which shows that the concentrations vary from tens or hundreds of mg/L to 2000–3000 mg/L in different landfills [7,35,36]. Kulikowska and Klimiuk [37] reported increased ammonia concentration from 98 to 364 mg/L after 6 y of landfill operations. El-Salam and Bu-Zuid (2015) found a similar range of ammonia concentration in leachate from a landfill in Egypt (190 to 410 mg/L). Halie and Abiye [38] reported moderate ammonia concentration (120 mg/L) in leachate from 10 y old landfill in Addis Ababa, Ethiopia. El-Salam and Abu-Zuid [36] reported nitrate at 1.4 mg/L which is very low compared to the present study. High nitrate concentration in leachate could be attributed to the presence of household and agricultural wastes in a landfill. Phosphate is released in leachate mainly due to the degradation of organic matter that contain phospholipids and phosphoproteins and from the dumping of pesticide residues and phosphate fertilizers in landfill [39,40]. Fatta et al. [39] reported phosphate concentration from an old landfill in Greece which varied from 9.7 to 16.8 mg/L. When compared to the values of the present study, low phosphate concentration (2.25 mg/L) has been reported from the MSW dumpsite in Varanasi, India [41].

3.2. SBR for Co-Treatment of Landfill Leachate and Municipal Wastewater

COD removal in SBR was 30.6–46.6% and its removal efficiency declined as leachate concentration increased >15% (Table 1 and Figure 1). A drop in COD removal is expected when the volume of leachate increases in the daily loading, as the non-biodegradable organic matter would have also increased in the system [24]. Earlier studies on landfill leachate treatment have reported COD removal efficiency of 90–94% [42,43]. The moderate COD removal in the present study as compared to other studies may be due to the high concentrations of refractory substances normally present in stabilized landfill leachate [44].
To achieve higher ammonia, nitrate, and phosphate removal, the SBR was operated with a long SRT, and the slightly lower COD removal could be due to the high SRT in addition to the non-biodegradable organics [45,46]. Ammonia removal varied between 85.6–93.1%, with a maximum reduction of 10% leachate (Figure 1). The ammonia removal was mainly due to nitrification as evident from the concurrent increase in nitrate concentration (Equations (1) and (2)). In addition, pH 7–8 was maintained in the SBR which did not result in ammonia removal by volatilization [25,47]. The SBR was operated at post-anoxic mode and denitrification resulted in nitrate removal of 75.6–83.3%. Nitrate reduction efficiency was not affected by increasing the leachate concentration in SBR. Kundu et al. [48] reported similar nitrate reduction efficiency when treating slaughterhouse wastewater in SBR. Phosphate removal efficiency varied from 75.9 to 99.8% and the highest removal was achieved when the system was fed with 10% of the landfill leachate. Most of the phosphate was removed at the end of the aerobic phase [48].
NH4+ + 1.5O2 → NO2− + 2H+ + H2O
NO2− + 0.5O2 → NO3−

3.3. Coagulation–Flocculation

COD, turbidity, TSS and color removal efficiency following coagulation–flocculation as a post-treatment option to SBR increased as the concentration of landfill leachate increased in the wastewater mixture (Figure 2 and Figure 3). In general, leachate treatment efficiency either remained stable or dropped as both coagulant doses increased. Univariate ANOVA revealed a statically significant difference between alum and ferric chloride for COD removal (alum: F3.0 = 28.8, p ≤ 0.001 (Figure 2a); FeCl3: F3.0 = 4.67, p ≤ 0.01 (Figure 3a)), turbidity (alum: F3.0 = 367.9, p ≤ 0.001 (Figure 2b); FeCl3: F3.0 = 18.2, p ≤ 0.001 (Figure 3b)), TSS (alum: F3.0 =13.3, p ≤ 0.001 (Figure 2c); FeCl3: F3.0 = 4.52, p ≤ 0.001 (Figure 3c)) and color (alum: F3.0 = 39.5, p ≤ 0.001 (Figure 2d); FeCl3: F3.0 = 8.34, p ≤ 0.001 (Figure 3d)) between 5%, 10%, 15% and 20% leachates. The post hoc t-test indicated that COD, turbidity and TSS removal by alum led to insignificant differences (p > 0.05) at 5% and 10% leachate concentrations, whereas the data showed significant differences (p < 0.05) at 15% and 20% landfill leachate. Color removal by alum showed an insignificant difference (p > 0.05) at 5% leachate while at 10%, 15% and 20% leachate significant difference (p < 0.05) was observed. The main reason for this could be due to the higher mixing ratio of leachate at (10%, 15% and 20%) compared to the 5% treatment, it could be that as the leachate increases the color strength would increase too leading to its better removal. The post hoc t-test showed that COD, turbidity, TSS and color removal by ferric chloride had insignificant differences at 5%, 10%, and 15% leachate while there was a significant difference at 20% leachate.
COD removal was higher with ferric chloride than alum at all tested doses. Aziz et al. (2007) reported that ferric chloride gave the best results in removing color, COD, turbidity and TSS among the different coagulants tested such as alum, ferric chloride, ferrous sulfate, and ferric sulfate [49]. The optimum dose of alum was 2800 mg/L, while for ferric chloride the optimum dose was 470 mg/L, with GGI-g-PAM as flocculant. At 20% leachate with an optimal dose of alum and ferric chloride, the respective COD concentrations of 195 and 172 mg/L remained in the effluent. Moreover, at the same dose and leachate concentration, alum removed 96% of turbidity and 80% of TSS, while ferric chloride removed 82% of turbidity and 81% of TSS. Color removal at all leachate concentrations showed a similar trend for both coagulants. The correlation coefficient (R2) between the different dosages of alum and FeCl3 for COD, turbidity, TSS and color removal at 20% leachate showed a negative correlation (Table 2). A high negative correlation indicates an inverse relationship between dosage and solids removal as dosages higher than the optimal dose affect coagulation efficiency [50,51,52]. This is mainly because charge reversal and destabilizing of colloidal particles occur as the dosage increases thereby lowering the treatment efficiency. The overall treatment efficiencies of SBR + coagulation–flocculation in different ratios are shown in Table 3. Co-treatment in SBR improved the treatability of landfill leachate. The process efficiently removed ammonia and nitrate while coagulation–flocculation mainly removed TSS and color from the waste mixture. Except for nitrate, the final effluent with both coagulants at 20% leachate was able to meet Indian standards for the discharge of treated wastewater to inland water.
Coagulation–flocculation is a highly pH-dependent process, as the nature of polymeric metal species that are produced from the dissolution of metal coagulants in water is greatly influenced by system pH. Coagulation–flocculation involves a balance of two competitive forces which first one is between H+ and metal hydrolysis products with colloids and organic ligands at low pH and another is between hydroxide ions and anions with metal hydrolysis products at higher pH [53]. Therefore, poor removal efficiency often occurs at low pH due to the inability of generated metal species to participate in coagulation reactions. Present results on coagulation–flocculation agree with those reported by Li et al. [54] and Maranon et al. [55]. Li et al. [54] and Maranon et al. [55] in their studies found that COD removal was better for ferric chloride in acidic pH and for alum at pH 6 from stabilized leachate. Ferric ions in acidic conditions hydrolyze to form polynuclear cations such as Fe(OH)2+, Fe2(OH)24+, Fe3(OH)45+ and other species with positive charges which interacts with negatively charged colloids leading to charge neutralization and hence destabilization of colloidal particles. On the other hand, in the case of alum, the maximum amount of coagulant was hydrolyzed to Al3+, Al(OH)2+ and Al(OH)4- ions at pH 6 which are in equilibrium with amorphous Al(OH)3(am) solid phase that precipitates to form floc particles onto the surface of which colloidal particles becomes adsorbed [56]. Novel flocculant GGI-g-PAM led to better treatment efficiency mainly by bridging mechanism. In the bridging mechanism, colloidal particles become adsorbed into long-chain polymers in such a manner that an individual chain can become attached to two or more particles causing bridging them together.

4. Conclusions

The landfill leachate used was stable, but the municipal wastewater used was moderate in strength. Co-treatment of 5%, 10%, 15% and 20% of landfill leachate with wastewater was performed by a combination of SBR and coagulation–flocculation. The efficiency of SBR treatment decreased with increasing in leachate concentration as evidenced by COD and nutrient removal. The SBR effluent was treated with different doses of alum at pH 6 and ferric chloride at pH 5 with 100 mg/L GGI-g-PAM. At a leachate concentration of 20%, the combined treatment with alum resulted in a total removal of 89% COD, 83% ammonia, 82% nitrate, 98% turbidity and 93% TSS. The combined process with ferric chloride resulted in 90% COD, 86% ammonia, 83% nitrate, 98% turbidity and 94% TSS removal. Overall, this study has revealed that the combination of SBR with coagulation/flocculation using novel flocculants is an effective and efficient method for both landfill leachate and municipal wastewater treatment. This method is simple, eco-friendly, and easy to implement. Nonetheless, other physicochemical processes may also be explored to optimize the best treatment scheme.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/su15108205/s1.

Author Contributions

R.N.K.: conceptualization, methodology, data curation, writing—original draft preparation, supervision, writing—reviewing and editing. S.S.: writing—original draft preparation. M.V.: sampling and analysis. S.C.: data curation, software. S.K.: data curation, software. J.I.: writing—reviewing and editing. V.P.: writing—reviewing and editing P.K. and F.B.: writing—reviewing and editing. All authors have read and agreed to the published version of the manuscript.

Funding

Mohini Verma thanks the Birla Institute of Technology, Mesra, Ranchi, India for providing Institute fellowship to carry out doctoral research work. Authors (Parashuram Kallem and Fawzi Banat) would like to thank the Center for Membranes and Advanced Water Technology (CMAT) at Khalifa University of Science and Technology, the United Arab Emirates for financial support through Grant No. RC2-2018-009. V.P. is grateful for the postdoctoral opportunities provided by the Knut and Alice Wallenberg Foundations. V.P. wished to thank KTH Royal Institute of Technology for the financial support to publish this article with open access.

Data Availability Statement

Data is contained within the article.

Acknowledgments

Thanks to Gautam Sen, Department of Chemistry, BIT Mesra for providing GGI-g-PAM.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Removal efficiency of COD and nutrients at different concentrations in SBR.
Figure 1. Removal efficiency of COD and nutrients at different concentrations in SBR.
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Figure 2. Variations in (a) COD, (b) turbidity, (c) TSS and (d) color removal efficiency at different concentrations of alum with GGI-g-PAM flocculant at various landfill leachate-wastewater concentrations.
Figure 2. Variations in (a) COD, (b) turbidity, (c) TSS and (d) color removal efficiency at different concentrations of alum with GGI-g-PAM flocculant at various landfill leachate-wastewater concentrations.
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Figure 3. Variations in (a) COD, (b) turbidity, (c) TSS and (d) color removal efficiency at different concentrations of ferric chloride with GGI-g-PAM flocculant at various landfill leachate-wastewater concentrations.
Figure 3. Variations in (a) COD, (b) turbidity, (c) TSS and (d) color removal efficiency at different concentrations of ferric chloride with GGI-g-PAM flocculant at various landfill leachate-wastewater concentrations.
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Table
Table 1. Removal efficiency of COD and nutrients (n = 3, ±S.D.) following co-treatment of landfill leachate with municipal wastewater at different concentrations in SBR.
Table 1. Removal efficiency of COD and nutrients (n = 3, ±S.D.) following co-treatment of landfill leachate with municipal wastewater at different concentrations in SBR.
Aerobic PhaseAnoxic Phase
COD (mg/L)Ammonia (mg/L)Phosphate (mg/L)COD (mg/L)Nitrate (mg/L)Phosphate
(mg/L)
IE1% RIE1% RIE1% RE2% RIE2% RE2% R
5%1404 ± 69750 ± 3146.6 ± 4172 ± 2419 ± 1.589 ± 12.9 ± 0.10.9 ± 0.165 ± 1.6420 ± 3861 ± 2.8156 ± 2637 ± 576 ± 10.4 ± 0.256 ± 17
10%1502 ± 73884 ± 9341.1 ± 3189 ± 2213 ± 593 ± 34.1 ± 0.80.9 ± 0.478 ± 5450 ± 2063 ± 1.3160 ± 939 ± 876 ± 3.40.2 ± 0.178 ± 22
15%1500 ± 401043 ± 6730.5 ± 6160 ± 1618.2 ± 1289 ± 62.2 ± 0.70.3 ± 0.286 ± 5525 ± 3961 ± 2.8145 ± 325 ± 583 ± 30.2 ± 0.133 ± 12
20%1770 ± 801100 ± 10137.8 ± 5169 ± 1427.1 ± 584 ± 42.0 ± 0.61.0 ± 0.250 ± 2750 ± 4447 ± 4164 ± 929 ± 882 ± 50.6 ± 0.240 ± 18
I represent influent in SBR, E1 and E2 is the respective effluent of aerobic and anoxic phase in SBR. % R indicates removal in percentage. A indicates ammonia, N nitrate and P phosphate.
Table
Table 2. Correlation coefficient between coagulant dose and effluent characteristics at 20% leachate concentration with municipal wastewater.
Table 2. Correlation coefficient between coagulant dose and effluent characteristics at 20% leachate concentration with municipal wastewater.
Alum DoseCODTurbidityTSSColor
Alum dose1
COD−0.80 *1
Turbidity−0.99 *0.78 *1
TSS−0.67 *0.86 *0.71 *1
Color−0.380.37 *0.480.71 *1
FeCl3 doseCODTurbidityTSSColor
FeCl3 dose1
COD−0.70 *1
Turbidity−0.97 *0.76 *1
TSS−0.94 *0.73 *0.99 *1
Color−0.92 *0.83 *0.98 *0.96 *1
* Denotes significant correlation.
Table
Table 3. Final effluent characteristics after combined SBR + coagulation–flocculation.
Table 3. Final effluent characteristics after combined SBR + coagulation–flocculation.
SBR + Coagulation–
Flocculation
(Alum)		COD
(mg/L)		Ammonia
(mg/L)		Nitrate
(mg/L)		Phosphate
(mg/L)		TSS
(mg/L)
5% (Leachate)31922340.7138
10% (Leachate)30615370.01158
15% (Leachate) 26320200.2150
20% (Leachate)19527250.6100
SBR + Coagulation–
Flocculation
(Ferric chloride)
5% (Leachate)18517320.7175
10% (Leachate) 15011350.01138
15% (Leachate)16515220.3111
20% (Leachate)17222240.590
* Wastewater
discharge criteria		25050105200
* Treated wastewater discharge criteria in India (Source: Central Pollution Control Board, India).
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Kumar, R.N.; Sadaf, S.; Verma, M.; Chakraborty, S.; Kumari, S.; Polisetti, V.; Kallem, P.; Iqbal, J.; Banat, F. Old Landfill Leachate and Municipal Wastewater Co-Treatment by Sequencing Batch Reactor Combined with Coagulation–Flocculation Using Novel Flocculant. Sustainability 2023, 15, 8205. https://doi.org/10.3390/su15108205

AMA Style

Kumar RN, Sadaf S, Verma M, Chakraborty S, Kumari S, Polisetti V, Kallem P, Iqbal J, Banat F. Old Landfill Leachate and Municipal Wastewater Co-Treatment by Sequencing Batch Reactor Combined with Coagulation–Flocculation Using Novel Flocculant. Sustainability. 2023; 15(10):8205. https://doi.org/10.3390/su15108205

Chicago/Turabian Style

Kumar, Radhakrishnan Naresh, Somya Sadaf, Mohini Verma, Shubhrasekhar Chakraborty, Shweta Kumari, Veerababu Polisetti, Parashuram Kallem, Jawed Iqbal, and Fawzi Banat. 2023. "Old Landfill Leachate and Municipal Wastewater Co-Treatment by Sequencing Batch Reactor Combined with Coagulation–Flocculation Using Novel Flocculant" Sustainability 15, no. 10: 8205. https://doi.org/10.3390/su15108205

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