Secondary effluent purification towards reclaimed water production through the hybrid post-coagulation and membrane distillation technology: A preliminary test
Graphical abstract
Introduction
Municipal wastewater is mainly treated by activated sludge (AS) process including adsorption-biodegration (AB) process, sequencing batch reactor (SBR) activated sludge process and anaerobic-anoxic-oxic (A2/O) process (Daverey et al., 2019; Huang et al., 2019). Vast majority of the treated municipal wastewater is directly discharged into the receiving water bodies, which is actually a waste of valuable freshwater resource (Qiao et al., 2018; Gu et al., 2019). The secondary effluent of the conventional biological process is used as a significant source of the high-grade reclaimed water in Singapore, which is named NEWater (PUB, 2019). The treated-used water is further purified by the advanced membrane technology and ultra-violet disinfection to produce NEWater. The reclamation of secondary effluent from municipal wastewater treatment plants has received much more attention owing to its large reserve and relatively easy to reach the standard (Jin et al., 2013; Si et al., 2019).
The reclaimed water can serve as an alternative source of water for multifarious applications, such as agriculture, urban, environmental and industrial uses (Gikas and Tchobanoglous, 2009; Zalacain et al., 2019). Moreover, reclaimed water is a stable and comparatively untapped source of water, less affected by climatic and seasonal changes (Racar et al., 2019). Previous studies reported the production of reclaimed water from municipal wastewater through pressure-driven microfiltration (MF), ultrafiltration (UF) and reverse osmosis (RO) (Ghayeni et al., 1996; Ravazzini et al., 2005; Gu et al., 2019). Whilst, high energy consumption and serious membrane fouling restricted the application of pressure-driven membrane filtration technology.
Different to the pressure-driven membrane separation processes (MF, UF, RO, etc.), membrane distillation (MD) is a thermal-driven membrane separation method (Khumalo et al., 2019). Membrane fouling in MD procedure is less problematic because MD utilizes a microporous hydrophobic membrane whose pores are relatively large and not easy to be clogged (Lawson and Lloyd, 1997). Moreover, MD procedure requires low operating temperature, and the unit could be combined with alternative energy sources, such as industrial waste heat, solar and geothermal energy (Hejazi et al., 2019). Recently, application of MD technology for water purification has received increasing attention in water and wastewater treatment (Li et al., 2016).
The secondary effluent from municipal wastewater treatment plant contains a large amount of dissolved and refractory organic matter, inorganic substances and pathogens (Gao et al., 2019; Ibn Abdul Hamid et al., 2019). Pretreatment of the secondary effluent before MD filtration procedure is quite necessary. Coagulation, which can remove colloidal particles, suspended solids (SS) and natural organic matter (NOM), is one of the most commonly-used and economical wastewater treatment process (Zhu et al., 2016; Zhao et al., 2017). Previous studies reported wide application of primary coagulation with conventional Al-based coagulants before MF (Jin et al., 2015), nanofiltration (NF) (Yu et al., 2016) and UF-RO processes (Shang et al., 2019), with the results demonstrated the enhanced removal of foulants and reduced membrane fouling. Similar conclusions could be achieved during coagulation-MD hybrid process as previously reported (Wang et al., 2008; Li et al., 2016; Choudhury et al., 2019). Different from the biologically treated coking wastewater and recirculating cooling water as they reported, secondary effluent from municipal wastewater treatment plants has larger reserve and is relatively easier to reach the reuse standard. Since MD is a recently developed membrane filtration technology, few studies reported the performance of the hybrid coagulation and membrane distillation (C-MD) procedure for further purification of secondary effluent, especially using the emerging titanium coagulants for coagulation.
Compared with the conventional Al- and Fe-based coagulants, the emerging Ti-based coagulants are becoming increasingly attractive due to i) its strong coagulation capability at least comparable to that of Al- and Fe-based coagulants (Wu et al., 2011; Zhao et al., 2013, 2015), and ii) the titanium-coagulated sludge recycling to produce functional nano-TiO2 particles (Huang et al., 2015; Chi et al., 2019). This study investigated both coagulation performance of polytitanium chloride (PTC) for the treatment of secondary effluent (PAC coagulation as reference), and the subsequent MD filtration performance in terms of both permeation flux and membrane fouling. Influence of operation conditions (with/without coagulation, temperature and flow arte, etc.) on the performance of the hybrid C-MD process were included. Mechanisms of the PTC-coagulation and the membrane fouling during MD filtration were also studied.
Section snippets
Raw water and coagulants
Raw water was the secondary effluent of the A2/O process from the secondary sedimentation tank of Everbright Water Limited in Jinan, Shandong Province, China. General properties of the test water included: residual turbidity = 1.07 ± 0.14 NTU, zeta potential = −9.28 ± 3.48 mV, ultra-violet absorbance at 254 nm (UV254) = 0.097 ± 0.009 cm−1, pH = 7.91 ± 0.53 and dissolved organic carbon (DOC) = 16.42 ± 0.07 mg/L.
Two typical coagulants, polyaluminum chloride (PAC) and polytitanium chloride (PTC),
Performance of post-coagulation
Performance of post-coagulation was investigated in terms of both post-coagulation efficiency and post-coagulation mechanism. The emerging PTC coagulant was expected to produce the effluent with higher quality than conventional PAC coagulant. High-quality effluent indicated the superior performance of the subsequent DCMD procedure in terms of both enhanced permeation flux and reduced membrane fouling. Investigation of coagulation mechanisms would be helpful for the follow-on analysis of the
Conclusions
This study proved that coagulation-MD hybrid treatment process was feasible to purify secondary effluent towards reclaimed water production. Two coagulants, PAC and PTC, were utilized for secondary effluent pretreatment, followed by DCMD to further purify coagulated effluent for improving effluent quality and mitigate membrane fouling. The PTC coagulated effluent achieved lower residual turbidity and higher UV254 and DOC removal efficiencies, and the flocs formed by PTC had bigger size and
CRediT authorship contribution statement
Xiao Liu: Methodology, Software, Validation, Investigation, Formal analysis, Data curation, Writing - original draft. Chang Tian: Software, Resources, Supervision. Wenhao Sun: Investigation. Yanxia Zhao: Conceptualization, Methodology, Resources, Writing - review & editing, Project administration, Funding acquisition. Kaimin Shih: Supervision, Writing - review & editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work was supported by the grants from the National Natural Science Foundation of China (No. 51978311) and Natural Science Foundation of Shandong Province, China (No. ZR2019BEE044).
References (63)
- et al.
Principles and applications of direct contact membrane distillation (DCMD): a comprehensive review
Desalination
(2016) - et al.
Formation of chlorination by-products in waters with low SUVA--correlations with SUVA and differential UV spectroscopy
Water Res.
(2007) - et al.
Experimental study of desalination using direct contact membrane distillation: a new approach to flux enhancement
J. Membr. Sci.
(2004) - et al.
Effect of turbidity on micropollutant removal and membrane fouling by MIEX/ultrafiltration hybrid process
Chemosphere
(2019) - et al.
Fouling and wetting in the membrane distillation driven wastewater reclamation process - a review
Adv. Colloid Interface Sci.
(2019) - et al.
Optimized coagulation pretreatment alleviates ultrafiltration membrane fouling: the role of floc properties and slow-mixing speed on mechanisms of chitosan-assisted coagulation
J. Environ. Sci.
(2019) - et al.
Sustainable use of water in the aegean islands
J. Environ. Manag.
(2009) - et al.
Purifying surface water contaminated with industrial failure using direct contact membrane distillation
Separ. Purif. Technol.
(2020) - et al.
An innovative anaerobic MBR-reverse osmosis-ion exchange process for energy-efficient reclamation of municipal wastewater to NEWater-like product water
J. Clean. Prod.
(2019) - et al.
Effect of intermittent operation on performance of a solar-powered membrane distillation system
Separ. Purif. Technol.
(2019)
Customizing anaerobic digestion-coupled processes for energy-positive and sustainable treatment of municipal wastewater
Renew. Sustain. Energy Rev.
Effect of using polydimethyldiallylammonium chloride as coagulation aid on polytitanium salt coagulation performance, floc properties and sludge reuse
Separ. Purif. Technol.
Effects of epichlorohydrin - dimethylamine on polytitanium chloride coagulation and membrane fouling in humic-kaolin water treatment: dosage, dose method and solution pH
Separ. Purif. Technol.
Effects of polytitanium chloride and polyaluminum chloride pre-treatment on ultrafiltration process: floc properties and membrane fouling
J. Taiwan Inst. Chem. Eng.
Coagulation of dissolved organic matter in surface water by novel titanium (III) chloride: mechanistic surface chemical and spectroscopic characterisation
Separ. Purif. Technol.
Comparison of the effects of ozone, biological activated carbon (BAC) filtration and combined ozone-BAC pre-treatments on the microfiltration of secondary effluent
Separ. Purif. Technol.
Flow rate influence on direct contact membrane distillation experiments: different empirical correlations for Nusselt number
J. Membr. Sci.
An analysis of the chemical safety of secondary effluent for reuse purposes and the requirement for advanced treatment
Chemosphere
Application of hybrid coagulation microfiltration with air backflushing to direct sewage concentration for organic matter recovery
J. Hazard Mater.
Congo red dye removal by direct membrane distillation using PVDF/PTFE membrane
Separ. Purif. Technol.
Probing reactivity of dissolved organic matter for disinfection by-product formation using XAD-8 resin adsorption and ultrafiltration fractionation
Water Res.
Membrane distillation
J. Membr. Sci.
Advanced treatment of biologically treated coking wastewater by membrane distillation coupled with pre-coagulation
Desalination
Surface hydrophobicity based heat and mass transfer mechanism in membrane distillation
J. Membr. Sci.
Study of advancement to higher temperature membrane distillation
Desalination
Assessment of trihalomethane (THM) precursors using specific ultraviolet absorbance (SUVA) and molecular size distribution (MSD)
J. Water Process Eng.
Recovery of sludge produced from Ti-salt flocculation as pretreatment to seawater reverse osmosis
Desalination
Experimentally-validated computational simulation of direct contact membrane distillation performance
Int. J. Heat Mass Tran.
NO removal of mortar mixed with titania produced from Ti-salt flocculated sludge
J. Ind. Eng. Chem.
Heat transport and membrane distillation coeffificients in direct contact membrane distillation
J. Membr. Sci.
Impact of secondary effluent from wastewater treatment plants on urban rivers: polycyclic aromatic hydrocarbons and derivatives
Chemosphere
Cited by (19)
Management of secondary effluent using novel membrane technology to recover water and magnesium ions for phosphate precipitation: An integrated pilot-scale study
2024, Separation and Purification TechnologyPolytitanium sulfate rich with dominant-flocculated-species prepared by electrodialysis towards ceramic membrane fouling control
2024, Separation and Purification TechnologyHydrophobic Zn-doped Fe<inf>2</inf>O<inf>3</inf>/PVDF-Co-HFP composite membranes for enhanced water recovery using direct contact membrane distillation
2024, Journal of Industrial and Engineering ChemistryDopamine-functionalized PTFE membranes with enhanced flux and anti-fouling properties for membrane distillation of secondary effluent
2023, Separation and Purification TechnologyChloride removal from flue gas desulfurization wastewater through Friedel's salt precipitation method: A review
2023, Science of the Total Environment