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Optimization of Sludge Settling Performance in Polyacrylamide-Enhanced Ultra-High Lime-Aluminum Treatment of Reverse Osmosis Concentrate.

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Bibliographic Details
Title:	Optimization of Sludge Settling Performance in Polyacrylamide-Enhanced Ultra-High Lime-Aluminum Treatment of Reverse Osmosis Concentrate.
Authors:	Liao, Zhenliang^1,2 (AUTHOR), Lei, Ruixia¹ (AUTHOR), Yin, Jiali¹ (AUTHOR), Zhou, Bin¹ (AUTHOR), Xu, Minglei³ (AUTHOR), Wei, Zhiyu² (AUTHOR) weizhiyu@tongji.edu.cn
Source:	Water, Air & Soil Pollution. Jun2026, Vol. 237 Issue 11, p1-12. 12p.
Subject Terms:	Wastewater treatment, Flocculation, Sludge bulking, Industrial wastes, Sedimentation analysis, Chlorides, *Water treatment plants, Polyacrylamide
Abstract:	The ultra-high lime-aluminum (UHLA) process has been demonstrated to be highly effective for the removal of chloride ions (Cl⁻) from high-salinity wastewater. However, previous UHLA studies have primarily focused on reaction performance, while sludge settling behavior which is critical for solid–liquid separation efficiency and engineering applicability has received limited systematic investigation. In this study, the settling behavior of sludge generated during the UHLA treatment of reverse osmosis concentrate (ROC) from a steel plant was investigated. Polyacrylamide (PAM) was introduced as a conditioning agent to regulate floc structure and enhance solid–liquid separation. The effects of PAM type, dosage, and reaction temperature on sludge settling and Cl⁻ removal performance were comprehensively investigated. The findings were as follows: (1) PAM significantly improved sludge settleability, with anionic PAM (18–20 MDa) increasing the mean particle size from 8.77 μm to 24.71 μm, thereby accelerating settling velocity and enhancing floc stability. (2) Under optimized conditions (PAM dosage of 4.0 mg/g Ds, 30 °C), the sludge volume after 120 min (SV120) reached 66.9%, while the Cl⁻ removal efficiency was maintained at 76.3%. Overall, this study advances UHLA research from Cl⁻ removal performance to sludge behavior optimization and provides engineering-oriented guidance for improving solid–liquid separation in UHLA-based treatment of high-salinity wastewater. [ABSTRACT FROM AUTHOR]
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Database:	GreenFILE

Description
Abstract:	The ultra-high lime-aluminum (UHLA) process has been demonstrated to be highly effective for the removal of chloride ions (Cl⁻) from high-salinity wastewater. However, previous UHLA studies have primarily focused on reaction performance, while sludge settling behavior which is critical for solid–liquid separation efficiency and engineering applicability has received limited systematic investigation. In this study, the settling behavior of sludge generated during the UHLA treatment of reverse osmosis concentrate (ROC) from a steel plant was investigated. Polyacrylamide (PAM) was introduced as a conditioning agent to regulate floc structure and enhance solid–liquid separation. The effects of PAM type, dosage, and reaction temperature on sludge settling and Cl⁻ removal performance were comprehensively investigated. The findings were as follows: (1) PAM significantly improved sludge settleability, with anionic PAM (18–20 MDa) increasing the mean particle size from 8.77 μm to 24.71 μm, thereby accelerating settling velocity and enhancing floc stability. (2) Under optimized conditions (PAM dosage of 4.0 mg/g Ds, 30 °C), the sludge volume after 120 min (SV120) reached 66.9%, while the Cl⁻ removal efficiency was maintained at 76.3%. Overall, this study advances UHLA research from Cl⁻ removal performance to sludge behavior optimization and provides engineering-oriented guidance for improving solid–liquid separation in UHLA-based treatment of high-salinity wastewater. [ABSTRACT FROM AUTHOR]
ISSN:	00496979
DOI:	10.1007/s11270-026-09373-9