ASTM D3739-19 PDF

Full title and description

ASTM D3739-19 — Standard Practice for Calculation and Adjustment of the Langelier Saturation Index for Reverse Osmosis. This practice provides procedures to calculate the Langelier saturation index (LSI) for reverse osmosis (RO) concentrate streams and techniques to adjust or control the index to reduce the risk of calcium carbonate (CaCO3) scaling in RO systems.

Abstract

This practice describes how to compute the Langelier saturation index for RO concentrate from feedwater analyses and RO operating parameters (TDS, calcium, alkalinity, pH, temperature and recovery). It summarizes methods to lower the LSI (for example, lowering recovery, reducing calcium, altering alkalinity/CO2 ratio, or using antiscalants/crystal modifiers) and indicates applicability limits for concentrate total dissolved solids (TDS).

General information

• Status: Active.
• Publication date: July 1, 2019 (designation D3739−19).
• Publisher: ASTM International.
• ICS / categories: 13.060 — Water quality (standards for water and RO/membrane processes; ASTM Committee D19).
• Edition / version: D3739-19 (revises D3739-06(2010)).
• Number of pages: 4.

Scope

This practice covers calculation and adjustment of the Langelier saturation index specifically for the concentrate stream of reverse osmosis devices. It is intended to determine the need for CaCO3 scale control in the design and operation of RO installations and is applicable to concentrate streams with about 10 to 10 000 mg/L TDS (for higher TDS, see Practice D4582). The practice uses SI units as the standard.

Key topics and requirements

• Procedure to calculate LSI for RO concentrate from feedwater TDS, calcium, alkalinity, pH, temperature and system recovery.
• Applicability limits: typical concentrate TDS range 10–10 000 mg/L; alternative practice referenced for >10 000 mg/L (D4582).
• Adjustment techniques: reduce recovery, remove or precipitate calcium, alter alkalinity/CO2 ratio, or apply antiscalants/crystal modifiers.
• References to related test methods and terminology (examples: ASTM D511, D1067, D1129, D1293) used to obtain input parameters.
• Guidance on interpretation of positive/negative LSI (tendency to scale vs. dissolve) and operational implications for RO membranes.

Typical use and users

Primary users are water-treatment engineers, RO system designers and operators, membrane manufacturers and consultants, and laboratory analysts who perform feedwater characterization and scale-control assessments. The practice is used during design, pretreatment selection, operational planning and troubleshooting of RO systems.

Related standards

Cross-references and related ASTM documents include Practice D4582 (for very high TDS concentrates), and various ASTM test methods and terminology used to measure pH, alkalinity, calcium and related parameters (for example D511, D1067, D1293, D1129). The practice is maintained under ASTM Committee D19 (Water).

Keywords

Langelier saturation index; LSI; reverse osmosis; RO concentrate; scale control; calcium carbonate; CaCO3; antiscalant; total dissolved solids; water treatment; membrane scaling.

FAQ

Q: What is this standard?

A: ASTM D3739-19 is a practice that defines how to calculate and adjust the Langelier saturation index for reverse osmosis concentrate streams to assess and control calcium carbonate scaling risk.

Q: What does it cover?

A: It covers calculation of LSI for RO concentrates from measured feedwater parameters and RO operating data, applicability limits (typically 10–10 000 mg/L TDS), and practical adjustment methods including operational changes and chemical scale inhibitors.

Q: Who typically uses it?

A: RO designers and operators, water-treatment engineers, membrane manufacturers, and laboratories performing water analyses and pretreatment evaluations.

Q: Is it current or superseded?

A: The current designation is D3739-19 (approved July 1, 2019). It revises and replaces the prior D3739-06(2010) edition. The document is listed as active as of the 2019 edition.

Q: Is it part of a series?

A: It is maintained under ASTM Committee D19 (Water) and is related to other D19 practices and test methods addressing membrane processes and water chemistry (for example D4582 and multiple water analysis methods referenced within the practice).

Q: What are the key keywords?

A: Langelier saturation index (LSI), reverse osmosis (RO), scaling, calcium carbonate, antiscalant, concentrate stream, total dissolved solids (TDS).