Process Refractometers for Water Treatment Chemical Concentration Monitoring

INTRODUCTION

Pure water treatment removes undesirable chemicals, biological contaminants, suspended solids, and gases from raw water. Water purification aims to produce water for a specific purpose, such as human consumption and medical or industrial use.

Polyaluminium coagulants are increasing use in potable water treatment plants, particularly for soft, colored surface waters. Polyaluminium chloride (PACl) is gradually replacing Alum (aluminum sulfate), a commonly used coagulant in water treatment plants. Alum coagulates at a limited pH range (between 5.5 and 6.5) and often requires alkali to the raw water to achieve the optimum coagulation pH. Furthermore, the alum floc produced is particularly fragile, which is vital if a coagulant is required to maximize color removal in a microfiltration-based water treatment process.

APPLICATION

Water treatment by chemical precipitation is a complex process. It starts with adding flocculants, specifically, Polyaluminium Chloride (PACl) and Sodium Hydroxide (NaOH). PACl is a synthetic polymer dissolved in water. It precipitates in big volumetric flocs, which absorb suspended pollutants in the raw water. The turbidity of the raw water defines Polyaluminium Chloride quantity. PACl concentration must be higher than 10 % To keep the flocculation process smooth. Polyaluminium Chloride is stable in the storage tank; however, it tends to crystallize after some time. Vaisala K-PATENTS® refractometer monitors the concentration of PACl to inform about the need for tank or pipe cleaning, thus preventing blockage caused by the PACl crystals.

NaOH regulates pH level, increases alkalinity, and neutralizes acids in the water. In alkaline water, the coagulation and flocculation processes work more effectively. Moreover, sufficient alkalinity prevents dissolving the lead from pipes and pipe fittings and reduces the corrosive effect of the water to iron pipes.

Further, particles suspended in water start to precipitate and agglomerate to form larger particles, known as flocs. The flocs are then settled at the bottom, forming sludge, and then removed from the process. After separating most of the floc, the remaining suspended particles and unsettled floc get filtered to remove water.

In the filtration phase, the water goes through the layers of anthracite, sand, and gravel. As a result, organic compounds contributing to taste and odor get removed. Other remaining particles get trapped by adhering to the sand and gravel particles.

After harmful micro-organisms get removed through filtering, it is necessary to add disinfecting chemicals to the water to inactivate any remaining pathogens and potentially harmful micro-organisms. One of the disinfecting chemicals used is Sodium Hypochlorite (NaOCl). When dissolved in water, this chemical releases chlorine, which is an efficient and safe disinfectant if added in a sufficient amount. Apart from sodium hypochlorite, liquid chlorine and chlorine dioxide are also choices as disinfectants.

Fluoride may also be added to the water to reduce tooth decay and prevent chronic diseases. However, fluoride in the water must not exceed recommended levels. Excessive levels of fluoride can be toxic or cause undesirable cosmetic effects such as staining of teeth.

Sodium Hypochlorite is unstable and quickly decomposes. The stability of NaOCl solution is dependent on the following factors:

• Hypochlorite concentration
• The temperature of the solution
• PH value of the solution
• The concentration of the impurities during catalyzing decomposition
• Exposure to light

With the process refractometer, it is possible to monitor NaOCl concentration and control the disinfection conditions.

The water purification disinfection stage happens in the disinfectant basin. Then, corrosion control assures the high quality of the purified water. Finally, the pure water gets stored for further consumption.

INSTRUMENTATION AND INSTALLATION

Vaisala K-PATENTS® Teflon Body Refractometer PR-23-M provides in-line measurements of Polyaluminium Chloride and Sodium Hydroxide at the initial stage of purification, ensuring the efficient flocculation of undesired particles. In addition, through the measurement of Sodium Hypochlorite and Fluoride at the water disinfection stage, high-quality purified water at the outlet is assured.

Refractometer installations happen in three different points in a by-pass loop between each chemical tank pump outlet and the treatment point. The refractometer allows monitoring the chemicals concentration at the exit from the storage tank to the pipe treatment point.

Typical measurement ranges are:

• PACl is ca. 10-11 %
• NaOH is ca. 40-45 %
• NaOCl is ca. 8-12 %

Miller Energy, Inc.
https://millerenergy.com
800-631-5454

The Vaisala K-PATENTS PR-43A Sanitary Process Refractometers for Food, Beverage & Dairy Industries

Vaisala K-PATENTS® Sanitary Process Refractometers PR-43-AC for hygienic installations in small pipe line sizes of 2.5 inch and smaller; PR-43-AP for hygienic installations in large pipes, tanks, cookers, crystallizers and kettles and for higher temperatures up to 150°C (300 °F); and the PR-43-APT for flush mounting installations in cookers, cooling crystallizers and other vessels that have scrapers or mixers.

Sanitary Refractometer Applications:

Extraction, evaporation, brewing, distilling, sugar dissolving, blending, filling. Alcohol, rum, whiskey, brandy, vodka, molasses, liquors, cider, alcoholic beverages, pre-mixed liquors. Beer and malt beverages, wort, cut beer, root beer. Juices, blended vegetable and fruit juices and nectars, still drinks, vegetable and juice concentrates, iced tea and coffee, instant coffee and tea. Soft drinks, energy and sport drinks, beverage base. Wines, grape must.

Sanitary Refractometer 3A Approval:

The Sanitary refractometer PR-43-A is Sanitary 3-A approved to meet the highest hygiene requirements of food production. The 3-A Symbol assures that the Sanitary Refractometer

PR-43-A conforms to 3-A Sanitary Standard Number 46-04 for Refractometers and Energy-Absorbing Optical Sensors for Milk and Milk Products and it has passed the independent Third Party Verification inspection for 3-A Symbol authorization.

For more information about Vaisala K-PATENTS products in Metro New York, New Jersey, Pennsylvania, Delaware, and Northern Ohio contact Miller Energy, Inc. Call them at 800-631-5454 or visit their web site at https://millerenergy.com.

Industrial Refractometers Used in Process Control

Refractometer for pharmaceutical use (K-Patents).

Part physics, part material science and part chemistry, refractometry is the process which measures the composition of known substances by means of calculating their respective refractive indexes (RI). RIs are evaluated via a refractometer, a device which measures the curve, or refraction, resulting when the wavelength of light moves from the air into and through a tested substance. The unitless number given by the refractometer, usually between 1.3000 and 1.7000, is the RI. The composition of substances is then determined when the RI is compared to a standard curve specific to the material of the substance.

Process refractometers provide the analysis to quickly, reliably, and very accurately identify a sample and determine it's concentration and purity levels. They measure the refractive index and temperature of flowing liquids, and apply mathematical functions to determine the concentration of dissolved solids.

Common industrial refractometer applications are:

• Calculating beverages’ amount of sugar dissolved is water.
• In commercial food applications such as juice production or tomato processing, refractometers are used to measure degrees Brix (Tthe Brix scale relates refractive index to sugar concentration, and is a key way to maintain consistency).
• In the pharmaceutical industry, process refractometers are used to monitor and control concentration levels during supersaturation, a critical process in crystallization.
• In pulp and paper production, process refractometers for measuring dissolved solids in black and green liquor during the chemical recovery process.

Equipment manufacturers have developed numerous refractometer configurations tailored to specific each use and application. Each has a set of features making it the advantageous choice for its intended application. Product specialists can be invaluable sources of information and assistance to potential refractometer users seeking to match the best equipment to their application or process.

For more information on industrial refractometers, contact Miller Energy by visiting https://millerenergy.com or by calling 908-755-6700 in New Jersey or 610-363-6200 in Pennsylvania.