Water and Environment Sector: Single-Parameter Online Analyzers in Drinking Water Treatment Processes

Water, one of the essential sources of life, can contain not only vital minerals and nutritive elements but also harmful contaminants that undergo bioaccumulation. Contamination from heavy metals, fertilizers, pesticides, hormones, and similar substances that may occur during collection and storage of water from underground or surface sources poses high health risks. The World Health Organization (WHO) has published regulations concerning concentration limits containing approximately 200 different analytical parameters to eliminate the aforementioned health risks. These parameter limits, monitored with strict rules worldwide, vary according to the hydrogeological structure of the relevant geography where analyses are conducted. Continuous monitoring of analytical parameters is of great importance in preventing problems that could impede industrial processes. For example, through analyses performed during disinfection of drinking water, it is possible to eliminate by-products that may arise. Within this framework, the need for online measurement systems offering affordable, easy-to-use and integrated solutions for parameters that must be continuously monitored during the drinking water treatment process is increasing. [caption id="attachment_123043" align="aligncenter"] Figure 1. Drinking water treatment facility[/caption]  

Typical Drinking Water Treatment Process Steps

The design of a drinking water treatment facility depends on the quality and composition of the source water, but typically consists, in order, of: raw water inlet, coagulation/flocculation, sedimentation, filtration, disinfection, corrosion control and distribution steps. Prior to the main process, depending on source water conditions, some pre-treatment steps (screening, pre-settling, etc.) may also be added following raw water inlet.

Coagulation and Flocculation

In coagulation/flocculation processes, the objective is to accumulate and settle suspended particles in water to increase the efficiency of the subsequent sedimentation step. These particles with weak settling properties are smaller than 1 µm in size and are referred to as colloids. Among these colloids, which affect water color and turbidity, are clays, metal oxides, proteins, microorganisms and organic matter that can impart brown color to water. The common characteristic of colloids is that they carry a negative charge that prevents them from settling and being precipitated in still water. Colloids are agglomerated through the addition of chemicals bearing opposite (positive) charges, referred to as coagulants. While typical coagulants are in the form of aluminum and iron salts containing Al³⁺ and Fe³⁺ ions, in current facilities iron(III) salts are predominantly preferred. These coagulants with positive charge neutralize colloids with opposite charge, enabling particle agglomeration and thus forming insoluble hydroxides in the presence of high salt concentration and sufficient alkalinity. Deposits called floc formed together with coagulation combine with other small particles, transforming into larger mass deposits and are settled in the sedimentation step. [caption id="attachment_123044" align="aligncenter"] Figure 2. Sedimentation basin[/caption]

Sedimentation

Sedimentation is the settling of suspended particles with the aid of gravity and their separation from the water column. In this stage, long retention times and various tank mechanisms enable the floc to settle to a certain depth. While floc formation at the basin bottom is settled, clear water is extracted from the top layer. With the settling of floc, the sludge layer formed at the basin bottom contains coagulant, colloids from organic and inorganic sources and, where present, bacteria, viruses and protozoa. After sludge is removed from the basin bottom, it is processed to remove water and some solids.

Filtration

During filtration, partially treated water is passed through a porous medium consisting of sand or anthracite to remove fine organic and inorganic particles that could not be removed by sedimentation. Floc or suspended solids that may be present in the water passing through the filter are strained by adhering to the porous medium of the filter or interacting with other adsorbed particles. [caption id="attachment_123045" align="aligncenter"] Figure 3. Rapid gravity sand filter[/caption]   Filtration is quite a complex process both in terms of the type of filter used (simple slow sand or rapid gravity sand combinations) and the types of actions occurring (e.g., biological).

Disinfection

Before water distribution to the network, disinfection treatment must be applied to remove pathogenic microorganisms present at sizes invisible to the naked eye. Chlorine is the most popular disinfectant used due to its effectiveness at low concentrations, low cost and the residual it leaves that indicates the efficiency of the disinfection application. [caption id="attachment_123046" align="aligncenter"] Figure 4. Water disinfection with chlorine[/caption]   Chlorine use has certain disadvantages. The presence of organic matter in water to which disinfection is applied can lead to the formation of carcinogenic by-products (DBP, trihalomethanes) that may pose a health threat. Many studies have observed the highest trihalomethane concentrations at alkaline pH values. In our country, the trihalomethane limit value in TSE-266 drinking water quality standards has been set at 100 µg/L. Chlorine also reacts with ammonia to form chloramines, which are disinfectant substances. Although chloramines do not have as high disinfection effectiveness as chlorine, they have a much lower likelihood of producing bad taste and odor and are more durable for longer periods than free chlorine. The recently widespread use of ozone (O₃) is effective against viruses and spores and does not cause by-product formation such as trihalomethanes. On the other hand, ozonation can produce toxic bromates, especially if bromine is present in water, and also does not provide a residual level like chlorine for protection during distribution. For this reason, water that has undergone ozonation is chlorinated before entering the supply system.

Analytical Parameters

Monitoring and continuous tracking of critical parameters in drinking water treatment processes is vital for the sustainability of the water quality obtained and public health. Within this framework, close monitoring is foreseen to ensure that these analytical parameters, each making a specific contribution to each stage of the treatment process, comply with standard conditions established in regulations:

Trace Heavy Metals

Heavy metals at ppb levels in water pose a danger to human health. Therefore, analysis of total arsenic and toxic metals (Hg, Ni, Co, Cu, Cd, Pb, Cr, Zn, Sb) is vital.

pH

Both control of the raw water entering the facility and achieving optimum pH for efficient coagulation process are vital. In addition to this, the effectiveness of active chlorine in water during disinfection and the formation of trihalomethane by-products are also related to the pH of water.

Ammonia

Ammonia levels monitored in raw water at facility inlets can be an indicator of contamination events resulting from agricultural waste runoff and seepage.

Iron/Aluminum

Verification and monitoring of aluminum or iron salt levels in coagulant chemical dosing used during the treatment process to remove and settle metals, organics and other unwanted compounds in water is an important quality parameter.

Manganese

High manganese impurities in water can cause serious color changes in drinking water.

Hardness

Hardness at ppm levels can cause serious scale and deposit formation in pipes. Monitoring of water hardness is important to prevent such damage.

Fluoride

Some drinking water facilities dose drinking water with fluoride to prevent dental problems for end users.

Chlorine

Chlorination of drinking water is important for disinfection and keeping water free from microbial growth. Chlorine level must not exceed the limits established in regulations to protect human health. [caption id="attachment_123047" align="aligncenter"] Figure 5. Analysis points in drinking water treatment process[/caption]  

Ammonia/Chloramination Monitoring

Chloramination stands out as a disinfection strategy frequently used in present-day drinking water networks that is more durable and produces fewer health-hazardous by-products. On the other hand, chloramination of drinking water requires large amounts of free ammonia. However, monitoring and control of free ammonia level in the chloramination process is quite important to ensure that free ammonia amount does not exceed allowed limits.

Phosphate

Phosphate dosing is important for protecting pipe networks from corrosion and also for preventing the dissolution of toxic lead in drinking water. Very high phosphate levels are a separate health risk and therefore must be closely monitored.

Online Analysis in Drinking Water Treatment Processes

Problems occurring in manual sampling or manual analysis processes for critical parameter analysis in drinking water treatment processes can result in significant production quality and time losses. Considering all factors stemming from potential errors such as operator differences, experience level, sample volume taken, equipment/accessory cleanliness, analysis frequency, etc., the advantages that an online analysis platform capable of enabling automatic sampling, fully automatic analysis, result reporting and alarm transfer steps at out-of-limit values become clearly apparent. Parameter measurements are performed through automatic sampling of the sample and completion of all subsequent analytical processes without requiring any intervention. Through automatic transfer of obtained analysis results to PLC controller systems and the ease of remotely controlling the analyzer, rapid intervention in the process is enabled, providing significant advantages within this framework. As Metrohm, within the framework of the rich application portfolio that forms the basis of our global leadership position in titration and the experience, knowledge accumulation and expertise we have gained in process analysis to date, we present to you our fully automatic 202X Series Single-Method Online Analyzer systems suitable for the Industry 4.0 generation for water treatment facilities. With advantages such as continuous operability, low chemical consumption, reliable 24/7 operation and user-friendly graphical interface, the 202X Series Single-Method Online Analyzer systems guarantee reliable process monitoring and control while enabling you to save time and cost. The 202X Series Single-Method Online Analyzer systems are grouped under two main hardware segments. For measurements based on potentiometric and ISE analysis techniques, the 2026 Online Titrolyzer: [caption id="attachment_123048" align="aligncenter"] Figure 6. 2026 Online Titrolyzer[/caption] For measurements based on photometric and colorimetric analysis techniques, the 2029 Online Photometer: [caption id="attachment_123049" align="aligncenter"] Figure 7. 2029 Online Photometer[/caption]  

Both system variants feature striking common characteristics:

• Compact footprint that saves floor space for narrow industrial areas. • IP66-compliant secure and sturdy external housing. • Proven applications across various sectors over a wide range, directly validated in the field. • Remote access/control capability via ethernet, Modbus TCP/IP and USB data transfer. • System management and trend graphs through a 7" full-color touchscreen. Standard Equipment Sets. The 202X Series Single-Method Online Analyzer systems are presented as analyzer equipment sets with various standard system components for analysis and control of parameters present in drinking water treatment processes:

Sampling

In 202X Series Single-Method Online Analyzer systems, the sample is conveyed directly via a closed sampling line to the reaction vessel. Thus, unlike manual sampling, a representative sample from the correct sampling point that does not come into contact with the external environment reaches the analyzer. With the 202X system, it is possible to perform sampling from either a single or two different sample flow points.

Reliable Analysis Results

Accurate and repeatable results obtained from measurements conducted using the 202X Series Single-Method Online Analyzer systems demonstrate that the systems can be successfully integrated into each stage of the water treatment facility. The fully automated nature of the system brings numerous advantages. Compared to manual analysis, fully automatic online analysis can prevent errors such as incorrect sampling, failure to identify measurement points, and incorrect and non-repeatable results. Since all procedures such as sample collection, chemical additions, analysis step and result recording are automatically provided under the 202X system framework, measurement errors, differences between operators and analysis time inconsistencies are eliminated, and through continuous hands-off analysis, labor requirements decrease while operator safety increases. As parameter measurements become more accurate, precise and efficient, malfunctions that may occur in the process can be monitored in real time, quality increases are obtained and production rework problems are minimized. The 202X Series Single-Method Online Analyzer systems transfer all data such as ongoing analyses, obtained results, alarms, etc. to PLC or other data systems as requested, via digital/4-20 mA analog outputs, Modbus TCP or transmission infrastructures such as VNC available on the equipment, enabling continuous monitoring of the process and immediate intervention if any disruption occurs.

Complete Drinking Water Treatment Process Monitoring

The 202X Series Single-Method Online Analyzer systems form single-parameter entry-level systems for different operation steps in the water treatment process. When multiple parameters are desired to be measured together in the treatment facility or when analysis frequency or measurement points are to be increased, we offer higher-level models such as the 2035 or 2060 Process Analyzers, providing comprehensive combinations (Figure 8). [caption id="attachment_123051" align="aligncenter"] Figure 8. 2060 Online Process Analyzer[/caption]   In addition to the parameters measured with 202X systems, online voltammetric analysis of heavy metals (Hg, Ni, Co, Cu, Cd, Pb, Cr, Zn, Sb) can be performed with the 2045VA Online Process Analyzer. Metrohm Process Analytics has over 40 years of experience in online process analysis worldwide. In drinking water treatment facilities, we continue to serve our customers reliably with our equipment fleet of more than 153 installed analyzer systems in the EMEA region alone and to offer our global expertise in the sector. As the Metrohm Turkey Process Analytics Team, we can provide comprehensive services ranging from project consultation, engineering and sales phases to analyzer installation, commissioning and training, system maintenance, accessories and spare parts supply, support, service and repair processes. Through our local organization working in integration with the Metrohm Process Analytics EMEA Regional Center, we are by your side for all your online analysis needs.

Sources 1) 80005233EN 2026 Titrolyzer/2029 Process Photometer – Powerful and compact single method online analyzers 2) 80005XXXXEN Metrohm Process Analytics – Online Analyzers for Potable Water Processing 3) Open Learn Free Courses - Potable water treatment. (2012, August 10). Retrieved December 15, 2020, from https://www.open.edu/openlearn/science-mathstechnology/engineering-and-technology/technology/ potable-water-treatment/content-section-0?activetab=description-tab 4) Lisle, J. (2000). Drinking Water Treatment and Regulations in the United States. Laboratory Medicine. 31(9): 492-496