User:GeoChemStud/Analysis of water chemistry

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Water chemistry analyses provide information on the composition and properties of a given water sample. Techniques and the extent of analysis is dependent upon the nature of the water sample and the purpose of the analysis. A chemical analysis can be used to determine the profile of chemicals in water that might serve as a municipal drinking water supply. Wastewater produced by industries and other facilities are also subjected to analytical testing, which may be mandated by particular regulatory and government entities and/or legislation. Other laboratories utilize water analysis techniques for basic research purposes, such as hydrology, sedimentology, and geochemistry. Depending upon the particular requirements for an analysis, the equipment and methods being employed can vary and span across multiple areas of analytical chemistry and biology.

Drinking Water Quality

Surface or ground water used for a drinking water supply must meet rigorous chemical standards following treatment. This requires detailed knowledge of the water entering the treatment plant. In addition to the normal suite of environmental chemical parameters, other parameters such as hardness, phenol, oil, and in some cases, a real-time organic profile of the incoming water is needed, as in the River Dee regulation scheme.

Performing analysis to determine the quality of drinking often calls for sampling that would be representative of for the multiple stages of treatment and transport of the water to the consumer.

In industrial process, the control of the quality of process water can be critical to the quality of the end product. Water is often used as a carrier of reagents and the loss of reagent to product must be continuously monitored to ensure that correct replacement rate. Parameters measured relate specifically to the process in use and to any of the expected contaminants that may arise as by-products. This may include unwanted organic chemicals appearing in an inorganic chemical process through contamination with oils and greases from machinery. Monitoring the quality of the waste water discharged from industrial premises is a key factor in controlling and minimising pollution of the environment. In this application monitoring schemes analyse for all possible contaminants arising within the process and in addition contaminants that may have particularly adverse impacts on the environment such as cyanide and many organic species such as pesticides. In then nuclear industry analysis focuses on specific isotopes or elements of interest. Where the nuclear industry makes waste water discharges to rivers which have drinking water abstraction on them, radio-isotopes which could potentially be harmful or those with long half-lives such as tritium will form part of the routine monitoring suite.

Wastewater Regulatory Testing

Water samples from the natural environment are routinely collected and analyzed as part of a pre-determined monitoring program by authorities to ensure that waters remain uncontaminated, or if contaminated, that the levels of contamination are not increasing or are falling in line with an agreed remediation plan. An example of such a scheme is the harmonized monitoring scheme operated on all the major river systems in the UK. The parameters analysed will be highly dependent on nature of the local environment and/or the polluting sources in the area. In many cases the parameters will reflect the national and local water quality standards determined by law or other regulations. Typical parameters for ensuring that unpolluted surface waters remain within acceptable chemical standards include pH, major cations and anions including ammonia, nitrate, nitrite, phosphate, conductivity, phenol, chemical oxygen demand (COD) and biochemical oxygen demand (BOD).

Research

Many aspects of academic research and industrial research, such as in pharmaceuticals, health products, and many others, relies on accurate water analysis to identify substances of potential use, to refine those substances and to ensure that when they are manufactured for sale that the chemical composition remains consistent. The analytical methods used in these area can be very complex and may be specific to the process or area of research being conducted and may involve the use of bespoke analytical equipment.

In environmental management, water analysis is frequently deployed when contamination is suspected and when a pollutant needs to be identified if remedial action is taken. The analysis can often enable the contaminator to be identified. Such forensic work can examine the ratios of various components and can "type" samples of oils or other mixed organic contaminants to directly link the pollutant with the source. In drinking water supplies the cause of unacceptable quality can similarly be determined by carefully targeted chemical analysis of samples taken throughout the distribution system. In manufacturing, off-spec products may be directly tied back to unexpected changes in wet processing stages and analytical chemistry can identify which stages may be at fault and for what reason.

Methodology

A water analysis can range from measuring physicochemical properties, such as pH and temperature, to quantifying various species and contaminants, like dissolved solids and trace metals. The analysis performed on a given water sample can depend on the nature of the sample (i.e. sampling location) and the purpose for analysis. Often, method protocols are established by different organizations for consistency in analysis results.

These protocols can span across various laboratory techniques:

• Conventional Wet Chemistry: Water samples can be analyzed through benchtop methods like acidification and complexometric titration; other techniques involve preparation of a sample (e.g., filtration) to use with equipment such as microscopes.
• Microbiological Testing: There are a range of techniques that detect and quantify microorganisms that may be present in water. These testing methods can include membrane filtration and lactose fermentation.
• Electrochemistry: Various electrode-based equipment can measure water properties like pH, specific conductance, and dissolved oxygen; voltammetry also is included for measurements of select metal ions.
• Colorimetry/Spectrophotometry: Analytes often have unique optical properties that can be measured using techniques, such as atomic absorption spectroscopy (AAS) and inductively coupled plasma optical emission spectroscopy (ICP-OES).
• Chromatography: Chromatography methods use separation to detect and quantify chemical components, such as volatiles, organics, and anions. These techniques include the use of liquid chromatography (LC), gas chromatography (GC), and ion chromatography (IC).
• Mass Spectrometry: Mass spectrometry, such as inductively coupled plasma mass spectrometry (ICP-MS), is utilized to quantify metals in trace amounts such as arsenic, cadmium, and lead. Mass spectrometry is often used in conjunction with other techniques, such as chromatography.

In addition to laboratory techniques, some measurements are made in-field since some properties do not preserve after sampling and storage. The United States National Water-Quality Assessment Program outlines some of the properties that should be made on-site:

In-Field Measurements for Water Quality Assessment

Measurement	Equipment
Temperature	Thermistor
pH	pH meter/electrode
Alkalinity	Titrator, sulfuric acid
Specific conductance	Conductivity meter
Dissolved oxygen	Membrane-type electrode

After water samples are collected, the Environmental Protection Agency in the United States has a set of approved analytical methods that ensure compliance with the Clean Water Act. Similarly, the EPA also outlines methods to use to measure contaminants for drinking water samples.

Regulated Contaminants in Drinking Water

Class	Contaminant	Method
Microorganisms	Enterococci	Membrane filtration
	Escherichia coli	Membrane filtration
	Cryptosporidium	Filtration/Immunomagnetic separation/Immunofluorescence Assay Microscopy
	Giardia	Filtration/IMS/FA
	Total Coliforms	Lactose fermentation, membrane filtration, enzyme substrate
Disinfectants	Chloramines/Chlorine (as Cl2)	Colorimetry/Spectrophotometry
	Chlorine dioxide	Visible Spectrometry, Amperometry
Disinfection Byproducts	Bromate	IC
	Chlorite	IC, Amperometry
	Haloacetic Acids	GC, IC-ESI-MS/MS
	Total trihalomethanes	GC-MS
Inorganics	Various metals (Sb, As, Ba, Be, Cd, Cr, Cu, F, Pb, Hg, Se, Th)	ICP-OES, AAS, ICP-MS
	Asbestos	Transmission Electron Miscroscope
	Cyanide	Spectrophotometry
	Nitrate/nitrite	IC, Spectrophotometry
Radionuclides	Alpha particles	Evaporation/Co-precipitation/Scintillation Counting
	Beta particles and photon emitters	Evaporation/Scintillation Counting
	Radium-226	Radon Emanation
	Radium-228	Beta activity
	Uranium	Fluorometry, Phosphorimetry, ICP-MS,