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Water Monitoring

Water quality can be assessed in a number of different ways in terms of both physical and chemical contamination.

Physical contamination of water can include suspended solids and a characteristic known as total filterable matter, and generally refers to solid material present in the water sample. 

Chemical purity of water is assessed for a wide variety of different chemicals depending on the type of water and applicable local legislation. 

Chemical analysis of water can include testing for nitrogen compounds, dissolved heavy metals, and total and dissolved organic carbon.

Common water monitoring applications include:

  • Determination of suspended solids in water using for example glass fiber filters.
  • Chemical analyses of for example heavy metals, dissolved organic carbons (DOC), and ions.
  • Microbiological analyses using membrane based microfiltration methods
Suspended Solids Determination Chemical Analysis Bacteria Count and/or Detection

Suspended solids is a term used to describe the physical material in a water sample that will not settle. The level of suspended solids is generally assessed by a filtration-based method.

In general, suspended solids of a water sample is determined by pouring a carefully measured volume of water through a preweighed filter with a specified pore size, drying the filter to remove the water, and then weighing the filter again. The weight gain of the filter is a dry weight measure of the particulates present in the water sample expressed in units derived or calculated from the volume of water filtered (typically milligrams per litre).

Filters for Suspended Solids Analysis

Filters for suspended solids measurements are typically glass fibre filter circles, which the user needs to wash and weigh prior to use. However, GE Healthcare has developed ready-to-use 934-AH RTU glass fibre filters, which are supplied in a prewashed and pre-weighed format and enable considerable time-saving in the laboratory.

Chemical analysis of water is carried out to identify and quantify the chemical components and properties of groundwater, surface waters, sampling wells, and discharge waters from industrial operations (for example  factories and mines).

Some examples of chemical compounds commonly tested during water quality analysis include:

  • Dissolved heavy metals: Analysis of dissolved heavy metals such as lead (Pb) and mercury (Hg) in water samples is of importance due to the potential harmful effect on health and environment.
  • Total and dissolved organic carbon (DOC): DOC is generally defined as the organic matter that is able to pass through a filter, typically a 0.45 µm filter such as Puradisc Aqua 30.
  • Nitrite, nitrate and ammonia levels

 

Depending on the element or chemical compound being studied, different methods are applied to determine the quantities or ratios of the components. While some methods can be performed with standard laboratory equipment, others require advanced instruments, such as HPLC or inductively coupled plasma mass spectrometry (ICP-MS).

Filters for Chemical Analysis of Water

Filtration of the sample is usually required to remove particles which could interfere with the analysis or damage the instrumentation. Filter choice is important in order to ensure that the filter does not interfere with the test results. The filtration step is usually performed with syringe filters or syringe-less filters/filter vials.

When the sample is hard to filter, we recommend the use of a syringe filter that contains a prefilter in addition to the filtration membrane (GD/X or GD/XP syringe filters). It enables the filtration of larger sample volumes compared to filters without prefilters.

In the  specific case of heavy metal analysis, we recommend using a polypropylene pre-filter to minimize ionic extractable (GD/XP syringe filter).

Bacteria count and detection

The presence of microorganisms in the environment constitutes a potential risk to human health. Detection and quantification of specific organisms are used to evaluate the quality of water for human consumption, water for recreation, and waste water released into the environment after treatment.

Microorganisms in a water sample are collected using a microfiltration membrane filter. The membrane can then be transferred onto a microbiological culture medium for further identification and/or quantification of microorganisms.

Membrane filtration methods are commonly used for the detection of microorganisms such as E.coli, Clostridia, fecal coliforms, Legionella, Staphylococci, and Pseudomonas aeruginosa. These methods involve the use of membrane filters and filtration manifolds.

Membrane Filters for Microbiological Analysis of Water

The appropriate membrane filter choice will depend on the methodology being followed. The following membrane materials are most commonly used for microbiological analysis of water:

Membrane Material GE Healthcare Product
Mixed cellulose ester ME sterile membrane filters
Cellulose nitrate Microplus sterile membrane filters
Polycarbonate Nuclepore or Cyclopore membrane filters
Nylon NL membrane filters

 

Some membranes are supplied in STL format specific for use in membrane dispensers such as GE Healthcare’s Membrane-Butler. Membrane-Butler enables minimized cross-contamination risks and easy dispensing of the membrane filters.

Gridded membrane

Gridded membrane.

Membrane dispenser

Membrane dispenser.

Two-place filtration manifold with 350 ml filtration funnel

Two-place filtration manifold
with 350 ml filtration funnel.

Whatman AS200 Manifold of MBSI Microbiological Filtration System:

This system is a two place filtration manifold to be used with 100ml or 350ml GE MBSI filtration funnels.
Polypropylene version of these filtration funnels can be autoclaved up-to 50 times enabling consumable cost savings.

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