Screening and Filtering the Water We Use

Natural water is an increasing scare resource, the demand for water is continually rising, even as new and innovative ways to capture, conserve and recycle water are developed. 

Essential as it is for nearly all human endeavour, clean water is surprisingly difficult to come by without major interventions.  While UV, chemical and other treatments are required to ensure raw water is potable, by far the most common treatment ahead of any use is screening or filtration.

Water in rivers, lakes and streams and collected rainwater run-off seems pretty clean. But how clean the water is often a matter of perception or opinion, and this will be determined by the intended use for the water. It might be clean enough to swim in as it is, but not clean enough for use in a brewery.

Water in rivers, lakes and streams and collected rainwater run-off seems pretty clean. But how clean the water is often a matter of perception or opinion, and this will be determined by the intended use for the water. It might be clean enough to swim in as it is but not clean enough for use in a brewery.

Consider the journey for water being used for any purpose other than its natural progression through the Water Cycle.  The diagram below, courtesy of GRID-Arendal/Studio Atlantis, shows common uses and re-uses of water between abstraction from source to being returned to the environment. It is worth remembering that this fairly simple schematic can be re-iterated many times across a wide metropolitan area.

At every change of use, water is screened or filtered to some extent.

For example:

Agriculture

Water abstracted for livestock or for irrigation is screened to remove particulate and debris that might block cattle troughs, or irrigators.

Water Treatment Plant

Water is screened on intake to take out any debris, leaves weed etc ahead of further treatment

Waste Water Treatment

Coarse screening on the dirty water intake, finer screening of wash water to keep screens clear, removal of particulate and contaminants.

Commercial & Residential

Filtration for grey water systems, screening for water source heat pump systems, cooling water. 

Wildlife Protection

Human use of water resources directly affects our environment, natural habitats and wildlife.  Relatively recently, regulations have come into force in Europe and North America to protect fish stocks and eel populations in our waterways. Screening at intakes for cooling water, water treatment, irrigation and industrial use may now be subject to restrictions on intake velocity and on intake screen mesh size.

Water Monitoring

Water monitoring technology is evolving in tandem with the pressing need to understand the environmental consequences of our water use.  A concomitant strengthening of regulatory requirements for monitoring water quality has increased the amount of water sampling and analysis required across the whole urban water cycle.

Sampling equipment – especially wet chemistry analysis – requires constant sample water filtered enough to prevent damage to sensitive monitoring equipment but not so fine as to compromise the samples.

Screening and filtering water from initial abstraction to eventual disposal are critical activities, and bring with them constant challenges and difficulties.

Screens and filters will always be liable to clog. How soon this happens depends as much on the quality of water being screened and filtered as it does on the type of equipment used and its installation.  It is one of the oldest and least well resolved problems affecting people’s lives. It’s almost analogous with the human condition, Sisyphean in its inevitable repetition and seeming futility, as even the best filter systems will eventually block up. 

It costs to maintain and clear blocked screens and filters. The disruption to activities dependant on the flow of screened water costs time and money. 

Ensuring a continuous and uninterrupted flow of water is not always possible all the time. Innovations in water filtration and screening technology strive to keep pace with the ever-rising demand for water, the sustainable use of water and preservation of water quality. 

In recent years new technologies and materials have revolutionised fine filtration, the use of ceramics, carbon nano-tubes and advances in membrane technology have raised the bar in water purification. 

Dirty water screening and filtration has embraced AI to develop tech and systems that anticipate when screens may clog, increasing the efficacy of self-cleaning filters, saving water and energy.  New biodegradable materials and designs for filter elements also add to the sustainability of the industry, along with better monitoring, greener chemistry and greater water reclamation and re-use.

There is still much that can be done and no perfect solutions; we are fated to always unblock something, sometime, as long as we need clean water.