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Cleaning of Mecana Pile Cloth Media Filters: Best Practice

There is considerable debate and no little confusion at present around the cleaning of Pile Cloth Media Filters (PCMF), the nature of what this cleaning constitutes and when it needs to occur.

When Mecana, the first and undoubtedly the best PCMF in terms of the number of installations worldwide and ultimate levels of performance, arrived on the market to challenge the established opposition e.g. sand filters, one of its main attractions was (and indeed still is), the low operating cost – installed power is low, the drum only rotates and the suction pumps only run when a backwash is actually needed.

In addition to the regular backwashes, it is recommended that occasionally the cloths are removed for a clean with a pressure washer, ideally every twelve months.  This not only keeps the cloth in tip-top condition and hence delivering the excellent effluent quality to which our customers have become accustomed, but also maximises their life expectancy, often well beyond the accepted 7½ years working life.

The annual cleaning procedure had been specially developed and is unique to Mecana; it involves a special attachment for a standard pressure washer which comes free with every contract (plus a support stand to hold the cloth segment while it is being cleaned), along with appropriate training and support.  As an alternative, the ELIQUO HYDROK Service and Maintenance Team, a dedicated group of specialists using a fleet of self-sufficient service vans, can undertake this cleaning process for the customer; an increasing number of customers are taking advantage of this professional service.

ELIQUO HYDROK Maintenance and Service team at a Mecana site for an annual PCMF clean.

It is notable that the source of water for this cleaning can often be the high-quality effluent produced by the Mecana installation itself.  If this is not possible then a suitable source of ‘site water’ can be utilised, or (and particularly for the smaller installations) the water and power for the pressure washer can be provided from the service van.  Further, the product of the pressure washing process can be discharged into the Mecana feed channel, which makes the whole process self-contained for the customer, very sustainable and planet friendly, as there is no waste product to dispose of.

Our Service and Maintenance Team also carry essential spares and thus can ensure a Mecana PCMF is always at its best.  When they undertake a clean they will also test and ‘MOT’ the whole filter free of charge, issuing a written report on the condition and items which may need attention either immediately, or within the next twelve months.  The added advantage of utilising this service is that it extends the standard warranty and guarantee, which many Mecana users consider to be of great value.

Pressure washing the Mecana PCMF filters using the bespoke cleaning stands and special cleaning head.

So ELIQUO HYDROK has no need for, and indeed are not proponents of, chemical cleaning as by definition it utilises chemicals which can be dangerous to store, handle, use and dispose of.  We are also sure, having thoroughly investigated for ourselves, that chemical cleaning not only signifies a lack of thought and consideration in the design and testing of a PCMF process, but that it is also economically unattractive for our customers, less sustainable and planet friendly.  In addition, we believe chemical cleaning does not actually solve the problem e.g. an elevated frequency of backwashing over time, because once an organism becomes established, even if it is ‘killed off’ intermittently i.e. by a chemical clean, it tends to return – again and again.

A chemical clean, of any sort, has therefore never been a requirement, nor a necessity, with Mecana filters.  This remains the case and is attributed to the unique OptifiberTM cloth used in Mecana installations.  OptifiberTM is a product of careful research, design, construction and development which has resulted in the testing of hundreds of different formulations (including the backing which acts as a foundation for the fibres) to produce a cloth with the optimum ability to filter and backwash.  This is borne out by the extensive list of operational plants across both the UK (with over 100 installations) and the world, with some operating successfully in the most demanding of applications e.g. primary treatment.

Mecana  OptifiberTM cloth for optimum filtering and backwash capability

It is true that ELIQUO HYDROK do offer a pile cloth media resistant to chlorine, a commonly used cleaning agent, but this has been developed for specific applications, including potable water treatment (where cleanliness is of prime importance and the ability to disinfect is essential) and those wastewater treatment installations (particularly in the United States) where chlorine disinfection is part of the treatment process.

As Lewis O’Brien, Technical Director puts it, “At ELIQUO HYDROK we could not be clearer, our Mecana Pile Cloth Media does not need chemical cleaning and we will not settle for an inferior cloth that requires regular chemical cleaning in an attempt to make up for inadequate backwash characteristics.  The OptifiberTM cloth we use has been thoroughly designed and constructed so as not to need a chemical clean.  We do however, recommend that if our Mecana units are to perform optimally and as intended throughout its projected, expected life, that the cloths are given a chemical free pressure wash clean once a year.”

Author: Geoff Cooper-Smith, November 2020.

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Dave Armstrong
Tel. +44 1726 862000