CGF EQUIVALENT VERTICAL FILTERS

This Table compares the available filter area of horizontal & vertical filters.

NOTES:

  • This table is intended as a comparative guide – if in any doubt, contact us for more specific information.
  • The nominated vertical filters are an approximation of the nearest equivalent to the MHS filter range.
  • The filter area of a vertical filter is calculated as A = Π R² (with R being the filter tank radius)

COMMENTS:

  • CGF’s vertical filters provide a wide range of available filter area.
  • In terms of cost (ie., $/m2 of filter area) the MHS series provides the best value for money.
  • Vertical filter have a greater media requirement & on this basis, provide a greater opportunity for dirt retention. .
  • Vertical & horizontal filters have different plant space requirements, with horizontal filters being more compact.

TANDEM FILTER CAPACITY (0.5m2 TO 7.0m2)

This table assumes that you have determined the plant flow required for a specific application. It also assumes that you have decided to use a tandem backwash system, with two filters arranged in parallel to “filter” at a flow rate of 21m3/hr/m2. In this case, the filters are individually backwashed with the full duty of the pump to achieve the required backwash rate of 42m3/hr/m2.

NOTES:-

  1. The nominated backwash flow (in l/sec) is based on a backwash rate of 42m3/hr/m2. Subject to the type of filter media being used, this rate may vary.
  2. Pumping equipment should be selected to provide the required “backwash flow”.
  3. Filters with up to 3.5m2 of filter area may use single lever multiport valves; larger systems use commercially available valves arranged as either, a four or five valve matrix
  4. Larger plant capacities can be satisfied by using a number of tandem systems. Alternatively, a multiple tank system using a shunt backwash method may be considered

VERTICAL FILTER CAPACITY (0.5m2 to 7.0m2) – USING A SHUNT BACKWASH METHOD

This Table assumes that you have already determined the plant flow required for a specific application. It also assumes that you have decided to use a shunt backwash method. In conjunction with an acceptable filter rate (in m3/hr/m2) look for the flow rate that you have selected, keeping in mind that the most cost effective selection will have the fewest number of filter vessels.

NOTES:-

  1. By using the minimum plant capacity filter rates as low as < 8.5m3/hr/m2 may be provided.
  2. The nominated backwash flow (in l/sec) is based on a backwash rate of 42m3/hr/m2. Subject to the type of filter media being used this rate may vary.
  3. To prevent preferential flow, the filter modules in a shunt backwash system should be backwashed sequentially. Extend the washwater consumption/filter to account for the total number of filters. Determine the size/capacity of the backwash detention tank, sludge lagoon, or washwater recovery system by making adequate allowances for plant over-run, freeboard, and accumulation of sludge.
  4. Minimum plant flow is based on the filter’s required backwash flow multiplied by 1.2. This ensures that the shunt backwash valve does not need to be fully closed to obtain the required backwash rate.
  5. Maximum plant flow is based on the number of filters minus one, times the filter area of one module, times 42.

HORIZONTAL FILTER CAPACITY (5.4m2 to 43.5m2) – USING A SHUNT BACKWASH METHOD

This Table assumes that you have already determined the plant flow required for a specific application. It also assumes that you have decided to use a shunt backwash method. In conjunction with a suitable filter rate (in m3/hr/m2) look for the flow rate that you have selected keeping in mind that the most cost effective selection will have the fewest number of filter vessels

NOTES:-

  1. By using the minimum plant capacity filter rates as low as < 8.5m3/hr/m2 may be provided.
  2. The nominated backwash flow (in l/sec) is based on a backwash rate of 42m3/hr/m2. Subject to the type of filter media being used this rate may vary.
  3. To prevent preferential flow, the filter modules in a shunt backwash system should be backwashed sequentially. Extend the washwater consumption/filter to account for the total number of filters. Determine the size/capacity of the backwash detention tank, sludge lagoon, or washwater recovery system by making adequate allowances for plant over-run, freeboard, and accumulation of sludge.
  4. Minimum plant flow is based on the filter’s required backwash flow multiplied by 1.2. This ensures that the shunt backwash valve does not need to be fully closed to obtain the required backwash rate.
  5. Maximum plant flow is based on the number of filters minus one, times the filter area of one module, times 42. 

SWIMMING POOL FILTER SELECTION

BRIEF OVERVIEW

Whilst swimming pool filters are selected according to a diverse number of pre-requisites (pool volume, bather load, pool type, turnover rate, filter rate, etc.,) the Designer’s first step is to ascertain the exact volume of water to be treated.

The next step is to establish the “recirculation rate” that is considered most appropriate for the application. In many cases, state-based health Departments will nominate a “turnover rate” that is deemed necessary for a specific type of swimming pool. In some cases, these assessments are based on pool usage and or water depth. The required turnover rate will vary, depending upon a State’s specific requirements. This variance can be significant and if in any doubt reference should be made to the applicable standards & guidelines.

In a practical sense, a final filter selection should consider the type of process treatment and the recirculation system that is to be provided. The contribution made by the selected process design has potential to affect the type and size of the required filter plant. Logically, a process treatment that includes some form of advanced oxidation (albeit a recognized ozone or UV process) may have a different filtration requirement to a system that relies purely on a traditional sanitizer. Equally a filter that operates with a conservative “filter rate” will provide a greater contribution than a filter which is operating at a fast filter rate.

Whilst general guidelines are useful, there is no substitute for the applied experience that can be obtained from other similar projects. If in any doubt, it is often best to obtain specialist advice. Ad hoc decisions or poorly conceived assumptions will have the potential to create serious problems that will affect water quality, operating costs and maintenance requirements.

SELECTION OF THE FILTER RATE

Whilst filters manufactured by CGF are hydraulically balanced for design rates of up to 42 m3/hr/m2, filtration efficiency (and dirt holding capacity) will generally increase, as the design rate decreases. In other words, slower sand filter rates will provide improved filtration efficiency.

Case history suggests that where low turnover rates are used, faster filter rates (up to 42 m3/hr/m2) are suitable for moderately loaded and seasonally used outdoor pools. Conversely, design rates as low as 20 m3/hr/m2 are often required for indoor pools that are subject year round use and regular shock loadings.

In heated applications, the exchange rate (from the body of bathers) would radically increase as the temperature rises. In such cases, additional filter area, slower filter rates, and or advanced oxidation should be considered as being almost mandatory requirements. In many cases, state based Health Standards or Guidelines do not recommend or nominate any specific filter rates.

DETERMINING THE REQUIRED FILTER AREA

When the “recirculation rate” and the “filter rate” are known, the required “filter area” can be determined by simple subdivision. For example, if the recirculation rate is 450m3/hr and the filter rate is 25m3/hr/m2, the required filter area is as follows:-

Having established the required filter area, the Designer should consider the number of filter models that would best suit the available plant space, the number of pumps that will be used, and the preferred method of backwash. Given the wide range of choice that exists within the CGF filter range, numerous options will be available. These can include a choice of vertical of horizontal filters.

OTHER IMPORTANT CONSIDERATIONS

Apart from the interpolation that is required to select the type and number of filters, the system designer has a further obligation to ensure that the selected filters are capable of being effectively backwashed. Whilst system flaws related to poor backwash conditions, may not be apparent upon start-up, failure to achieve the correct backwash flow will affect the long-term performance of any filter system.

SELECTION CHECK LIST

When selecting a swimming pool filter, consideration should be given to the following factors:-

  • The product’s service history in other similar applications – be wary of over-sized domestic filters & or commercial filters that have no clear or identifiable track record.
  • Place of Manufacture – be wary of imported equipment. Your filter will require future parts & service.
  • The total amount of filter area – logically, this is directly related to the performance that can be expected.
  • The required number of filter modules – this will be largely dictated by the system design.
  • Filter construction materials and their suitability – corrosive resistant materials should be mandatory.
  • Filter media requirements and their quantity – the type & quantity of media are related to filtration efficiency.
  • Proposed backwash method & backwash efficiency – no matter which method you select, it must work.
  • Capital and Life Cycle Costs – a low purchase cost is not always what it seems; do your sums carefully.
  • Available plant space – use a proper design service & make provision for future service & maintenance.
  • Pool system design and proposed process treatment – effective design can provide long-term benefits.
  • Installation requirements and ease of operation – are comprehensive written Instructions available?
  • Level of Operator involvement and the level of training required – is automation warranted?
  • Energy consumption and maintenance costs – consider the case history of other/similar projects.
  • The knowledge and experience of the installing contractor – there is no substitute for experience.
  • The availability of technical support and future spare parts – Australian-made makes good sense.

Chadson Granular Filters
Mechanical & Chemical Filtration for Swimming Pool Water, Industrial Process Treatment, & Waste Water Industries

TYPICAL SPECIFICATIONS

1.0 GENERAL DESCRIPTION

The fiberglass pressure filters specified herein shall be the medium to high rate type as manufactured by CGF or approved equal. The filter manufacturer shall be regularly engaged in the production of water filtration systems with a minimum of ten (10) years experience with the manufacture of fiberglass pressure filters.

The filter system for the ………………………………..shall comprise ………. only Model No …………… filters that provide a total filter area of …square meters. The filter system shall operate at a filter rate of……….m3/hr/m2.

Individual filter modules shall be arranged to backwash at a rate of not less than … m3/hr/m2. With a conventional “water-only” backwash, each filter shall require a reverse flow of not less than……..l/second. Each filter vessel shall consume up to …m3 of wash water in a normal four-minute backwash. The system/process design shall be sized to permit consecutive backwashing of individual filters. When specified filter vessels shall be air scoured at a rate of not less than 32 m3/hr/m2 at 0.35 bar.

2.0 FILTER VESSELS

Filters shall be manufactured from FRP materials in general accordance standard procedures that recognize BS-4994, DIN 18820, and AS-2634. Vessels shall be designed and individually pressure tested to a certified test pressure of ……kPa. (The standard test pressure is 350kPa)

Filter vessels shall be adequately supported with a
skirt or number of cradles that are resin bonded to the filter shell. Filters shall be installed on a flat concrete base or plinth that is provided by others. The service weight of the filter shall be …………kgs. The plan area of the support skirt/cradle shall not be less than ……….m2.

Model …………..shall feature ……….number of access hatches as detailed on relevant shop drawings. Tank fittings shall include kinetic air bleed/vacuum breaker, screened drain cock, gauge panel, DN…………flanged inlet/outlet nozzles & identification label. Other special fittings and or requirements shall be noted as an Addendum to these Specifications.

Filter vessels shall be fabricated from approved resins in accordance with a comprehensive plan that indicates the nominal thickness, the distribution of reinforcing fibers according to type, quantity, and arrangement of the surface layers, resin type and curing mode. This plan shall recognize the requirements of DIN 18820. Vessels shall be internally lined with an impervious layer to resist chemical attack & abrasion.

3.0 INTERNAL DISTRIBUTION SYSTEMS

Filter internals shall be manufactured from uPVC & ABS of adequate size to provide hydraulic balance in both the filter and the backwash cycle. All internal pipework shall be adequately supported and fixed within the filter to suit the intended water flow and the operating pressures.

The top distributor (overdrain) shall be arranged to disperse soiled water evenly over the filter bed and to collect all particulate matter and wash water during a backwash cycle. Distribution headers shall be fitted with patented FloModuLata’s™ and or calibrated sized nozzles. Headers with simple drilled holes shall not be accepted.

The underdrain system shall comprise all necessary uPVC headers and injection moulded laterals. Laterals shall be moulded from engineering plastic (ABS) with inward tapering V shaped openings that are in general accordance with DIN19605. Drilled or slotted pipe laterals shall not be accepted. The underdrain system shall be sized to provide an open area that relates to the cross sectional area of the filter’s inlet/outlet. Where applicable the underdrain system shall be fitted with patented FloModLata’s™. The top distributor and the underdrain system shall provide a parallel flow from influent to effluent whilst maintaining a level and effective filter bed.

4.0 FILTER FACE PLUMBING

Face plumbing shall be fabricated on-site or alternatively, it shall be manufactured in the workshop of an approved pipe fabricator. (Strike out whichever is not applicable). Shop fabricated piping shall be subject to trial assembly at the Filter Specifications, Continued.

manufacturing plant. The system shall be dismantled for shipping purposes into convenient sub assemblies to minimize site assembly. The piping system shall be manufactured from …………………. materials in accordance with……………………….. (Insert either project specifications or a relevant Standard).

Face plumbing connecting to the filter(s) shall be sized based on having a line velocity not exceeding 2.5 m/sec. All pipework and valves shall be suitably supported in accordance with accepted Industry practice.

Unless specified elsewhere, valves shall be uPVC butterfly type, with EPDM seat, and stainless steel shaft. All valves up to 200 diameters shall be lever operated; valves over 200 NB shall be gear operated.

When specified, individual filters shall be supplied with Chadson single lever multiport valves for backwash purposes. Alternatively, filters shall be equipped with a matrix of either four or five commercially available butterfly valves. (Strike out whichever is not applicable and note that Shunt type backwashing using clean filtered water is specified as an Option).

Backwashing shall be conducted manually, according to pressure differentials (shown on the filter gauge panel) or at determined time intervals that are established to suit the application. The backwash piping system shall include a sight glass for visual inspection of waste wash water.

5.0 FILTER MEDIA

The installing Contractor shall check each filters lateral system (for any transport damage) before placing any media. Filter medias shall be placed into the filter vessel by the installing Contractor. Filter media shall be as follows:-

Bottom (1st) Layer:-
Media Type, Grade, & Qty (kgs) …………………………

2nd Layer:-
Media Type, Grade, & Qty (kgs) …………………………

3rd Layer (if applicable):-
Media Type, Grade, & Qty (kgs) …………………………

Sand type medias shall consist of uniformly graded silica sand, free of all foreign material, limestone and clay. Media shall be manufactured to AWWA B100-89 Standard with a specific gravity of 2.65 and a uniformity coefficient not exceeding 1.5.

Filter media shall be leveled-out to provide a flat & total bed depth of not less than …………mm.

6.0 OPTIONS

6.1 SHUNT BACKWASH

In this option, the filter vessels shall be arranged to be individually backwashed with clean filtered water; in this arrangement, conventional reverse flow backwashing with soiled water is NOT acceptable. Shunt backwashing shall be provided in accordance with the filter manufacturer’s Instructions.

6.2 AUTOMATIC BACKWASH & CONTROL CONSOLE

If and where specified, the filter system shall be provided with all valves, controls, fittings, actuators, positioners, and accessories to automatically control the filter’s functions. Push button/manual initiation shall also be provided and all automatic valves must be capable of manual operation.

Automatic functioning of the backwash system shall be primarily initiated by a differential pressure differential signal with a secondary seven day/twenty four hour timer. Backwash system shall protected against excessive flow or fault via a fail-safe system that includes (but is not necessarily limited to) a timer lockout and “normally closed” valve operation. The backwash controller shall as manufactured by CGF (eg.,Elbatrol) and or approved equal

7.0 EXECUTION & QUALITY CONTROL

7.1 TECHNICAL DATA

Within seven days of an equipment Order the filter manufacturer shall provide a fully dimensioned outline of the specified filter. Allowance shall also be made to provide all necessary technical data (& printed Instructions) to assist the installing contractor with the supply and co-ordination of all associated services.

7.2 QUALITY CONTROL

The entire system shall be inspected prior to shipment to verify compliance with the fabrication drawings and the project/product requirements. Material & Pressure Test Certificates shall be collated with all necessary installation data.

7.3 DEMONSTRATION

Notwithstanding any contract obligations, the installing Contractor shall provide the services of a qualified technician to visit the jobsite after the installation of the filter system has been completed. The technician shall assist with the initial start-up and the plant commissioning, ensuring that correct backwash flows are established. Allowance shall also made to assist with any specific training that pertains to the filter’s operation & or maintenance.

VCF SERIES : VERTICAL COLUMN FILTER – PHYSICAL DATA

  • No “flow range” has been nominated on the basis that the VCF product range is commonly used
    for “chemical filtration” whereby the Empty Bed Contact Time (EBCT) is the operative factor.
  • Filter internals are designed to suit the application and or the process.
  • Filter connections are sized and detailed to suit the application and or the process.
  • FRP vessels are “contacted moulded” as a monolithic structure with reinforced entry & exit ports.
  • Standard Test Pressure is 350 kPa – higher test pressures are available upon request.
  • Model specific data sheets/sales outlines are available upon request.
  • Dimensions are not to be used for construction or installation, unless certified by CGF
  • Details may be subject to change without notice and are for reference only. 

VDF SERIES : VERTICAL DUAL MEDIA – PHYSICAL & TECHNICAL DETAILS

  • “Flow Range” is based on a design rate of 15 to 42 m3/hr/m2 – filter rates will vary according to application
  • Nominal backwash duration is 3 to 5 minutes – Refer to CGF for possible backwash methods and details.
  • “Filter Media” requirements are nominated for a dual media application with:-
        (a) Bottom Layer of Silica Sand – 600mm deep (0.7mm to 0.8mm with an SG of 2.65) and
    (b) Top Layer of Hydro-anthracite – 600mm deep (1.7mm to 2.0mm with an SG of 1.5)
    Other bed compositions (including mono sand) are possible with changes to the media requirements.
  • For filter beds greater than 1200mm deep – refer to Model No VCF filters
  • FRP vessels are “contacted moulded” as a monolithic structure with reinforced entry & exit ports.
  • Standard Test Pressure is 350kPa – higher test pressures are available.
  • Model specific data sheets/sales outlines are available upon request.
  • Dimensions are not to be used for construction or installation, unless certified for this purpose by CGF
  • Details may be subject to change without notice and are for reference only. 

VHT SERIES : VERTICAL HI-TECH FILTER – PHYSICAL & TECHNICAL DETAILS


  • “Flow Range” is based on a design rate of 15 to 42 m3/hr/m2 – filter rates will vary according to the application.
  • Nominal backwash duration is 4 minutes – Refer to CGF for possible backwash methods and details.
  • “Filter Media” requirements include a substrate layer providing lateral coverage.
  • Models VHT are suitable for dual media applications with bed depths of up to 1200mm.
  • FRP vessels are “contacted moulded” as a monolithic structure with reinforced entry & exit ports.
  • Design Pressure is 400kPa – higher test pressures & different models are available upon request.
  • Model specific data sheets/sales outlines are available upon request.
  • Dimensions are not to be used for construction or installation, unless certified by CGF
  • Details may be subject to change without notice and are for reference only.
MHS SERIES : HORIZONTAL SAND FILTER – PHYSICAL & TECHNICAL DETAILS


  • “Flow Range” is based on a design rate of 15 to 42 m3/hr/m2 – filter rates will vary according to application
  • Nominal backwash duration is 4 minutes – Refer to CGF for possible backwash methods and details.
  • “Filter Media” requirements include a substrate layer providing lateral coverage.
  • FRP vessels are “contacted moulded” as a monolithic structure with reinforced entry & exit ports.
  • Standard Test Pressure is 350kPa – higher test pressures are available.
  • Model specific data sheets/sales outlines are available upon request.
  • Dimensions are not to be used for construction or installation, unless certified for this purpose by CGF
  • Details may be subject to change without notice and are for reference only.