Sand Filters

9. Sand Filters

9.1 Design Standards

1. not be loaded in excess of 120 L per square metre (2.4 gallon per sq. ft.) per day, and
2. have an effective surface area of not less than 17 square metres (150 sq. ft.) when serving a single family dwelling.

1. not be loaded in excess of 50 L per square metre (1 gallon per sq. ft.) per day, and
2. have an effective surface area of not less than 34 square metres (360 sq. ft.) when serving a single family dwelling.

See Pg. 69, Table A.1.A. in Appendix "A"
See Pg. 138, Pressure Distribution Lateral Design in Appendix "B"

See Pg. 140, Squirt Test in Appendix "B"
See Pg. 204, Fig. SF 1 in Appendix "B"
See Pg. 205, Fig. SF 2 in Appendix "B"
See Pg. 206, Fig. SF 3 in Appendix "B"

See Pg. 69, Table A.1.A. in Appendix "A"

See Pg. 140, Squirt Test in Appendix "B"

Intent: Numerous light applications of effluent provide better treatment conditions. A timing device to control the pump is desirable to provide a wait period between each volume per flush and also to provide volumes per flush evenly spaced over a 24 hour day.

1. the location, design, and construction of the pump vault do not conflict with this Standard for the design, construction and operation of a sand filter,
2. the pump and related apparatus are housed in a corrosion resistant vault designed to
   1. withstand the stresses placed upon it,
   2. prevent the migration of drain media, sand, or underdrain media to its interior,
   3. provide watertight access to finished landscape grade with a diameter equal to that of the vault, and
   4. receive treated effluent from an elevation equal to that of a gravity discharging sand filter, and

3. the depth of underdrain media and the operating level of the pump cycle and alarm does not allow effluent within two inches of the bottom of the sand filter media.

See Pg. 203, Fig. Typical SF 1 in Appendix "B"

See Pg. 27, Article 3.3.1

1. detecting a high effluent level condition, and
2. delivering a visible and audible signal to alert the user of the system, the effluent level is above normal operating levels.

9.2 Installation Standards

1. 1.5 m (5 ft.) from a property line measured from the foot of the berm,
2. 15 m (50 ft.) from a water source,
3. 15 m (50 ft.) from a water course,
4. 9 m (30 ft.) from a basement or cellar, and
5. 3 m (10 ft.) from a building without a basement.

See Pg. 38, Article 7.1.6. for Vertical Separation Requirements.
See Pg. 178, Fig Vertical Separation in Appendix "B"

1. 1 m (3.25 ft.) from a property line measured from the foot of the berm,
2. 9 m (30 ft.) from a water course,
3. 9 m (30 ft.) from a water source, and
4. 1 m (3.25 ft.) from a building.

See Pg. 38, Article 7.1.6. for Vertical Separation Requirements.
See Pg. 178, Fig Vertical Separation in Appendix "B"

1. an underdrain pipe to collect effluent which shall
   1. be in the interior of the filter at the lowest elevation,
   2. be positioned with the saw cuts down, and
   3. be connected to a pump vault or extend beyond the edge of the sand filter using solid pipe to connect to a subsequent effluent disposal method,

   Intent: An underdrain pipe laid in the centre of the sand filter along the long axis quickly collects effluent.

2. a layer of media, containing the underdrain piping, to a minimum depth of 200 mm (8 in.) which shall be
   1. drain media in the lower 150 mm (6 in.), and
   2. underdrain media in the upper 50 mm (2 in.),

   
   

   Intent: The media immediately under the sand layer (underdrain media, which is pea gravel as specified in Article 9.3.7.) should be small enough to support the sand media. Below this supporting layer, the underdrain piping should be enveloped in a course drain media (larger sized rock, Article 9.3.6.) to provide less restriction of effluent flow into the underdrain piping. The layers below the sand must be well drained to ensure aerobic conditions in the sand above.

3. a minimum of 600 mm (2 ft.) of sand filter media installed over the underdrain media,
   1. where medium sand is used, the sand shall be damp at the time of installation, and
   2. the top surface of the media shall be level,

4. a pressurized distribution lateral system above the sand layer
   1. having distribution laterals installed in clean drain media that covers the orifice shields and extends a minimum of 75 mm (3 in.) below the distribution laterals, or
   2. installed in a chamber system,

5. a light filter fabric covering the top of the media or chamber system in which the pressure distribution lateral system is installed, and

6. a soil cover over the top of the intermittent sand filter area that is
   1. a depth of between 150 mm (6 in.) and 300 mm (1 ft.)
   2. a textural class no finer than loamy sand, and
   3. planted to grass or covered with a sod.

Intent: The soil covering the sand filter must be very course to allow a free flow of air into the sand filter.

Note: Grass cover must be established as soon as possible to prevent erosion of the soil cover.

See Pg. 205, Fig. SF 2 in Appendix "B"
See Pg. 206, Fig. SF 3 In Appendix "B"
See Pg. 159, Sand Filters in Appendix "B"

See Pg. 204, Fig. SF 1 in Appendix "B"

1. not smaller in diameter than 19 mm (¾ in.),
2. spaced at not more than 762 mm (30 in.) centre to centre, and
3. where chambers are used, provided in each chamber of a chamber system that
   1. is installed in accordance with the manufacturer's instructions,
   2. covers a minimum of 90% of the sand area, and
   3. is set on a minimum of 50 mm (2 in.) of drain media covering the sand layer.

1. not smaller than 3.2 mm ( in.),
2. not exceeding the maximum number of orifices specified per pipe size in Table A.1.A.,
3. sized to provide even distribution of effluent at a minimum of 1500 mm (5 ft.) pressure head supply pressure,
4. pointing upwards,

   Intent: Locating the orifice on the upper half of the pipe can help prevent clogging of the orifice by accumulated biological growths. Wherever the orifices are located, the orifices must be protected from rocks setting on the orifice and there must be room for the effluent to escape. The spraying effluent must not cause any erosion of the soil or sand around it.

5. protected by a device intended to prevent gravel from plugging the orifice and to encourage the distribution of effluent over a larger area, and
6. spaced such that there is one orifice for each
   1. 0.55 square metre (6 sq. ft.) of sand surface area in a medium sand filter, or
   2. 0.18 square metres (2 sq. ft.) of sand surface area in a course sand filter.
      
      

   Intent: Fine, even distribution of the effluent over the sand surface should provide better treatment by using the entire sand surface area and minimizes saturated flow.

See Pg. 69, Table A.1.A. in Appendix "A",
See Pg. 192, Fig. PDL 1 in Appendix "B"
See Pg. 193, Fig PDL 2 in Appendix "B"
See Pg. 194, PDL 3 Squirt Test in Appendix "B"
See Pg. 138, Pressure Distribution Lateral Design in Appendix "B"

See Pg. 194, PDL 3 Squirt Test in Appendix "B"

Intent: A vertical separation between the invert of the underdrain piping outlet and the disposal field trench must exist that will not allow effluent to back up into the sand filter base saturating the sand before surfacing over the disposal trench.

9.3 Requirements for Materials

1. smooth, rigid plastic piping, and
2. certified for a pressure application by a testing agency recognized by the Standards Council of Canada, or acceptable to an Administrator.

1. a reinforced concrete container,
2. constructed of materials other than concrete when equivalent performance and water tightness can be expected, or
3. a flexible membrane liner having properties that are at least equivalent to 0.762 mm or 762 µm thick (30 mil) unreinforced polyvinyl chloride (PVC).

1. in accordance with ASTM C-136, Standard Methods for Sieve Analysis of Fine and Coarse Aggregate, and in conjunction and accordance with ASTM C- 1 17, Standard Test Method for Materials Finer than No. 200 Sieve in Mineral Aggregates by Washing, and
2. performed by a qualified third party.

1. in a course sand filter, well washed sand consisting of the following particle size
   1. 100 percent passing the 3/8" sieve,
   2. 77 to 100 percent passing the No. 4 sieve,
   3. 53 to 100 percent passing the No. 8 sieve,
   4. 15 to 80 percent passing the No. 16 sieve,
   5. 3 to 50 percent passing the No. 30 sieve, and
   6. none passing the No. 50 sieve,

2. in a medium sand filter, well washed sand consisting of the following particle size
   1. 100 percent passing the 3/8 inch sieve,
   2. 95 percent to 100 percent passing the No. 4 sieve,
   3. 80 percent to 100 percent passing the No. 8 sieve,
   4. 45 percent to 85 percent passing the No. 16 sieve,
   5. 15 percent to 60 percent passing the No. 30 sieve,
   6. 3 percent to 15 percent passing the No. 50 sieve, and
   7. 4 percent or less passing the No. 100 sieve, or

3. alternate media that is
   1. of equivalent durability,
   2. has a particle size consistent with the size required for use in a course sand filter or medium sand filter,
   3. inert so that it will maintain its integrity and not collapse or disintegrate with time, and
   4. not be detrimental to the performance of the intermittent sand filter.

1. 100 percent passing the ½ inch sieve,
2. 18 to 100 percent passing the 1/4 inch sieve,
3. 5 to 75 percent passing the No. 4 sieve,
4. 24 percent or less passing the No. 10 sieve,
5. 2 percent or less passing the No. 16 sieve, and
6. 1 percent or less passing the No. 100 sieve.