Skip to content

Glossary of Terms

The following terms are commonly referred to when discussing sewage disposal:

Absorption Trench: Excavation in fill or soil, being a component of a leaching bed where a distribution pipe will be or is placed, which allows permeation of the effluent into the fill or soil.

Biomat: Naturally occurring anaerobic microorganisms that create a blackened layer along the bottom and sides of leaching bed over time.

Conventional Leaching BedA tile bed that consists of two components: a septic tank and a leaching bed.

Distribution Pipe: A sequence of perforated pipe installed in a leaching bed for the intention of distributing effluent from a septic tank or secondary treatment unit to the soil or fill in a leaching bed.

Effluent: Liquid which flows away from a containing space, such as a septic tank. Sanitary sewage that is passed through a treatment unit.

Effluent filter: An effluent filter is installed inside the septic tank and replaces what was the exit baffle. The purpose of the effluent filter is to prevent suspended solids from floating out to the leaching bed.

Filter Bed: A type of class 4 septic system that has two components: a septic tank and filter bed that requires specially mixed soil particles placed under the stone and distribution pipe.

Greywater: Wastewater from showers, laundry, and kitchen sinks, excluding toilet wastes.

Holding Tank: A tank designed for the total retention of all sewage released into it and needing intermittent discharging by a hauled sewage system.

Leaching Bed: The absorption system constructed as absorption trenches or as a filter bed, located in ground or raised above ground as required by local conditions, to which effluent from a septic tank or secondary treatment unit is applied for treatment and disposal.

Leaching: A process of draining of soluble salts, alkali and other constituents from soils or other media by natural percolation or abundant irrigation.

Portable Privy: A transportable latrine in which the receptacle for human body waste and the superstructure are connected structurally into one component.

Raw Sewage: Untreated wastewater.

Scum: Oils and greases and other material that will float forming a deposit on the top of the sewage.

Septic tank: A watertight vault in which sewage is accumulated with the intention of extracting scum, grease, and solids from the liquid without the addition of air and anaerobic digestion of the sewage being established.

Sludge: The gathered settled solids accumulated from sewage or industrial refuse, treated or raw, in tanks or basins, and comprising more or less water to build a semi-liquid accumulation.

Tertiary Treatment: Tertiary simply refers to “third” treatment. Any type of water upgrade that improves treated wastewater to meet reuse requirements. This may include general cleanup of water, or elimination or certain parts of wastes inadequately removed by conventional treatment processes. The standard process would include chemical remedies and pressure filtration. A tertiary system has a septic tank, a treatment unit and area bed. There is a mandatory annual maintenance agreement required.

Topsoil Layer: Fertile dark coloured surface soil that supports growth.

Vault Privy: A latrine in which the receptacle for the human waste consists of an assembled vault from which the refuse is intermittently extracted. This is a type of class 1 sewage system.

How Do I Perform a Field Percolation Test?

A- Test Procedure. Where a field percolation test is required, it is performed in the following manner:

  • (a) Make an excavation in the soil layer which is to be assessed for a percolation Time. It is of the following dimensions:
    • (i) between 100 and 300 mm in diameter
    • (ii) be at least 200 mm in depth below the upper level of the soil layer being assessed
  • (b) All loose material and smeared clay shall be removed from the sides and bottom of the excavation.
  • (c) Cover the bottom of the excavation with 50 mm of sand or fine gravel.
  • (d) Fill the hole with water to a depth of 300 mm (or to the surface) and determine the time it takes for the water to seep away; repeat, and if the second filling seeps away in 10 minutes or less proceed as follows:
    • (i) establish a fixed reference point, add water to a depth of 150 mm above the sand or fine gravel, and measure the water drop every 10 minutes for one hour. If for one hour the first 150 mm seeps away in 10 minutes or less, use a shorter time interval between readings.
    • (ii) refill to the 150 mm level when necessary and start another series of readings. Continue readings until the last two series of readings show a similar drop pattern (approximately equal drop in the same number of readings) or, alternatively, until the difference in the maximum and minimum drops in 3 consecutive readings is less than 5mm. In either case use the average drop of the last 3 readings in computing “T”
  • (e) If the initial fillings to 300 mm take more than 10 minutes to seep away, follow with this procedure:
    • (i) maintain at least 300 mm of water in the hole for at least 4 hours, or until the soil being tested has become swollen and saturated with water. At least 12 hours should be allowed for swelling in clay soils, although dry clay soils may require longer periods to obtain a stabilized percolation rate.
    • (ii) After swelling remove any loose material from the top of the sand or fine gravel.
    • (iii) Using a fixed reference point, adjust the water level to 150 mm above the sand or gravel and measure the water drop every 30 minutes for four hours or until a stable rate of drop is reached. If the first 150 mm seeps away in less than 30 minutes, use a 10 minute interval and run the test for one hour or until the drop rate is stabilized. A drop of 5 mm or less in a 30 minute interval is indicative of a soil of “T” close to or greater than 50 min/cm. If it is to be assessed increase the reading interval to 60 minutes.
    • (iv) Refill with water to the 150 mm level when necessary. Take readings until a stable rate of drop is reached. This may be when the drop in two successive readings does not vary by more than 1.5 mm or when the
      difference between the maximum and minimum readings of the last four readings does not exceed 5 mm. Once a stable rate is reached use the average drop of the last 3 readings in computing the percolation time.
  • (f) Percolation Time = Time Interval (minutes) divided by the Average drop of last 3 readings (cm).