The type of septic system required for your project can vary depending on the usage details of the facility to be serviced, on-site soil and groundwater conditions, the available area for a septic field, etc. Septic systems in BC servicing under 5000 Igpd are generally divided into three categories as follows:

Type 1 systems are defined as any on-site septic system using a septic tank as the primary means of sewage treatment. Septic tanks are equipped with screened effluent filters and high-level alarms, and Type 1 disposal fields can consist of subsurface trenches, at-grade seepage beds, or above-grade sand mounds. Type 1 disposal fields can sometimes be gravity fed, but pressurization is recommended to increase system reliability and services life. Pressurization of the disposal field may be required as per current guidelines and regulations.

Type 2 systems are defined as any septic system using a Type 2 treatment plant as the primary means of sewage treatment. Type 2 treatment plants are required to produce effluent quality that meets or exceeds the following standards:

1. 5-day Biochemical Oxygen Demand (BOD5) ≤ 45 mg/L

2. Total Suspended Solids (TSS) ≤ 45 mg/L

Type 2 treatment plants usually employ aerobic treatment processes (i.e. adding oxygen) to treat domestic sewage, using an integrated air blower to mix oxygen with the sewage. As with Type 1 systems, Type 2 disposal fields can consist of trenches, seepage beds, or sand mounds. Type 2 disposal fields are typically smaller than Type 1 fields, and can sometimes be gravity fed. However, pressurization is recommended to increase system reliability and service life. Pressurization of the disposal field may be required under the current regulations.

Type 3 systems are defined as any septic system using a Type 3 treatment plant and a disinfection unit as the primary means of sewage treatment. Type 3 treatment systems are required to produce effluent quality that meets or exceeds the following standards:

1. 5-day Biochemical Oxygen Demand (BOD5) ≤ 10 mg/L

2. Total Suspended Solids (TSS) ≤ 10 mg/L

3. Fecal Coliform (FC) ≤ 400 CFU/100ml

This effluent is of a very high quality, and a properly functioning Type 3 treatment plant produces very clear, odourless effluent. Type 3 treatment plants usually employ aerobic treatment processes (i.e. adding oxygen) to treat domestic sewage, using an integrated air blower to mix oxygen with the sewage. However, different methods can be used to achieve this effluent quality. Disinfection is achieved using chlorination/de-chlorination, ozone, or ultraviolet (UV) light. UV systems are most common due to low capital cost and ease of maintenance. The vast majority of Type 3 disposal fields are pressurized, and can consist of subsurface trenches, seepage beds, or sand mounds. Type 3 disposal fields are typically smaller than Type 1 or Type 2 fields.

In some cases Type 3 systems are used even when Type 1 or Type 2 system conditions exist on the subject property. This is usually done when the space available for the disposal field is small, and a large reduction in field size is needed. A Professional Engineer is required to oversee any Type 3 septic project in BC. Some jurisdictions also require removal of nutrients such as nitrogen and phosphorus from the effluent prior to effluent discharge. This removal can be achieved using different technologies.