Wastewater Characteristics

Wastewater Characteristics involved in Percolation Application

For the purposes of this CoP, a single-house system refers to a system serving a dwelling house of up to 10 people with toilet, living, sleeping, bathing, cooking and eating facilities.

The strength of the inflow in terms of biochemical oxygen demand (BOD) into an on- site system will largely depend on the water usage in the house; for example, houses with dishwashers may have a wastewater BOD strength reduced by up to 35% due to dilution even though the total BOD load to the treatment system (kg/day) remains the same. Household garbage grinders/sink macerators can increase the BOD loading rate by up to 30% and their use is not recommended for dwellings, as they result in additional maintenance requirements due to increased solids, increase in electricity usage and do not encourage recycling, i.e. composting of organic wastes (Carey et al., 2008). The treatment systems covered by this CoP are not appropriate for the disposal of excessive quantities of waste oil and fats. These waste materials should be collected and disposed of by another appropriate method.

TABLE 4.1. RANGE OF RA W CHARACTERISTICS (I.S. EN 12566-3:2005).

Under no circumstances should rainwater, surface water or run-off from paved areas be discharged to on-site single-house treatment systems. However, grey waters (washing machine, baths, showers, etc.) must pass to the treatment system. To control the quantity of wastewater generated in a household, water conservation measures should be adopted.

Table 4.1 gives the range of influent characteristics for raw domestic wastewater from I.S. EN 12566-3:2005. The CEN standard requires that wastewater treatment systems must be tested using influents in this range. Research in Ireland indicates that Irish domestic wastewater is at the more concentrated level of the characterised influent in I.S. EN 12566-3:2005, which in turn produces a typically concentrated effluent (see Table B.1 in Annex B).

The total design wastewater load should be established from the maximum population that can inhabit the premises, based on number and size of bedrooms. In order to calculate wastewater capacities, a typical daily hydraulic loading of 150 l/person should be used to ensure that adequate treatment is provided.