Alexander Szabo and Oscar Engle - Svenskt Vatten

Method 1: Estimation of domestic water consumption
If one assumes that the average contribution of waste water per capita is 208 l/day, and the
number of people is known to be 10 500, the infiltration may be calculated (see Table 8.5).
Table 8.5: Estimation of infiltrating water, taking total water flow and assumed domestic water
consumption into consideration. **Assumes all inhabitants present. *Assumes only 1/3 of students
and staff present due to holiday.
Date
Measured total
inlet water
during 24h (m 3 )
Assumed
Domestic water
consumption (m 3 )
Infiltration (Total
– Domestic)
(m 3 )
Amount of
infiltration in
pipes
5 – 6 Nov 6346 2184** 4162 66%
18 – 19 Nov 7527 728* 6799 90%
9 – 10 Jan 5526 2184** 3342 60%
Method 2: Calculating base flow and rain peaks
The lowest flow measured during night times is considered as base flow. At this time (lowest
flow usually occurred between 04:00 a.m. and 06:00 a.m.) the water is considered to be purely
infiltrated water. The contribution from rainfall has been excluded according to Eq. 8.5 and Eq.
8.6 respectively.
Table 8.6: Calculations of infiltration by using baseflow and peak flow.
Date
Measured total
inlet water during
24h (m 3 )
Total inlet water
without base-flow
and rain peak (m 3 )
Infiltration
(Base
flow+Rainpeak)
(m 3 )
5 – 6 Nov 6346 2028 4318 68%
18 – 19 Nov 7527 1559 5968 79%
9 – 10 Jan 5526 1275 4251 77%
Amount of
infiltration in
pipes
Method 3: Calculating the COD dilution in waste water
The load per capita is assumed to be 120 g COD per day (Kemira, 2004). With assumed fresh
water consumption it is possible to estimate the theoretical concentration of COD in the waste
water.
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