Recharge systems for protecting and enhancing groundwate

TOPIC 4
Pathogens and micro pollutants / Health aspects 495
Mcyst concentration [g/l] at outlet
2.5
2
1.5
1
0.5
measured
modelled
1
0
0 5 10 15 20 25 30
0
Time t [h]
Figure 3. Measured and modelled MCYST-concentrations in 20 cm depth
during enclosure experiment E2 (diamonds: MCYST-concentration in the inlet);
parameters for the given situation are: ν = 0.32 m/h, α L = 0.0063 m, R = 1.97, λ = 0.74 l/h
Table 2. Retardation coefficients and degradation rates calculated for extracellular MCYST
during two enclosure experiments E2 and E3
retardation coefficient
(R)
6
5
4
3
2
Mcyst concentration [g/l] at inlet
degradation rate (λ)
[1/d]
Experiment
E2 E3 E2 E3
water reservoir -> 20 cm 1.97 1.76 17.8 13.0
20 cm -> 40 cm 1.9 1.25 5.76 7.44
40 cm -> 60 cm 1.0 1.36 18 4.56
60 cm -> 80 cm 1.0 1.14 13.0 0.24
80 cm -> outlet 1.58 1.3 1.68 1.68
In order to compare adsorption parameters obtained from laboratory batch experiments to those calculated on the
basis of field enclosure experiments k d -values were calculated on the basis of the retardation coefficients according
to (1), with n e ranging from 0.16 to 0.4 and ρ s amounting to an average of 1.65 g/cm³.
k
d
⎛ ne
⎞
= ⎜ ⎟ * R − 1
⎝ ρ ⎠
s
( )
Eqn. (1)
The resulting average k d -value for experiments E2 and E3 amounted to 0,14 cm 3 /g and 0.07 cm 3 /g, respectively.
This is less than 50% of the values obtained in the batch experiments. This might be due to the different ratio of
water to sediment (batch experiment 1:1, enclosure experiment about 3:1).
10 – 16 June 2005, Berlin ■ 5th International Symposium ■ AQUIFER RECHARGE ■ ISMAR 2005