Recharge systems for protecting and enhancing groundwate

TOPIC 6
Region issues and artificial recharge case studies / Case studies 695
Stage 1: continuous operation, filtration rate 2.2 m/d
Stage 2: intermittent operation, filtration rate 2.2 m/d
Stage 3: intermittent operation, filtration rate 3.8 m/d
Stage 4: continuous operation, filtration rate 1.0 m/d
Samples of influent and effluent of the filter columns and the
pilot scale field filter basins were collected and analysed for
temperature, conductivity, oxygen, oxygen reduction potential,
turbidity, SAK 254 , pH, metals (iron, manganese, copper,
nickel, zinc), DOC, TOC, nitrate, nitrite, ammonium and sulfate.
Sampling procedures and determination of chemical
parameters were accomplished according to German standard
methods (Drinking Water Ordinance, 2001). Microbiological
parameters were analysed in another subproject of the central
research project.
Figure 1. Filter columns
in an air-conditioned room
RESULTS AND DISCUSSION
The results of the experiments showed differences in the purification efficiency of the investigated filter materials
depending on temperature and parameter. In Table 2 the mean concentrations of DOC and ammonium in the
influent of the test plants are listed. With increasing temperatures the DOC and ammonium concentrations were
reduced to avoid anaerobic filter conditions. Figure 3 illustrates the relative DOC and ammonium concentrations in
the columns effluents (Coconut fibres were not investigated at the temperature 5- 10°C).
Table 2. Mean concentrations of DOC and ammonium in the influent of the test plants
Influent (= spiked surface water)
Test plant and temperature
Column tests
Pilot scale field tests
DOC [mg/L]
Ammonium [mg/L]
5–10°C 7 mg/l 5.2 mg/l
20°C mg/l 2.9 mg/l
30 °C 5 mg/l 1.9 mg/l
30°C 5 mg/l 1.4 mg/l
Concerning the reduction of DOC a comparable development of the relative concentrations was detected for the
different filter materials (Figure 3, left part). The range of the C/C 0 – ratio grew with increasing temperatures.
Recycled crushed glass and sand showed rather similar results whereas the coconut fibres were characterised by an
organic emission (predominantly humates) increasing with higher temperatures. This effect became even more
intense in den start-up stages of the tests. The main part of this organic emission of the coconut fibres consisted of
humic substances.
The degradation of ammonium was similar for all tested filter materials (Figure 3, right part). The results proved
the strong dependence of this process on the temperature. An optimum for nitrification is given at a temperature
between 28 and 36°C. Below 12°C this process slows down and below 8°C it nearly stops. The pH value of the
effluents ranged from 7 to 8 which is also an optimum for nitrification. The development of the concentrations of
nitrate and nitrite on the other hand was different for the tested filter materials. A significant accumulation of nitrite
10 – 16 June 2005, Berlin ■ 5th International Symposium ■ AQUIFER RECHARGE ■ ISMAR 2005