Specialist Group on Use of Macrophytes in Water Pollution ... - IWA

ammonium concentration in the outlet (Kadlec and Knight 1996). On the other hand,
ammonia-nitrogen can be reduced by several processes, which include adsorption, plant
uptake and volatilization. However, it is generally believed that the contribution of these
processes is very limited (Lee et al. 2009).
Experimental results also indicate that the wetland sediments were saturated with MRP,
therefore, acting as a source for MRP (Figure 4 and 5). The alteration of environmental
conditions triggered the phosphorus releasing process, resulting in a decrease of the removal
efficiency. Moreover, the phosphate-accumulating microorganisms were sensitive to high
salinity (Scholz 2006). The high chloride concentration possibly supported the release of
phosphorus from the mature sediments.
Concentration (mg/l)
160
140
120
100
80
60
40
20
0
COD Ammonia-N MRP
Variables
Influent
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20 IWA <strong>Specialist</strong> <strong>Group</strong> on Use of Macrophytes in Water Pollution Control: Newsletter No. 37
Tap I
Tap II
Tap III
Figure 4. Water quality variables for farmyard runoff mesocosms. (Tap I: surface flow water;
Tap II: oxidized sediment layer; Tap III: reduced sediment layer; COD: chemical oxygen
demand; Ammonia-N: ammonia-nitrogen; MRP: molybdate reactive phosphorus).