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Vertical flow constructed wetlands for the treatment of inorganic ...

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• Characterize <strong>the</strong> AOB community in a full scale VF wetland subject to<br />

metal accumulation.<br />

The objectives above were addressed by conducting three major laboratory<br />

experiments and by having a full scale industrial wastewater <strong>treatment</strong> train,<br />

composed <strong>of</strong> wetland <strong>of</strong> various ages, as a case study. The experiments and case<br />

studies are elaborated in <strong>the</strong> chapters following <strong>the</strong> Literature Review (Chapter 2) as<br />

explained below.<br />

Chapter 3 examines <strong>the</strong> hydraulic loading limits in terms <strong>of</strong> ammonia oxidation<br />

in intermittently fed VF <strong>wetlands</strong> operating at different salinities and attempts to<br />

characterise <strong>the</strong> AOB in <strong>the</strong>se systems in relation to NaCl concentration, depth and<br />

season.<br />

Because <strong>of</strong> <strong>the</strong> aerobic conditions prevailing in unsaturated VF <strong>wetlands</strong> <strong>the</strong>se<br />

systems are very efficient in nitrifying but fail to denitrify and <strong>the</strong>re<strong>for</strong>e present low or<br />

absent nitrate or total nitrogen removal capacity. A modification <strong>of</strong> <strong>the</strong> systems used<br />

in Chapter 3 is investigated in Chapter 4. These batch fed VF <strong>wetlands</strong> are unsaturated<br />

in <strong>the</strong> main filtering layer and are kept constantly saturated in <strong>the</strong> drainage layer where<br />

acetic acid is introduced as source <strong>of</strong> reducing power <strong>for</strong> denitrification. Nitrifying and<br />

denitrifying per<strong>for</strong>mance in saline and non saline conditions are examined and <strong>the</strong><br />

respective bacterial groups characterised.<br />

The suitability <strong>of</strong> using low cost organic carbon sources <strong>for</strong> denitrification is<br />

discussed in Chapter 5. External carbon sources such as methanol, ethanol, molasses or<br />

acetic acid can represent an extra cost in nitrogen removal systems; in this chapter high<br />

COD wastewater from a s<strong>of</strong>t drink manufacturing plant was tested as a carbon source<br />

in saturated VF <strong>wetlands</strong>.<br />

The per<strong>for</strong>mance <strong>of</strong> a large scale <strong>constructed</strong> wetland treating <strong>inorganic</strong><br />

wastewater at CSBP is analysed in Chapter 6. A focus on how heavy metals distribute in<br />

<strong>the</strong> sediment and plant rhizome is given in this chapter. Chapter 7 describes nitrogen<br />

removal and <strong>the</strong> associated AOB in this system.<br />

6

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