| Horizontal subsurface flow wetland was deeply studied on adsorption properties ofthe media, selection of plants and the purifying effect of the pilot plant by lab test andpilot test on site, complying with the drainage situation of municipal wastewatertreatment plant and water quality requirements of urban landscape waters.Static adsorption experiment showed that zeolite and slag have good adsorptioncapacity of nitrogen and phosphorus. The ammonia nitrogen adsorption isotherms ofzeolite conformed to the Langmuir equation, with the maximum adsorption capacity of430g/kg when the particle size of1-2mm and the temperature of20℃. Slag tended tohave good adsorption of phosphorus, which conformed to the Freundilich equation.Meanwhile, the Ca+, Mg2+and Al3+dissolved out of the slag was able to formprecipitates with phosphorus in water.Three construted wetlands were built on the pilot site, choosing three kinds ofmedias (zeolite, slag, and gravel) and four plants (reed, cattail, canna and irispseudacorus) with different filling ratios, sequences and cropping patterns. During thestudy period, the removal rate of COD, TN, TP and NH3-N were47.07%,36.36%,72.15%and73.68%, respectively. The paper discussed the winter insulation measuresand operating results in wetland. The effluent water qualities of reed insulation werebetter than none which temperature is3℃higher. The removal rate of COD, TN, TPand NH3-N were respectively20.74%,19.36%,42%and32%with the reed bedinsulation.In response to the decreasing temperature, the activity of denitrifying bacteria wasinhibited in autumn and winter, therefore it was necessary to add suitablecarbon/nitrogen ratio (C/N) of methanol to wetlands in order to strengthendenitrification. The effluent achieved “urban wastewater reclamation and reuse waterfor landscape and environmental water quality”(GB/T18921-2002) standard withTN<15mg/L when C/N=1.85. |
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