Constructed wetlands are generally recognized as removal facilities for agricultural and industrial wastewater purification. Traditional constructed wetlands are developed mainly in northern Europe and USA where their need for wide surfaces can be easily met. In order to reduce such surface need, the employment of active substrates was tested in a subsurface flow constructed wetland for the treatment of wastewaters from a medium-size cheesemaking plant, located near the town of Aosta (North West Italy), in alpine environment. This wetland is a long narrow trench 1 m in depth and approximately 2 m in width, with a total surface of 200 m2, following the natural configuration and slope of the area. The trench is divided in 5 sections, filled respectively (from the beginning to the end) with gravel, ground ceramic wastes, magnetite, zeolite, local soil (added with vegetal compost and marble sand). In all the sections Phragmites australis plants are grown. Sampling pits are present in each section. The nitrogen turnover in a constructed wetland is the result of several biological activities, mainly microbial ammonification, nitrification and denitrification. The oxidation of ammonia by ammonia-oxidizing bacteria (AOB) is generally considered as critical. In our study we focussed on activity, diversity and distribution of AOB in the different sections of the alpine constructed wetland, in particular to ascertain whether different activities in different substrates are due to different communities or an influence on microbial activity is exerted by the substrates. Activity has been measured by means of a potential nitrification assay. Diversity and distribution by mean of Denaturing Gradient Gel Electrophoresis (DGGE) of 16S ribosomal DNA fragments specific to AOB. Moreover, the influence of different substrates and rhizosphere of Phragmites australis has been considered by collecting samples both in bulk and root zone; as well as the effect of temperature has been evaluated collecting samples in different seasons. First results of Potential Nitrifying Activity (PNA) analysis highlight great differences between samples, also within a same section. Zeolite seems to enhance nitrification activity. DGGE profiles revealed the presence of the same population of AOB belonging to Nitrosospira genus in all samples. Sequencing of DNA fragments will be performed in order to confirm such indication.
File in questo prodotto:
Non ci sono file associati a questo prodotto.