MSc Students Presentations - Angelos Kotoulas

Recently, the increase in the world's population has been accompanied by the need to meet its nutritional requirements. This fact contributes to an increase in the productive process of agro-industrial units in order to be achieved adequate food supply to this population. However, its’ consequence is the production of an increased volume of liquid waste, which needs to be managed directly due to the enormous environmental impact created by its thoughtless disposal to natural “recipients”.

Based on the aforementioned, an economical method of agro-industrial wastewater treatment, namely of cheese whey, is being studied in the present postgraduate thesis. In particular, natural zeolite of Bulgarian origin is used, which is an inexpensive sorbent material in order to be examined not only the nitrogen adsorption capacity in the form of ammonium nitrogen (N-NH₄⁺) from liquid waste streams, but also the possibility of recovering it.

In this context, preliminary experiments of kinetic ammonium adsorption in natural zeolite from artificial wastewater were carried out in bottles. Then, whey waste adsorption experiments were performed using laboratory scale columns filled with zeolite in batch mode. Various operating parameters such as the effect of initial cheese whey concentration, the effect of temperature, the duration of adsorption capacity, as well as the efficiency of adsorption using various sizes of zeolite were examined in these columns. The final stage of the study included a greenhouse pot experiment in the period from December 2017 to March 2018. Wheat plants (Triticum spp) were used as an experimental plant. The main goal of this experiment was the examination of the possibility of recovering ammonium nitrogen from saturated zeolite in wheat plants.

Preliminary experiments with artificial wastewater revealed that the difference in granulometry of zeolite does not affect the adsorption capacity, in contrast with the initial concentration that influences it significantly, as an increase in the initial concentration leads to an increase in adsorption capacity. In the case of real cheese whey wastewater columns experiments, removal of organic matter expressed as COD as well as orthophosphate removal (P-PO₄^3-) was also examined. It was observed that the ammonium ion adsorption capacity was high, since a completely removal is achieved from cheese whey even for more than one day of columns’ operation with the same zeolite. Regarding the organic matter adsorption, approximately 20-35% removal was observed, while the maximum othophosphates removal was up to 76% for the first day of operation.

Finally, based on the results obtained from the ammonium nitrogen recovery experiments, a saturated amount of zeolite was applied to different treatments in pots of wheat seeds, which were allowed to grow with the absence of additional chemical fertilizer. The results showed, according to the statistical analysis occurred, that the zeolites contributed significantly to the plants’ growth as pots containing zeolite showed a statistically significant difference in terms of the size of grains’ dry mass. Therefore, the addition of such zeolite to different crops may be promising and could partially replace the use of chemical fertilizers, which are responsible for the pollution of ground water and surface water with inorganic pollutants, such as nitrates