Zeolite as a Potential Medium for Ammonium Recovery and Second Cheese Whey Treatment

Abstract

The efficiency of natural zeolite to remove ammonium from artificial wastewater (ammonium aqueous solutions) and to treat second cheese whey was examined, aiming to recover nitrogen nutrients that can be used for further applications, such as slow-release fertilizers. Sorption experiments were performed using artificial wastewater and zeolite of different granulometries (i.e., 0.71-1.0, 1.8-2.0, 2.0-2.8, 2.8-4.0, and 4.0-5.0 mm). The granulometry of the zeolite had no significant effect on its ability to absorb ammonium. Nevertheless, smaller particles (0.71-1.0 mm) exhibited quicker NH 4 + -N adsorption rates of up to 93.0% in the first 10 min. Maximum ammonium removal efficiency by the zeolite was achieved at ammonium concentrations ranging from 10 to 80 mg/L. Kinetic experiments revealed that chemisorption is the mechanism behind the adsorption process of ammonium on zeolite, while the Freundlich isotherm model fitted the experimental data well. Column sorption experiments under batch operating mode were performed using artificial wastewater and second cheese whey. Column experiments with artificial wastewater showed high NH 4 + -N removal rates (over 96% in the first 120 min) for all granulometries and initial NH 4 + -N concentrations tested (200 and 5000 mg/L). Column experiments with second cheese whey revealed that natural zeolite can remove significant organic loads (up to 40%, 14.53 mg COD/g of zeolite) and NH 4 + -N (about 99%). For PO 4 3− -P, the zeolite appeared to saturate after day 1 of the experiments at a removal capacity of 0.15 mg P/g of zeolite. Desorption experiments with water resulted in low NH 4 + -N and PO 4 3− -P desorption rates indicating that the zeolite could be used as a substrate for slow nitrogen release in soils.

Second Cheese Whey Treatment Using Zeolite under Continuous Flow Mode and Its Application on Wheat Growth

“…The second cheese whey (SCW) used in this study was obtained from the Papathanasiou S.A. dairy (Agrinio, Greece), transported to the laboratory in plastic bottles, and then stored at −20 • C until use to prevent any change in its composition. The COD concentration of the undiluted SCW was 28.500 mg/L, total Kjeldahl nitrogen (TKN) was 243 mg/L, NH 4 + was 45.27 mg/L, PO 4 3− was 196.69 mg/L, and its pH was 4.2 [15].…”

“…The natural zeolite used in the experiments, originated from Bulgaria (Imerys Minerals Bulgaria AD, imported by Zeolife TM Company, Nea Orestiada, Greece), and is a hydrated aluminosilicate mineral of volcanic origin (clinoptilolite content: 85%; moisture content: 10-12%; impurities of feldspar, micas, and clays free of fibers and quartz: 3-5%). According to the technical data sheet provided, the minimum cation exchange capacity value of this specific zeolite is 150 meq/100 g. Prior to all experiments, the zeolite was sieved to obtain the desired granulometry (i.e., 2.0-2.8 mm), washed to remove dust, and finally dried [15].…”

“…Zeolite of granulometry 2.0-2.8 mm was used for the continuous flow column experiments to determine the zeolite's maximum adsorption capacity for ammonium. This specific granulometry was chosen based on previous experiments examining the efficiency of zeolite to remove ammonium from SCW and AWW under batch operating conditions [15]. The columns used for the experimental setup are described in Kotoulas et al [15] and comprised Plexiglas tubes, 40.0 cm in height with a 4.0 cm internal diameter, equipped with four sampling valves placed at different heights ( Figure 1).…”

“…This specific granulometry was chosen based on previous experiments examining the efficiency of zeolite to remove ammonium from SCW and AWW under batch operating conditions [15]. The columns used for the experimental setup are described in Kotoulas et al [15] and comprised Plexiglas tubes, 40.0 cm in height with a 4.0 cm internal diameter, equipped with four sampling valves placed at different heights ( Figure 1). Each column was filled with 500 g of 2.0-2.8 mm zeolite.…”

“…On the other hand, circular economy principles express that wastewater treatment should be combined with simultaneous energy production and/or nutrient recovery. For this purpose, various zeolites (natural or modified) have been tested as low-cost absorbents to adsorb nutrients (i.e., nitrogen and phosphorus) from agro-industrial wastewater streams [9][10][11][12][13][14][15]. It should be mentioned that most previous research has examined the use of zeolite under batch mode and continuous flow experiments are limited [12,[16][17][18][19].…”