Removal of ammonia peaks from effluent wastewater using nitrifying biolm on zeolite

Abstract

Elevated levels of ammonia in discharged water leads to eutrophication and potential toxicity in water bodies. To combat nitrogen pollution, strict ammonium discharge limits of 1 mgNH₄-N/L standard is set by the water framework directory. In many cases, current wastewater treatment facilities struggle to consistently meet this standard, particularly during peak concentration periods. For years now, the influent's peak pattern has been mirrored in the biologically treated water and currently, there lacks an effective solution to address this issue. This study explores use of zeolite in a biological filter, a potential technology to remove ammonia peaks from effluent wastewater. The fundamental concept of this technology involves combining zeolite with a nitrifying biofilm. In this process, the zeolite dampens the ammonia peak by adsorption, while the nitrifying biofilm regenerates the zeolite. Clinoptilolite, a natural zeolite of 1mm particle size and synthetic wastewater were chosen in this study. The impact of competing cations was investigated due to clinoptilolite's affinity for cations. It was found that the presence of other cations decreases ammonium removal capacity by 6.2 times of which potassium is the main competitor. But, percentage of potassium removed is much less than ammonium though it's concentration is 5 times higher. 44.2% of the total potassium was removed in 60 minutes compared to 70.9% ammonium removal. In the experiments with the nitrifying biofilm, it was found, that it does
not affect rate of adsorption by zeolite, but enhances ammonium removal. Experimental results indicate that zeolite can be bio-regenerated effectively, and rate of conversion is faster than rate of desorption of adsorbed ammonium. The system of zeolite and biofilm has some buffer capacity, but cannot compensate for the bicarbonate anions needed for H⁺ released. A BioWin model
was designed to simulate the survival of biomass during extended periods of low concentration, and the results indicated that conversion capacity of the system reduces after 7 days of DWF concentrations. But the biomass can sustain longer periods of DWF concentrations, but it takes some time and exposure to higher substrate concentrations to revive it's capacity. In conclusion this study
confirms the potential in this technology and confirms effective bio-regeneration capabilities. The results from this research can built upon to answer questions regarding knowledge gaps with reactor operation and design. This paves the way for future studies to make it an industrially viable technology.