Simulation of Wastewater Depolution Processes by Advanced Biological Methods

Abstract

This paper presents the results from a study which simulates wastewater depollution processes using advanced biological methods. The experimental research was performed in a static biological reactor, equipped with an air compressor and an agitator / mixer. Synthetic wastewater, prepared with the addition of glucose, was fed into the reactor. The wastewater was subjected to alternating cycles of aeration and slow mixing, for consecutive 3 h intervals within the reactor to ensure the necessary conditions for the reduction of nitrogen based organic compounds within the wastewater. In the successive aeration processes, aerobic / nitrifying microorganisms which developed within the reactor, facilitated the decomposition of organic substances into nitrites and then into nitrates. By stopping aeration and starting the slow mixing cycle the anaerobic / denitrifying microorganisms growing in the reactor consume the necessary oxygen from nitrates and release free nitrogen into the atmosphere, thus completing the process of advanced depollution. Therefore, the experimental procedure highlights the existence of two distinct phases in the development of the depollution process. In the first phase, the biological process is initiated using glucose in order to promote the growth of the bacterial flora. In the second phase (the regime phase), the reduction of mineral and organic pollutants from the wastewater is ensured. The activity of microorganisms in the biological reactor can be further supported by the recirculation of activated sludge retained in the secondary decanter. The proposed technology offers a fast, safe and relatively inexpensive method for advanced wastewater depollution. Bioreactors of this type are recommended in wastewater treatment schemes in the hearth of rural localities, agro-zootechnical complexes and tourist units with seasonal activities due to their fluctuations in hourly wastewater flow rates. Similar approaches can also be considered for the elimination of ammonium compounds in groundwater polluted with animal manure.

Saving Energy in Biological Wastewater Treatment by Using Extremely Low-Frequency Electric Field—Pilot-Scale Study

“…This implies the use of active sludge microorganisms [38,40,48,49] such as aerobic and anaerobic bacteria, microalgae, and molds [50,51]. These microorganisms metabolize the organic pollutants from the wastewater processed in the mechanical and chemical stages, including those containing nitrogen and phosphorus [52]. Since these processes are relatively slow, biochemical treatment takes a long time.…”

“…Therefore, the consumption of energy during the biochemical purification stages is relatively high and is due to the operation of the recirculation pumps, of the air compressors for oxygenation, of the mechanical agitators, etc. As reported in the literature, the energy consumption associated with the biochemical treatment stages usually represents more than 60% of a wastewater treatment plant's total energy consumption [45,47,48,52]. As reported in [48,50,53], bioactivators can be used to increase the metabolism rate and thus to diminish the biochemical treatment time.…”

Electromagnetic Stimulation of Microbial Activity in Wastewater Treatment: Experimental Equipment

“…The aerobic and anaerobic steps can be performed in successive bioreactors (continuous flow) or the same bioreactor (batch flow), sequentially oxygenated by bubbling with air (aerobic processing) or homogenized with a mixer (anaerobic processing) [38].…”