The impact of precipitation and external carbon source addition on biological nutrient removal in activated sludge systems – experimental investigation and mathematical modeling

Abstract

The aim of this study was to determine the effects of chemical precipitation and addition of external carbon sources on the denitrification capability and enhanced biological phosphorus removal (EBPR) interactions at the ‘Wschod’ WWTP (600,000 PE) in Gdansk (northern Poland). For this purpose, different kinds of batch experiments were carried out with the settled wastewater (without pretreatment and after coagulation-flocculation) and external carbon sources (ethanol and fusel oil). Precipitation of colloidal and particulate organic fractions has a significant effect on denitrification and EBPR. The removal of these two fractions by coagulation-flocculation resulted in the reduced process rates (30–70%). The experimental investigations were supported by both lab-scale and full-scale simulations using a newly developed model as an expansion of the Activated Sludge Model No. 2d (ASM2d). The new model accurately predicted the effects of precipitation and external carbon addition in batch experiments. Full-scale simulations revealed that addition of external carbon source can compensate the effects of precipitation resulting in a similar NO3-N behavior compared to the reference case (without precipitation and external carbon addition). The combined effects of precipitation and addition of external carbon source resulted in a significantly different PO4-P behavior compared to the reference case.

The Influence of COD Fraction Forms and Molecules Size on Hydrolysis Process Developed by Comparative OUR Studies in Activated Sludge Modelling

“…This approach drew on the concept, suggested Maruéjouls et al [47], that PSVD is a determining factor for the prediction of the wastewater quality along a catchment, a combined sewer, or a primary treatment system. This research, as well as studies conducted by other authors [47,[51][52][53][54][55]57], confirms that a comparative study of the original and modified ASM2d models that accounts the effects of the COD fraction and particles sizes of molecules on the hydrolysis process should be applied under transient conditions (summer, spring and winter). The distribution data were fed into the hydrolysis model that involved a comparison of results on the wastewater quality that were obtained in the course of simulations that were performed at the hydrolysis rates of particles (such as molecules size and forms of COD substrates) that depended on the OUR batch tests as well as the conditions of the settling velocities ( Figure 5).…”

“…The goal of the presented research was to show the potential of these particulate forms of COD in order to better describe the hydrolysis that occurs in the course of the wastewater treatment bioprocesses (e.g., pre-denitrification and denitrification-nitrification) in an activated sludge system and to better predict the quality of the WWTP effluent. This paper compared the calibration and validation of the original and modified ASM2d models by using experimental data that were obtained by conducting respirometric OUR tests on wastewater samples that were fractionated by different sizes of COD molecules and their forms, as well as from studies conducted by the authors [26,[51][52][53][54][55]. For example, the experiments that were performed in [56] showed that when wastewater flows from an urban catchment to the biological treatment, the particle settling velocity distribution (PSVD) becomes highly differentiated.…”

A modified BAF system configuring synergistic denitrification and chemical phosphorus precipitation: Examination on pollutants removal and clogging development

“…Though the enhanced chemical pre-treatment step can reduce total phosphorus in the BAF influent, removal of considerable amount of organic matters would also be resulted meanwhile (Rogalla et al, 1990). The simultaneous organic matter removal in the chemical pre-treatment step may lead to shortage of carbon sources in the subsequent biological nitrogen removal process and hence result in reduced denitrification efficiency (Makinia et al, 2012), particularly when treating weak domestic wastewater with relatively low C/N ratio. For compensating the loss of carbon source, the addition of external carbon sources in the denitrification process are often required, and therefore operation cost increases.…”

Model based evaluation of plant improvement at a large wastewater treatment plant (WWTP)

“…[1] In these circumstances, effective use of biodegradable substrates as an internal carbon sources for denitrification and enhanced biological phosphorus removal as well as optimizing the performance of aeration systems in bioreactors, may be useful for saving energy at WWTPs. [2][3][4] In this situation, the aeration control in the bioreactors is very important, because it is one of the most energy-consuming processes in the wastewater treatment. [5] The energy consumption in the aeration systems usually ranged 50% to 90% of the total electricity consumed by the WWTP (depending on size and technological solutions of plant), which corresponds to 15-40% of the total costs in the wastewater treatment budget.…”