Influence of ORP variation, carbon source and nitrate concentration on denitrifying phosphorus removal by DPB sludge from dephanox process

Abstract

The effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by denitrifying phosphorus removal bacteria sludge was systematically studied using batch experiments, at the same time the variation of ORP was investigated. Results showed that the denitrifying and phosphorus uptake rate in the anoxic phase increased with the high initial anaerobic carbon source addition. However, once the initial COD concentration reached a certain level, which was in excess of the PHB saturation of Poly-p bacteria, residual COD carried over to the anoxic phase inhibited the subsequent denitrifying phosphorus uptake. This was equal to supplementing the external carbon source to the anoxic phase, furthermore the higher the external carbon source concentration the more powerful the inhibition caused. High nitrate concentration in the anoxic phase increased the initial denitrifying phosphorus rate. Oncethe nitrate was exhausted, phosphate uptake changed to phosphate release. Moreover, the time of this turning point occurred later with the higher nitrate addition. On the other hand, through on-line monitoring the variation of the ORP with different initial COD concentration, it was found that ORP could be used as a control parameter for phosphorus release, but it is impossible to utilize ORP for controlling the dinitrification and anoxic phosphorus uptake operations.

A Modified Bio-Ecological Process for Rural Wastewater Treatment

“…This ratio determines the carbon source and nitrate quantity in the anoxic tank, and both these parameters can affect the denitrification process [40]. Therefore, the reflux ratio is one of Organic loading rate (OLR) is a chief factor that indicates the amount of volatile solids to be fed into the reactor every day [37].…”

“…This ratio determines the carbon source and nitrate quantity in the anoxic tank, and both these parameters can affect the denitrification process [40]. Therefore, the reflux ratio is one of the most significant parameters affecting the treatment efficiency.…”

Progress in the Development of Control Strategies for the SBR Process

“…ORP control strategy has been applied in activated sludge processes (include the SBR process) since the 1980s [39,51,52]. A recent study conducted lab-scale SBR batch experiments to evaluate denitrifying phosphorus bacteria sludge (DPBS) and found that ORP curves provided a good indication of the phosphate release endpoint during the anaerobic phase, but showed poor performance when used to control the anoxic phase and aerobic phase [53]. Accordingly, if this control strategy was applied to the SBR process it would be severely limited.…”

Denitrifying phosphorus removal with nitrite by a real‐time step feed sequencing batch reactor

“…ORP could be used for process control of phosphorus removal in the A 2 SBR process. 1 However, Wang et al 11 reported that ORP itself could not be used for the judgment of phosphorus uptake. They ascribed this to the change of the metabolism pattern.…”

“…8 -10 Although the variation of ORP has been used as a tool to determine the end of phosphorus release, it cannot be used to control denitrification and anoxic phosphorus uptake by denitrifying phosphorus removal bacteria (DPB) sludge taken from the dephanox process. 11 Titrimetry has been used to monitor anaerobic-anoxic enhanced biological phosphorus removal (EBPR) on line. However, the method was comparatively complicated.…”