Carbon‐nitrogen‐phosphorus removal and biofilm growth characteristics in an integrated wastewater treatment system involving a rotating biological contactor

Abstract

A new rotating biological contactor-packed media technology (RBC-PMT) is locally innovated using light polyethylene Amazon screen material as disc media. A single-stage co-current fed of this type, which is connected with a series of equalization tanks as an integrated wastewater treatment system (IWWTS), showed good carbonnitrogen-phosphorus (C-N-P) removal and unveiled biofilm growth characteristics noteworthy for treating pollutants in wastewater.The equalization tanks approached facultative anaerobic conditions while the RBC-PMT exhibited a completely aerated system, both with a slightly alkaline pH, whose temperatures are ranging from 21 to 24• C, and both performed as biological nutrient removal systems. The combined nutrient removal efficiency at high organic loading rate (HOLR) and low organic loading rate (LOLR) showed fair chemical oxygen demand (COD) removal at 65.68 and 67.89%, respectively. Nitrate-nitrogen removal demonstrated good removal at 79.17% at HOLR and 83.43% at LOLR. There was excellent phosphate-phosphorus removal determined at 91.64 and 94.35% at high and low OLRs, respectively. This indicates that increasing the organic loading rate decreases the C-N-P removal in the IWWTS.Biofilm growth was characterized by the selection and survival of microorganisms present under aerobic environmental conditions in the RBC-PMT system and their respective metabolism in removing C-N-P substrates. Yeasts, coliform bacteria particularly E. coli, Cyanobacteria, and benthic diatoms were dominant microorganisms found upon oil-immersion microscopy. Protozoans and algae including Chlorococcum, Chlorella, Diatoma, Tribonema, Oscillatoria, Euglena, and other motile rotifiers were also dominantly found in the biofilm samples. Biofilm growth is observed and its average thickness was measured to be 7.71 µm at HOLR and 2.81 µm at LOLR. Thicker biofilm at HOLR has caused the reduced rate of diffusion of the microorganisms and their metabolic products as manifested by the low C-N-P removal during HOLR. 

Effect of Wall Boundary Layer Thickness on Power Performance of a Recirculation Microbial Fuel Cell

“…Thus, the mass transfer of MFCs needed to be enhanced by increasing the Reynolds number or the flow convective [45]. Although the thickness of the biofilm would become a diffusion barrier [22] the thickness of the biofilm (about 40 µm) was smaller than the hydrodynamic boundary layer [37]. Therefore, the mass transfer of recirculation mode MFC was mainly determined by the thickness of hydrodynamic boundary layer [35,36].…”

“…Although, these studies stated that enhanced biofilm thickness lead to the enhanced electricity production of MFC, but most of the biofilm formation is dependent on natural adsorption [21]. In addition, very thick biofilms will not only block the electron transfer of MFCs [21], but also will become a diffusion barrier on the physical and chemical exchanges between the bacteria and substrate during the mass transfer processes [22].…”

Diffusion in biofilms respiring on electrodes

“…Knowledge of diffusion coefficients in biofilms is critical for measuring and predicting the chemical fluxes in biofilms and ultimately for engineering systems to manipulate bacterial biofilms for our purposes. Examples in which diffusion coefficients play a practical role include 1) penetration of antibiotics into pathogenic biofilms 2, 3 , 2) heavy metal immobilization and reduction in environmental biofilms 4, 5 , and 3) penetration of organic molecules and oxygen into biofilm reactors used in wastewater treatment 6-9 .…”

Predicting biofilm thickness and biofilm viability based on the concentration of carbon-nitrogen-phosphorus by support vector regression

“…These results further illustrate that the biofilms were the metabolic byproducts of microorganisms including bacteria and protozoans. Removal of C-N-P substrate is inhibited by biofilm thickness because of its diffusion barrier on the physical and chemical exchanges between C-N-P and the microorganisms during mass transfer above the active thickness (Cabije et al 2009). Substrate removal had a positive correlation with biofilm thickness below the active thickness (Eldyasti et al 2014).…”