Sharif Digital Repository

A laboratory scale study using a modified rotating biological contactor (RBC) was constructed to assess aerobic treatment of toluene, a typical aromatic hydrocarbon. The RBC consisted of 72 parallel discs rotating in a reservoir and was arranged in three stages, i.e. 24 discs oriented in each stage. An artificial wastewater containing toluene was fed to the RBC, inoculated with an enriched culture from petrochemical sewage. The rotation of the discs and the recycling time ensured good mixing of the bulk liquid and resulted in a regular biofilm thickness. Toluene removal was measured by COD measurement and GC. The effect of initial toluene concentration on toluene biodegradation showed a zero... 

Biodegradable chitosan nanoparticles (CSNPs) with an intrinsic antimicrobial activity may be a good choice to improve the effectiveness of antimicrobial photodynamic inactivation (APDI). The aim of this study was to investigate the effect of CSNPs on the efficiency of methylene blue (MB)-mediated APDI of Staphylococcus aureus and Pseudomonas aeruginosa biofilms. We also assessed the phototoxicity of MB + CSNPs towards human fibroblasts. Methods: CSNPs were prepared using ionic gelation method and characterized by dynamic light scattering (DLS) and field-emission scanning electron microscope (FESEM). Biofilms were developed in a 96-well polystyrene plate for 24 h. In vitro phototoxic effect... 

A simple biofilm model based on a model suggested by Soda et al. [S. Soda, E. Heinzle, M. Fujita, Modeling and simulation of competition between two microorganisms for a single inhibitory substrate in a biofilm reactor, Biotechnol. Bioeng. 66 (1999) 258-264] was used to simulate the competition between two microorganisms for space and a single inhibitory substrate in a biofilm reactor. Different growth kinetics were used to describe the growth of two microorganisms A and B which utilize the inhibitory substrate and the effect of biofilm thickness on microorganism concentration in biofilm was discussed. It was assumed that the biofilm has a uniform thickness and is composed of N segments (N =... 

The correct quantification of porosity is essential in all studies pertaining to porous media. A host of existing works employs a constant, bulk value for porosity, even when the porous sample is attached to a free fluid. Since the volume fraction of the solid matrix near the interface region differs from that in the core, the porosity undergoes a spatial variation. Here we present a novel relation for the porosity as a function of depth below the interface, using the concept of surface roughness applied on the classical definition of open porosity. This relation has been verified by computational modeling as well as non-invasive laser experiments. It has been shown that this depth-dependent... 

Nutrient pollution has become a global environmental issue. Innovative biological nutrient removal (BNR) processes are needed to overcome the drawbacks of conventional technologies. This study evaluates the potential of a hybrid 5-stage Bardenpho - moving bed biofilm reactor (MBBR) process for organic carbon and nutrient removal from municipal wastewater at different hydraulic retention time (HRT) and nitrate recycle ratio (R). Response surface methodology (RSM) based on a central composite design (CCD) of thirteen experiments was applied to optimize the nitrogen and phosphorus conversion of the treatment system. High removal efficiencies of about 98.20%, 92.54%, 94.70% and 96.50% for total... 

Biofiltration of Triethylamine (TEA) vapor used as a catalyst in casting operations was evaluated in this study The unit consisted of a 6-L three-stage biofilter containing a mixture of compost and wood chips (40:60 v/v) as the filter medium. Seed microbial population from municipal activated sludge was acclimated for a period of three weeks prior to the actual experimental runs. In the startup period, high pH values up to 10 was observed due to alkaline nature of TEA and inadequate formation of biofilm and low overall biodegradation. Steady increase of organic-N concentration along with gradual upward trend of pressure drop indicated sound establishment of microbial population. Operational... 

Experiments were conducted to investigate the behaviour of moving bed biofilm reactor (MBBR) receiving a mixture of toxic (phenolic) wastewater. The study was carried out on laboratory scale using two MBBR reactors fed with synthetic wastewater. The wastewater was prepared by mixing a solution of molasses with a known amount of phenol and nutrients. Two MBBR units were operated simultaneously at different hydraulic retention times (HRT) of 24, 20, 16, 12 and 8 h while phenol concentration was in the range of 200, 400, 620 and 800 mg/l. Throughout the experiments the ratio of phenolic chemical oxygen demand (COD) concentration to total COD was changed from a ratio of 0.2 to a ratio of 1. The... 

The performance of a rotating biological contactor (RBC) for posttreatment of the slaughterhouse effluent from an upflow anaerobic sludge blanket (UASB) reactor was investigated in this study. The 280-L, six-stage RBC pilot plant was operated at different organic loading rates (OLRs) and biodisk speeds. The overall removal efficiencies for soluble biochemical oxygen demand (SBOD), total biochemical oxygen demand (TBOD), and total chemical oxygen demand (TCOD) decreased with increasing OLRs. Disk rotational speed did not have a significant effect on performance in the range studied. The results showed that satisfactory posttreatment to meet regulatory requirements for agricultural purposes... 

The objective of present study is to analyze the dynamic modeling of bioelectrochemical processes and improvement of the performance of previous models using quantitative data of bacterial transport parameters. The main deficiency of previous MFC models concerning spatial distribution of biocatalysts is an assumption of initial distribution of attached/suspended bacteria on electrode or in anolyte bulk which is the foundation for biofilm formation. In order to modify this imperfection, the quantification of chemotactic motility to understand the mechanisms of the suspended microorganisms’ distribution in anolyte and/or their attachment to anode surface to extend the biofilm is implemented... 

Pharmaceutical waste has attracted significant attention in the past two decades due to the current high consumption of pharmaceuticals together with the development of reliable detection technologies. In order to acquire better understanding on pharmaceuticals removal in biological processes, the treatment of synthetic wastewater containing diclofenac (DFN) and ibuprofen (IBU), two of the most commonly prescribed medicines worldwide, was studied using a moving bed biofilm reactor (MBBR). An 8.5-L aerobic MBBR with Kaldnes packing filling ratio of 40% was designed. The controlled parameters were pH within neutral range, temperature of 37 °C, mixed liquor suspended solids (MLSS) of 2100 mg/L,... 

One of the antibiotics used to treat infections is streptomycin sulfate that inhibits both Gram-negative and -positive bacteria. Nanoparticles are suitable carriers for the direct delivery and release of drug agents to infected locations. Niosomes are one of the new drug delivery systems that have received much attention today due to their excellent biofilm penetration property and controlled release. In this study, niosomes containing streptomycin sulfate were prepared by using the thin layer hydration method and optimized based on the size, polydispersity index (PDI), and encapsulation efficiency (EE%) characteristics. It was found that the Span 60-to-Tween 60 ratio of 1.5 and the... 

A laboratory-scale multistage anaerobic biofilm reactor of three compartments with a working volume of 54-L was used for treating a synthetic medium-strength wastewater containing molasses as a carbon source at different influent conditions. The start-up period, stability and performance of this reactor were assessed at mesophilic temperature (35 °C). During the start-up period, pH fluctuations were observed because there was no microbial selection or zoning, but as the experiment progressed, results showed that phase separation had occurred inside the reactor. COD removal percentages of 91.6, 91.6, 90.0 and 88.3 were achieved at organic loading rates of 3.0, 4.5, 6.75 and 9.0 kg COD/m3 day,... 

In this study, two moving-bed biofilm reactors (MBBR1 and MBBR2) filled with different size of carrier media (Kaldnes K1 and Kaldnes K1 micro, respectively) were subjected to soluble (sugar and sodium acetate (Ac)) substrate and mixture of soluble and particulate (particulate potato starch (PS)) substrate in a very high organic loading rate (12 kgCOD/m3·d) at different temperatures (26 and 15°C, in MBBR1 and MBBR2, respectively). The effects of carrier type and substrate on biofilm structure and reactor performance have been studied. Starch was removed by adsorption at the biofilm surface and hydrolyzed which caused substrate gradient in MBBR1, however, hydrolyzed uniformly within biofilm in... 

Sludge handling is a common issue in all biological wastewater treatment methods. In this study, sonication technique as a state-of-the-art technology has been applied to a continuous MBBR system with the aim of sludge reduction. A novel configuration of MBBR with an additional recycle stream of sonicated sludge was used as the experimental setup. Based on exposed energy and sludge disruption performance, optimized sonication density and exposure time were obtained 1.5 W/mL and 15 min, respectively. This condition provided 42.2% increase in soluble COD as a result of sludge disintegration. Our results revealed that the performance of MBBR and excess sludge reduction were affected by... 

The present study aimed at investigating the biological treatment of nitrogen and phosphorus from the saline wastewater in various systems. In the end, moving bed biofilm reactor and anaerobic/anoxic/aerobic (AOA) were chosen as the best systems. In the present study, the investigations were carried out in two 24-h and 12-h retention times for three nitrogen concentrations, 200 mg/l, 300 mg/l, and 400 mg/l, two phosphorus concentrations, 14 mg/l and 20 mg/l, three Chemical oxygen demand (COD) concentrations, 800 mg/l, 1000 mg/l, and 1200 mg/l, and four salt concentrations, 10 g/l, 12 g/l, 17 g/l, and 20 g/l. The obtained results indicated that the COD removal percentage was high in a range...