Influent Organic Concentration Research Articles

A powerful strategy to improve aerobic granular sludge stability towards organic shock loadings with varying carbon/nitrogen ratios: Weak magnetic field

The organic shock loadings with varying ratios of carbon to nitrogen (C/N) caused by fluctuations of wastewater flowrate and concentration inflict a great threat on the stability of aerobic granular sludge (AGS) in practical applications. Herein, the present work proposed an enhanced shock-loading-tolerance strategy for AGS by applying a weak magnetic field (WMF). Results indicated that aerobic granules exposed in WMF kept a significant propagation regardless of the various influent organic concentrations, while those in the control reactor exhibited inadaptability with decreasing biomass concentration and bioactivity at lean substrate conditions. The enhanced extracellular polymeric substances regulating process might be one of the inducement mechanisms to cope with organic shock loadings of WMF. In addition, the AGS system in WMF showed its strong resilience in terms of the ammonia and phosphate removal. Magnetic field could inhibit the overgrowth of filamentous bacteria, and the enhanced tolerance for organic shock loadings might attribute to the enrichment of functional microbes related to structural stability such as Firmicutes and Candidatus_Competibacter. Therefore, this work revealed the enhanced mechanisms of magnetic field for improving the AGS stability towards organic shock loadings, promoting the full-scale engineering applications of both AGS and magnetization technologies in wastewater treatment.

Physico‐Chemical and Kinetic Evaluation of a Combined Vertical Settler/Self‐Aerated Unit for Wastewater Treatment and Reuse

AbstractWater resource limitation is one of the crises facing many countries worldwide. The work aims to apply a compact unit consisting of a vertical settler (VS) followed by a self‐aerated chamber (SAC) for wastewater treatment. The dimensions of the unit are 2 × 1 × 2.5 m for length, width, and height, respectively. The hydraulic retention time (HRT) is 5 h in the VS for performance study while for the kinetic study the HRT is 4, 6, 8, 10, to 12 h. The unit is packed with a non‐woven fabric material produced from waste plastic. The influent organic concentrations expressed by chemical and biological oxygen demand (CODtot and BOD) are 367.7 and 254.7 mg L−1, respectively. The concentrations of CODtot and BOD in the treated effluent are 78.8 and 80.5% to 36.7 and 16.6 mg L−1, respectively. The prevailed removal kinetic for COD and nitrogen (N) concentrations is the second‐order reaction kinetic. With the exception of fecal coliform (FC), the final treated effluent meet the National regulatory requirements. The disinfection step is essential to reuse the final treated effluent safely. The unit can serve 100 p.e. in rural and unserved areas in developing countries with area of 2–3 m2.

Deactivation mechanism of calcified anaerobic granule: Space occupation and pore blockage

Calcification and deactivation of high rate sludge bed reactors is a common and serious engineering problem in the application of anaerobic bioreactor. In this study, the characteristics and deactivation mechanism of calcified anaerobic granules were investigated. The results showed that the calcium content of calcified anaerobic granules was ten times higher than that of control anaerobic granules. A large part of the calcium accumulated in the center of anaerobic granules in the form of calcite, and a small part of the calcium distributed in the outer layer of anaerobic granules in the form of Ca-P deposit. The calcium core occupied a large space which was available for the functional microorganisms. The calcium salts deposited in the outer layer of granular sludge which led to the significant reduction of macropore volume. The porosity of calcified anaerobic granules decreased by 13% compared with that of control anaerobic granules, causing generally the decline of methanogenic activity (for example, by 13% at influent organic concentration of 6.6 g COD L−1). The substrate gradient created by methanation of organic salts, including organic calcium salts, was deduced to be the driving force of anaerobic granule calcification, while the gradual accumulation of calcium salts in anaerobic granules was deduced to be the dominant factor for the decline of anaerobic granule activity.

Integrated experimental investigation and mathematical modeling of a membrane bioelectrochemical reactor with an external membrane module

Membrane bioelectrochemical reactors (MBERs) integrate membrane filtration module into microbial fuel cells (MFCs) to achieve silmultaneous wastewater treatment, bioenergy production, and high-quality effluent. Previous MBERs usually have membrane modules as a part of the MFC reactors that creates challenges for membrane cleaning. In this study, an MBER with an external membrane module was investigated through both experiments and mathematical modeling. This MBER produced a current density of 7.1±0.5Am−3 with an anolyte recirculation of 90mLmin−1; reducing the anolyte recirculation rate had a negligible effect on MBER’s electrical performance but resulted in a positive energy balance of 0.003±0.002kWhm−3. Periodic backwashing (1min-backwashing/15min-operation) was demonstrated as an effective method for fouling control. A mathematical model was developed and validated using the experimental data. The model could predict the influence of key parameters such as influent organic concentration and anolyte flow rate on the current generation, and identify the maximum organic loading rate for current generation. Those results encourage further investigation and development of this MBER toward system scaling up.

Optimization of three-stage Anammox system removing nitrogen from landfill leachate

Advanced nitrogen removal had been realized from mature landfill leachate via three-stage anaerobic ammonium oxidation (Anammox) system during the previous study. However, the Anammox system was influenced by factors such as influent nitrite and organic concentrations and needed to be optimized. To optimize the Anammox system, this study investigated Anammox Sequence Batch Reactor (ASBR) with different feeding modes and influent organic concentrations. The results showed that with influent ammonia and nitrite concentrations of 250±20 and 320±20mg/L, respectively, a continuous feeding mode reduced the adverse effect of high influent nitrite concentration on Anammox. A small amount of organics improved rather than inhibited nitrogen removal. However, as influent COD increased (from 600±50 to 800±50mg/L), Anammox was gradually inhibited. Influent organics concentration should be kept below 800mg/L, which facilitated Anammox.

Microbial population dynamics during aerobic sludge granulation at different organic loading rates

Laboratory experiments were carried out to investigate the evolution of the bacterial community during aerobic sludge granulation. The experiments were conducted in three 2.4 L sequencing batch reactors (SBRs) that were seeded with activated sludge and fed with glucose-based synthetic wastewater. Three different influent organic concentrations were introduced into the three SBRs, R1, R2 and R3, resulting in chemical oxygen demand (COD) loading rates of 1.5 (R1), 3.0 (R2) and 4.5 (R3) kg/m 3 d, respectively. Changes in bacterial diversity throughout the granulation process were monitored and analysed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The experimental results demonstrate that glucose-fed aerobic granules could be formed without significant presence of filamentous bacteria. Granules formed at different loading rates had different morphology, structural properties and bacterial species. A higher loading rate resulted in faster formation of larger and loose granules, while a lower loading rate resulted in slower formation of smaller and more tightly packed granules. The biomass underwent a dynamic transformation in terms of bacterial species richness and dominance during the granulation process. The reactor with the highest substrate loading rate had the lowest species diversity, while the reactor with the lowest substrate loading rate had the highest species diversity. Different dominant species of β- and γ-Proteobacteria and Flavobacterium within the granule communities from the three different SBRs were confirmed by analysis of 16S rDNA sequences of the PCR products separated by DGGE. It is apparent that a few common bacterial species play an important role in the formation and growth of aerobic granules and help sustain the granular sludge structure in the bioreactors.

Performance evaluation and mathematical modelling of granular activated carbon biofiltration in wastewater treatment

Biological filtration is an effective technique for removing organic matter from wastewater. The perfor- mance of a biofilter can be influenced by a range of operational conditions. In this study the performance of biofilters was investigated for the influence of filter media depth, influent concentrations, filtrations rates and backwashing. The results show that performance of GAC filters decreased with shallower filter bed depths. In addition, the GAC per- formed better at lower influent concentration and lower filtration rates. The daily backwash adopted to avoid the phys- ical clogging of the biofilter did not have any significant effect on the organic removal efficiency of the filter. The con- centration, activity and characteristics of the biomass are quantified and described. A mathematical model was devel- oped to simulate the organic removal of the GAC biofiltration system. The performance of the GAC filter under dif- ferent influent organic concentration levels, filtration rates and filter bed depths was adequately simulated by the math- ematical model developed for this study.

Mathematical Model and Mechanisms for Biofilm Wastewater Treatment Systems

Fundamental theoretical depiction is still lacking on biofilm wastewater treatment systems up to today. A mathematical model of biofilm wastewater treatment systems, taking account of suspended microorganisms and some factors influencing biofilm formation and stabilization, is developed in this paper. By theoretical and numerical analyses, the factors influencing biofilm formation and stabilization, such as the dilution rate, influent organic concentration, detachment and initial inoculum concentration etc, are discussed. Qualitative investigations were carried out and suggestions on industrial applications are then proposed. This paper not only plays an important role in understanding the physical mechanisms of biofilm dynamics, but also has far-reaching implications for industrial practices.

Kinetic analysis of an anaerobic filter treating soybean wastewater

An investigation into the kinetics of the treatment of soybean wastewater in an anaerobic filter is described. The substrate loading removal rate was compared with predictions from a modified Stover–Kincannon model, the Monod model and a regression relationship. The modified Stover–Kincannon model produced the best fit with the experimental results. The modified Stover–Kincannon model could also be used to determine the reactor volume required to decrease a set influent organic concentration to a given effluent concentration, or to determine the effluent substrate concentration for a given volume of an anaerobic filter and influent organic concentration. The overall reaction order in the anaerobic filter treating soybean wastewater appeared to be close to half order. The methane production kinetics could be described by a similar relationship that used to describe the organic substrate removal kinetics of the anaerobic filter treating soybean wastewater. The kinetic relationships derived from the lab-scale experiment provided good estimates of the performance of pilot- and full-scale anaerobic filters packed with the same media and treating the same wastewater in terms of the effluent chemical oxygen demand (COD) concentrations and the specific methane production rates.

Significance and establishment of adequate transition periods in wastewater experimentation

Abstract Five categories of transitions following changes in influent organic concentration, HRT and SRT in wastewater experimentation were examined under conditions of controlled flow rates. The relationships between transition periods, biological parameters and effluent responses were also studied. Experimental results showed that Danckwert's residence time distribution model predicts adequately the length of transition required when changes in SRT at constant HRT are made. However, it is an inadequate estimator of equilibrium when influent organic concentration or HRT changes are imposed on the system at constant SRT. Monitoring the establishment of a steady level of MLVSS and other biological and response parameters is required to ensure that data collected for performance analysis will be representative of the new operating conditions.

Practical application of statistics for the monitoring and interpretation of waste treatment process performance

Abstract Appropriate statistical tests were used to facilitate the interpretation of data and maximize the information gathered from the analysis of the operation and behaviour of a biological system under dynamic conditions. SRT and HRT were found not only to exert independent effects on responses but also to interact significantly. Influent organic concentration was found to affect responses by way of interaction effects and must be taken into consideration when interpreting performance data.