Model development and parameter estimation for a hybrid submerged membrane bioreactor treating Ametryn

A Mechanistic Model for Hydrogen Production in an AnMBR Treating High Strength Wastewater

In the global race to produce green hydrogen, wastewater-to-H2 is a sustainable alternative that remains unexploited. Efficient technologies for wastewater-to-H2 are still in their developmental stages, and urgent process intensification is required. In our study, a mechanistic model was developed to characterize hydrogen production in an AnMBR treating high-strength wastewater (COD > 1000 mg/L). Two aspects differentiate our model from existing literature: First, the model input is a multi-substrate wastewater that includes fractions of proteins, carbohydrates, and lipids. Second, the model integrates the ADM1 model with physical/biochemical processes that affect membrane performance (e.g., membrane fouling). The model includes mass balances of 27 variables in a transient state, where metabolites, extracellular polymeric substances, soluble microbial products, and surface membrane density were included. Model results showed the hydrogen production rate was higher when treating amino acids and sugar-rich influents, which is strongly related to higher EPS generation during the digestion of these metabolites. The highest H2 production rate for amino acid-rich influents was 6.1 LH2/L-d; for sugar-rich influents was 5.9 LH2/L-d; and for lipid-rich influents was 0.7 LH2/L-d. Modeled membrane fouling and backwashing cycles showed extreme behaviors for amino- and fatty-acid-rich substrates. Our model helps to identify operational constraints for H2 production in AnMBRs, providing a valuable tool for the design of fermentative/anaerobic MBR systems toward energy recovery.

Evaluation of membrane cake fouling mechanism to estimate design parameters of a submerged AnMBR treating high strength industrial wastewater

A mathematical model, which was previously developed for submerged aerobic membrane bioreactors, was successfully applied to elucidate the membrane cake-layer fouling mechanisms due to bound extracellular polymeric substances (eEPS) in a submerged anaerobic membrane bioreactor (SAnMBR). This biofouling dynamic model explains the mechanisms such as attachment, consolidation and detachment of eEPS produced in the bioreactor on the membrane surface. The 4th order Runge-Kutta method was used to solve the model equations, and the parameters were estimated from simulated and experimental results. The key design parameters representing the behaviour of cake fouling dynamics were systematically investigated. Organic loading rate (OLR) was considered a controlling factor governing the mixed liquor suspended solids (MLSS), eEPS production, filtration resistance (R_t), and transmembrane pressure (TMP) variations in a SAnMBR. eEPS showed a proportional relation with OLR at subsequent MLSS variations. The consolidation of EPS increased the specific eEPS resistance (α_s), influencing the cake resistance (R_c). The propensities of eEPS showed a positive correlation with R_t and TMP. The outcomes of the study also estimated a set of valuable design parameters which would be vital for applying in AnMBRs treating industrial wastewater.

AVALIAÇÃO DOS SUBPRODUTOS DE DEGRADAÇÃO DO HERBICIDA AMETRINA OBTIDOS VIA PROCESSOS OXIDATIVOS AVANÇADOS

As tecnologias alternativas, como os processos oxidativos avançados (POA), contribuem para o controle das poluições ambientais e nesse contexto uma das informações mais importantes é a determinação dos subprodutos de degradação formados em cada condição de estudo. Nesse trabalho foram avaliadas diferentes concentrações de H2O2, pH e temperatura, sempre com o objetivo de promover a quebra da molécula do herbicida triazínico ametrina e avaliar os principais subprodutos formados no processo de degradação. O maior número de subprodutos foi identificado utilizando a espectrometria de massas com inserção direta nas condições com 20% e 25% de H2O2 a 65 ºC, sendo detectados 5 possíveis compostos originados a partir da fragmentação da molécula original da ametrina.

New and practical mathematical model of membrane fouling in an aerobic submerged membrane bioreactor

This study aimed to develop a practical semi-empirical mathematical model of membrane fouling that accounts for cake formation on the membrane and its pore blocking as the major processes of membrane fouling. In the developed model, the concentration of mixed liquor suspended solid is used as a lumped parameter to describe the formation of cake layer including the biofilm. The new model considers the combined effect of aeration and backwash on the foulants' detachment from the membrane. New exponential coefficients are also included in the model to describe the exponential increase of transmembrane pressure that typically occurs after the initial stage of an MBR operation. The model was validated using experimental data obtained from a lab-scale aerobic sponge-submerged membrane bioreactor (MBR), and the simulation of the model agreed well with the experimental findings.

Performance of a laboratory-scale membrane bioreactor consisting mixed liquor with aquatic worms under toxic conditions

A laboratory scale membrane bioreactor (MBR) consisting of worms was operated for 214days. The objective was to evaluate the treatment and operating performance of the MBR with and without the addition of Ametryn which is a toxic and persistent herbicide. Removal of Ametryn was doubled (up to 80%) in the MBR when the worms were present. Increased rate (2.5kPa/day) of trans-membrane pressure (TMP) and low concentration of MLSS (5.5g/L) were recorded when the worm population was high (80-100 worms per 70μL). Short-term critical flux values were increased from 7.5 to 15 and then to 30L/m(2)/h when the worm numbers decreased from 90 to 35 and then to 18 per 70μL of mixed liquor respectively. Further, high levels of carbohydrate concentration of soluble microbial products (SMP) and smaller sludge floc-sizes were found when the worm numbers were high.