In the mixture study, more than 94 % total degradation of the EDPs was achieved at initial DMP and DEP concentrations of 2000 and 1500 mg/L, respectively. Fed-batch operation with the reactor further revealed 82.87 % degradation efficiency of the EDPs mixture even at their high initial concentrations.
List of Figure
Biomass growth and degradation profile of phthalate mixtures for different total initial concentrations of (a) 750, (b) 1250 and (c) 1500 mg/L in the batch controlled CSTB. Biomass growth of Cellulosimicrobium funkei and EDP's biodegradation profile in the TPPB system operating in batch mode: (a) single substrate (DEP) and (b) mixed substrate (DMP and DEP).
List of Table
Glossary of Acronyms
List of Notations
Introduction and
Review of literature Chapter 1
Introduction
Contamination by these pollutants in groundwater, open water bodies, and the soil environment are interconnected and lead to adverse effects on aquatic organisms and human health problems when they become part of the ecosystem (Daughton, 2010; Kanaujiya et al., 2019). Among these pollutants, phthalic acid esters (PAEs) have been identified as emerging environmental pollutants due to their prevalence in various ecological systems (Figure 1.1) (Das et al., 2021; Zarean et al., 2019).
Phthalic acid esters
- Physicochemical properties of PAEs
- Application of PAEs
- Fate and occurrence of PAEs in the environment
Other sources of PAE include wastewater treatment plants and leachate from landfills, industrial waste streams, and septic tanks (Schaider et al., 2016; Sui et al., 2015). Domestic wastewater is another primary source of many of the PAEs, such as pharmaceuticals, personal care products, and household products containing PAEs (Luo et al., 2014b).
Industrial Activities and Hospitals
PAEs enter the environment through various routes such as losses from production processes, weathering, leaching or evaporation from finished products. The emission rate of a specific phthalate to the environment is influenced by its equilibrium gas-phase concentration, which is controlled by its concentration in the source and its vapor pressure (Liang and Xu, 2014).
Households
They are often adsorbed to particles after being released into the environment and are transported through a variety of pathways, including atmospheric transport, agricultural runoff, leaching from landfills, discharge from wastewater treatment plants, before finally reaching even the most remote environments (Gao et al., 2014). ). KOA for PAE indicates their partitioning between air and organic phase in atmospheric aerosols, plants and soil.
Wastewater Treatment
Moreover, their occurrence is not restricted within a specific environmental compartment which is controlled by their physico-chemical properties and environmental factors such as vapor pressure (VP), octanol-water (KOW), octanol-air (COA) and air-water (KAW). ) partition coefficients (Kashyap and Agarwal, 2018).
Plants
Animal Farming Activities
Treatment Plants
Agricultural Activities
Groundwater Aquaculture
Surface Water
Exposure to PAEs
Exposure to phthalates such as DEP and DBP, which are often present in various cosmetic products including nail polish, deodorant, perfume, hair gels, hair sprays, body lotion, etc., is through inhalation and dermal contact (Eichler et al., 2019; Pang et al.). et al., 2021). DBP and DEP are used in eudragit for effective drug delivery in the human gastrointestinal tract (Thakral et al., 2012).
Toxic effect of PAEs
Additionally, PAEs have been claimed to have adverse effects on the liver and testes, in addition to their effects on the kidneys and thyroid (Tuan Tran et al., 2022). Furthermore, exposure to phthalates is associated with cardiovascular risk factors such as high blood pressure, atherosclerosis, and coronary heart disease (Mariana et al., 2016; Olsén et al., 2012).
Treatment of PAEs containing wastewater
- Physicochemical treatment processes
- Sorption process
- Coagulation/flocculation
- Advanced oxidation processes
- Biological treatment processes
- Microbiological aspects of PAEs degradation
- Conventional biological treatment systems 1. Activated sludge process
- Advanced biological treatment systems 1. Membrane-based bioreactor
Strong oxidants can degrade a wide range of organic pollutants (Mansouri et al., 2019; Sudhakaran et al., 2013b). Such isolates degraded DMP, DEP and DBP more easily (Chen et al., 2015).
Definition of problem
Aim and objectives
Biodegradation of dimethyl phthalate and diethyl phthalate by Cellulosimicrobium funkei in a batch system: kinetics and
Introduction
Some EDPs also enter the atmosphere through untreated sewage containing such compounds (Bergman et al., 2012). PAEs and their metabolites are toxic, hepatotoxic, teratogenic, carcinogenic, mutagenic and potential endocrine disruptors (Khadka et al., 2020).
- Screening of microorganisms
- Dual substrate system
- Modeling of EDPs biodegradation kinetics
- Analytical methods
- Morphological analysis of biomass through FESEM
- Biomass estimation
- Determination of DMP and DEP
- Identification of metabolic intermediates
The bacterium was initially grown in MSM containing 500 mg/L DMP and DEP as a single substrate for 24 h at 30 °C. The specific degradation rate (qs in mg/mg·h) of the compounds was calculated for each initial concentration. To analyze DMP and DEP concentrations, samples collected during the experiments were first extracted with an equal volume of dichloromethane and allowed to air dry at room temperature to allow the solvent to evaporate.
Results and discussion
- Screening of microorganisms
The lag phase in biomass growth and degradation of EDPs was also prolonged due to the increase in their initial concentration (Figures 2.4 and 2.5). Above this concentration, the value decreased gradually and at the initial concentration of 3500 mg/L the growth of biomass as well as the degradation of EDPs stopped completely. This sharp decrease in biomass growth and degradation of DMP at a high initial concentration is attributed to the toxic effect of DMP on C.
Time (h)
Modeling of biodegradation kinetics of DMP and DEP
For a better understanding of the biodegradation kinetics involved, the experimental data were fitted to different kinetic models reported in the literature. The other models (Aiba, Andrew and Webb) although fitted the experimental data well with high R2 values and low SSE values, the estimated qmax values were much higher than the experimentally obtained value. Differences in the accuracy of different models to predict experimental data are attributed to the fact that these models were originally derived to describe the degradation of different substrates by EDPs using different microorganisms (Arutchelvan et al., 2006).
Substrate conc. (mg/L)
Biodegradation of DMP and DEP as dual substrates using C. funkei
The biodegradation efficiency values of EDP in different experimental series are shown in Figure 2.10, and the values presented in Table 2.1 reveal that the degradation of DMP and DEP in the mixture varied in the range and depended mainly on their initial concentrations in the mixture. 3, 5 and 7 (total initial concentration of EDP = 3000 mg/L), their degradation efficiency value decreased with increasing concentration of DEP;. 6 and 8 with a total initial concentration of 3500 mg/L, the degradation efficiency of DMP/DEP decreased to less than 40%, while at a total initial concentration of 4000 mg/L, no degradation was observed in the mixture.
Conclusion
Similarly, Prasad and Suresh (2015) studied the degradation of a mixture of DMP, DEP and DBP, each with an initial concentration of 100 mg/L and obtained 100% degradation by Variovorax sp.
Biodegradation and toxicity removal of dimethyl phthalate and diethyl phthalate by Cellulosimicrobium funkei in a continuous
Introduction
Phthalic acid esters (PAE) are semi-volatile chemicals and are used in the production of soft and flexible plastics or as dissolving agents for various types of materials (Huang et al., 2021). In particular, dimethyl phthalate (DMP) and diethyl phthalate (DEP) are often added to commercial plastics and epoxy resins to improve their properties such as flexibility, durability and adhesion, and are therefore also known as plasticizers (Tao et al., 2019b). Due to the lack of suitable substitutes, the consumption of PAEs in a wide range of industries seems inevitable in the future (Huang et al., 2021).
- Microorganism, culture conditions and media composition
- Biodegradation experiments using CSTB under different operation mode 1. Batch operation mode
- Continuous operation mode
- Tubular ceramic membrane for microfiltration of biomass 1. Fabrication of membrane
- Characterization of the prepared membrane
- Continuous biodegradation under biomass recycle mode
- Analytical methods
- Ecotoxicity of the treated water 1. Phytotoxicity evaluation
- Brine shrimp mortality bioassay
The operating parameter of the reactor was kept the same as in the batch experiments. The dry weight of the membranes (Wb) was measured before immersion in acid/base solution. For this test, the dry weight of the membrane was measured before immersion in water for 24 hours.
Results and discussion
- Degradation under batch operation mode 1. Single substrate system
- Dual substrate system
- Degradation under fed-batch operation mode
- Degradation under continuous operation
- Characterization of prepared membrane
- Continuous biodegradation under biomass recycle mode
- Ecotoxicity assessment 1. Seed germination
- Brine shrimp mortality
The time profile of biodegradation of DMP and DEP in single- and dual-substrate systems along with biomass growth in a batch-fed CSTB is shown in Figure 3.6. While, with increasing ILR, the degradation rate and degradation efficiency of the compounds decreased due to the inhibition of microbial activity (Figure 3.8a and b). Chickpea seeds soaked in different samples taken before and after DMP and DEP degradation and in distilled water are presented in Figure 3.14.
Conclusion
Biodegradation and toxicity removal of a mixture of low and high molecular weight endocrine disrupting phthalates by
Introduction
Phthalate esters (PEs) are typical synthetic organic compounds grouped into EDCs and are mostly synthesized by esterification of the corresponding alcohol and phthalic acid (Hu et al., 2021a). The massive consumption and production of plasticizers poses a serious risk to humans, animals and aquatic organisms due to exposure to PAEs through dermal contact, ingestion and inhalation (Kanaujiya et al., 2019). Several treatment strategies have been proposed to protect human and animal health and the environment from the adverse effects of PAEs, such as physical, chemical, advanced oxidation processes, and microbial degradation, or combinations of these techniques (Xiaoyan et al., 2015).
- Culture conditions
- Biodegradation of mixture of 6 EDPs in CSTB 1. Batch experiments
- Fed-batch experiments
- Continuous experiments
- Continuous experiments with biomass recycle
- Ecotoxicity of the treated water
- Analytical methods
The details of fabrication and characterization of the tubular ceramic membrane used in this study are the same as previously mentioned in Chapter 3 under section 3.2.4. The reactor was initially operated batchwise with a total initial concentration of phthalates mixture of 750 mg/L and was switched to continuous mode of operation at the end of the initial batch operation (96 hours). Based on the results of the previous continuous experiments with the CSTB, 36 hours HRT and 1500 mg/L total concentration of phthalate mixture were chosen for this continuous biomass recycling study, since the biodegradation efficiency was not satisfactory in the continuous mode of operation.
Results and discussion
- Degradation of EDPs mixture and biomass growth in CSTB 1. Batch operated CSTB
- Fed-batch operated CSTB
- Continuous operated CSTB
- Continuous operation with biomass recycle
- Ecotoxicity study of treated water 1. Seed germination bioassay
- Brine shrimp lethality bioassay
Compared to the biodegradation of phthalates mixture in a previous batch shake flask study, these values are much higher in the CSTB. Therefore, to overcome the inhibitory effect of the phthalates at a high initial concentration, the bioreactor was started with a low total initial concentration of phthalates mixture, i.e. The results of the bioreactor experiments conducted in continuous mode with recycling of biomass are shown in Figure 4.7, which shows the biomass concentration (mg/L), inlet - outlet phthalate concentrations (mg/L) and phthalate biodegradability (%) efficiency profiles with time (h).
Conclusion
Biodegradation and toxicity removal of dimethyl phthalate and diethyl phthalate by Cellulosimicrobium funkei in two-phase
Introduction
A critical environmental concern due to PAEs is their persistence in the ecosystem over a long period of time due to their high hydrophobicity and low volatility (Sharma et al., 2021). Frequent exposure to phthalates is associated with toxic effects in humans and wildlife (Ahmad et al., 2017; Kambia et al., 2015). Furthermore, due to the hydrophobicity and low aqueous solubility of PAEs, their bioavailability to microbes is seen as a barrier to their biodegradation in natural as well as engineered treatment systems (Josh et al., 2014).
Materials and methods 1. Chemicals and solvents
- Bacterial culture conditions
- Two phase partitioning bioreactor (TPPB) experiments 1. Selection of non-aqueous phase liquid
- Effect of volume fraction of silicone oil on DEP biodegradation
- Effect of NAPL on oxygen transfer in stirred tank reactor
- Biodegradation of DEP and DMP in TPPB 1. Batch experiments
- Analytical methods
- Ecotoxicity of the degraded phthalates 1. Phytotoxicity evaluation
- Brine shrimp lethality bioassay
The physical dimensions and other features of the CSTB used in this study are mentioned in Chapter 3 under section 3.2.3.1. The residual concentration of DMP and DEP in the extracted methanol sample was determined by the same protocol as followed for the aqueous phase determination of EDPs. To evaluate the removal of toxicity of DEP and DMP due to their degradation by C.
Results and discussion
- Selection of organic solvent as NAPL in the TPPB system
- Effect of NAPL volume fraction on biodegradation
- Determination of volumetric oxygen mass transfer coefficient in the TPPB
- Fed-batch operation mode
- Ecotoxicity assessment of the degraded phthalates 1. Phytotoxicity
- Brine shrimp assay
Whereas, in the case of silicone oil and n-hexane as the NAPL, very low metabolic activity of C. Biodegradation profiles of DEP and DMP in the mixed substrate system, along with biomass growth of C. In the present study, the active brine shrimp nauplii were used to determine the toxicity removal due to biodegradation of phthalate by C. funkei in the TPPB system.
Conclusion
Summary and
Conclusions Chapter 6
However, using batch shake flask, a low degradation efficiency was achieved at high initial concentration of phthalates. Compared to the batch operation, the fed batch operation further revealed the high degradation efficiency of the DMP and DEP mixture, even at their high initial concentrations. Very high values of biodegradation efficiency of compounds by C. funkei were reported using the TPPB system.
Bibliography
Assessment of phthalate esters (PAE) and bisphenol A (BPA) concentration and genotoxic potential of treated wastewater (final effluent) in Saudi Arabia. Phthalate esters in the environment: A critical review of their occurrence, biodegradation and removal during wastewater treatment processes. Biodegradation of phthalic acid esters (PAE) and in silico structural characterization of mono-2-ethylhexyl phthalate (MEHP) hydrolase based on close structural homologue.
