Sandra Raquel Ramires Esteves

University of South Wales · Sustainable Environment Research Centre

Antibiotic resistant bacteria (ARB) and their genes (ARGs) have become recognised as significant emerging environmental pollutants. ARB and ARGs in sewage sludge can be transmitted back to humans via the food chain when sludge is recycled to agricultural land, making sludge treatment key to control the release of ARB and ARGs to the environment. Th...

Anaerobic digestion technology has seen a significant deployment at full scale in the last decade, especially in Europe. The technology can treat organic wastes (i.e. municipal, industrial and agricultural wastes). Degradation of organic material has the potential to generate odour emissions, which can be mitigated by the use of sealed vessels, com...

A biological methanation system based on nutrient recycling via mixed culture microbial catabolism was investigated at mesophilic (37 °C) and thermophilic (55 °C) temperatures. At mesophilic temperatures, the formation of biofilms on two different types of material was assessed. Results showed that with intense mixing the biofilm reactors presented...

The integration of a biomethanation system within a wastewater treatment plant for conversion of CO2 and H2 to CH4 has been studied. Results indicate that the CO2 could be utilised to produce an additional 13,420m(3)/day of CH4, equivalent to approximately 133,826kWh of energy. The whole conversion process including electrolysis was found to have a...

The performance of a novel biofilm plug flow reactor containing a mixed anaerobic microbial culture was investigated for the conversion of CO2/H2 to CH4. Unlike conventional gas-liquid contactors that depend on agitation, gas diffusion was decoupled from power consumption for mixing by increasing the gas phase inside the reaction space whilst incre...

In this paper, the biomineralization potential and cellular response of novel blend films of the anionic sulfated polysaccharides kappa-carrageenan (KCG) and fucoidan (FUC) derived from seaweeds with semi-crystalline polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHBV), respectively, were analyzed. The incorporation of KCG and FUC i...

A novel eco-engineered mixed anaerobic culture was successfully demonstrated for the first time to be capable of continuous regeneration in nutrient limiting conditions. Microbial catabolism has been found to support a closed system of nutrients able to enrich a culture of lithotrophic methanogens and provide microbial cell recycling. After enrichm...

The work assessed the use of shear viscosity at 0.1 s⁻¹ ( ) as a parameter to detect changes in the conditioning and dewatering of digestates. Total and soluble fractions of organic matter of digestate samples before and after storage were also assessed in regards to their conditioning and dewatering performance. Digestate from a conventional mesop...

The extracellular polymeric substances and microbial cytoplasmic contents seem to hold inorganic ions and organic products, such as proteins and carbohydrates that are of critical importance for the metabolism of hydrolytic and acidogenic anaerobic microorganisms. The addition of soluble microbially recovered nutrients from thermally treated digest...

Bone tissue engineering based on scaffolds is quite a complex process as a whole gamut of criteria needs to be satisfied to promote cellular attachment, proliferation and differentiation: biocompatibility, right surface properties, adequate mechanical performance, controlled bioresorbability, osteoconductivity, angiogenic cues, and vascularization....

The influence of acetate and butyrate enrichment on biofilm structure for enhanced electricity and hydrogen production was investigated using bioelectrochemical systems (BES). Two reactors were enriched for 9 weeks using 20 mM L−1 acetate (AC) and butyrate (BU) in microbial fuel cell mode before transfer into MECs. Acetate and butyrate (20, 10 and...

Microfiltration (MF) and electrodialysis (ED) were used to recover and concentrate volatile fatty acids (VFAs) and nutrients from anaerobic hydrolysates of thermally hydrolysed waste activated sludges. Results showed that most of VFAs in the hydrolysate were recovered by the MF because of their existence in salt form rather than free acid form. Hig...

The conditioning requirements and dewaterability as well as rheological properties of digestate continuously pumped from the digester to a holding tank in a waste water advanced anaerobic digestion plant have been investigated and compared. Results have shown that process conditions between digester and holding tank (i.e. aeration and/or storage ti...

In this study, volatile fatty acids (VFAs), which are by-products from anaerobic fermentations, have been used as the carbon source for polyhydroxyalkanoates (PHA) production by pure culture bacteria, Cupriavidus necator. A number of factors influence the conversion efficiencies of VFAs to PHAs including the bacterial feeding regimes. When VFA was...

Titration methodologies have been used for the many years for low cost routine monitoring of full scale anaerobic digestion plants. These methodologies have been correlated to indicate the carbonate alkalinity and the volatile fatty acids (VFA) content within digesters. Two commonly used two end-point titration methods were compared using a dataset...

Environmental burdens associated with small scale (40 L hydrogen per minute) production of hydrogen fuel using electrolysis powered by electricity generated from stand-alone wind turbines (30 kW), stand-alone photovoltaic panels (3 kW peak) and UK grid electricity (current and future) has been undertaken. Utilization of fuel within a proton exchang...

External stress factors in the form of ionic species or temperature increases have been shown to produce a stress response leading to enhanced PHA production. The effect of five different NaCl concentrations, namely 3.5, 6.5, 9, 12 and 15 g/l NaCl on PHA productivity using Cupriavidus necator has been investigated alongside a control (no added NaCl...

The production of polyhydroxyalkanoates (PHAs) using digestate liquor as culture media is a novel application to extend the existing uses of digestates. In this study, two micro-filtered digestates (0.22 μm) were evaluated as a source of complex culture media for the production of PHA by Cupriavidus necator as compared to a conventional media. Cultu...

The production of polyhydroxyalkanoates (PHAs) using digestate liquor as culture media is a novel application to extend the existing uses of digestates. In this study, two micro-filtered digestates (0.22μm) were evaluated as a source of complex culture media for the production of PHA by Cupriavidus necator as compared to a conventional media. Cultu...

This first international proficiency-testing scheme evaluated the analytical performance and the state of practice in measurement of volatile fatty acids in aqueous samples. Gas chromatography and high-performance liquid chromatography were used by 25 laboratories from 15 different countries. Two reference materials were selected for analysis. The...

Microbial populations in a full-scale anaerobic digester fed on food waste were monitored over an 18-month period using qPCR. The digester exhibited a highly dynamic environment in which methanogenic populations changed constantly in response to availability of substrates and inhibitors. The methanogenic population in the digester was dominated by...

In this study, dielectric spectroscopy was utilised to evaluate and define the optimum harvesting time for polyhydroxyalkanoates (PHA) production. It is essential to harvest PHA at the optimum time during fermentation for maximum yield, otherwise cells start degrading. Two carbon sources (acetic and butyric acids) were used in laboratory based expe...

This study investigates the use of Hotelling's T2 control charts as the basis of a process monitor for sewage sludge anaerobic digestion. Fourier transform near infrared spectroscopy was used to produce partial least squares regression models of volatile fatty acids, bicarbonate alkalinity and volatile solids. These were utilised in a series of pri...

Anaerobic bioprocesses such as Anaerobic digestion (AD), fermentative biohydrogen (BioH(2)), and Bioelectrochemical system (BES), converting municipal, agro-industrial wastes and crops to energy have attracted accelerating interest. Anaerobic digestion (AD) however, still requires optimisation of conversion efficiency from biomass to methane. Augme...

A fast and cost effective immobilization of electron carriers, methylene blue (MB) and neutral red (NR) by pH shift was proposed to improve bioanodic performance. The adsorption of mediators onto the carbon cloth anode was verified using cyclic voltammogram (CV) and the effect of the immobilized mediators on acclimation, power density, and acetate...

Waste activated sludge (WAS) is difficult to degrade in anaerobic digestion systems and pretreatments have been shown to speed up the hydrolysis stage. Here the effects of acid pretreatment (pH 6-1) using HCl on subsequent digestion and dewatering of WAS have been investigated. Optimisation of acid dosing was performed considering digestibility ben...

This study investigates the use of Fourier transform near infrared (FT-NIR) spectroscopy combined with principle components analysis (PCA) and partial least squares regression (PLS-R) as part of a possible process monitoring system for sewage sludge anaerobic digesters. The ability of FT-NIR with PCA to distinguish between different stages of the A...

Microbial electrolysis cells (MECs) could be integrated with dark fermentative hydrogen production to increase the overall system yield of hydrogen. The influence of catholyte pH on hydrogen production from MECs and associated parameters such as electrode potentials (vs Ag/AgCl), COD reduction, current density and quantity of acid needed to control...

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT...

The IWA Anaerobic Digestion Model No.1 (ADM1) has been extensively used in recent years. However, its application to non-methanogenic systems is limited by the use of constant-stoichiometry to describe product formation from carbohydrate fermentation. This study presents a modification of the ADM1 using a variable stoichiometry approach, derived fr...

A numerical evaluation of the energy available from biomass-derived transport fuels, including biodiesel, bioethanol, and biomethane has been undertaken based on the available literature. The evaluation focuses on the energy balance, co-products, and tailpipe emissions of the fuels. Biomethane from the anaerobic digestion of crops was found to have...

Parameters monitored on-line in a laboratory biological wastewater plant treating simulated textile effluent were examined for use in a control strategy. The plant, an anaerobic (UASB) reactor with an aerobic stage and overall HRT 1.8 days, was operated at steady-state and transient conditions with varying ratios of azo dye and starch. Gas flow rat...

Combined anaerobic–aerobic treatment was used to treat a simulated textile industry wastewater (overall HRT 1.8 days). The azo dye (PROCION Red H-E7B) and starch concentrations were varied in a series of 1-week experiments to determine the effect of starch:dye ratio on COD, BOD and colour removal. The treatment efficiency of the system at 1.9 g l−1...

Decolorisation of azo dyes during biological effluent treatment can involve both adsorption to cell biomass and degradation by azo-bond reduction during anaerobic digestion. Degradation is expected to form aromatic amines, which may be toxic and recalcitrant to anaerobic treatment but degradable aerobically. Methods for the quantitative detection o...

A simulated textile effluent (STE) was generated for use in laboratory biotreatment studies; this effluent contained one reactive azo dye, PROCION Red H-E7B (1.5 g dm−3); sizing agent, Tissalys 150 (1.9 g dm−3); sodium chloride (1.5 g dm−3) and acetic acid (0.53 g dm−3) together with nutrients and trace elements, giving a mean COD of 3480 mg dm−3....