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J.A. Pavez Jara

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4 records found

Accumulating ammoniacal nitrogen instead of melanoidins determines the anaerobic digestibility of thermally hydrolyzed waste activated sludge

Journal article - J.A. Pavez Jara, J.B. van Lier, M.K. de Kreuk

Full-scale thermal hydrolysis processes (THP) showed an increase in nutrients release and formation of melanoidins, which are considered to negatively impact methanogenesis during mesophilic anaerobic digestion (AD). In this research, fractionation of THP-sludge was performed to elucidate the distribution of nutrients and the formed melanoidins over the liquid and solid sludge matrix. Degradation of the different fractions in subsequent AD was assessed, and the results were compared with non-pre-treated waste activated sludge (WAS). Results showed that the THP-formed soluble melanoidins were partially biodegradable under AD, especially the fraction with molecular weight under 1.1 kDa, which was related to protein-like substances. The use of THP in WAS increased the non-biodegradable soluble chemical oxygen demand (sCOD) after AD, from 1.1% to 4.9% of the total COD. The total ammoniacal nitrogen (TAN) concentration only slightly increased during THP without AD. However, after AD, TAN released was 34% higher in the THP-treated WAS compared to non-treated WAS, i.e., 36.7 ± 0.7 compared to 27.4 ± 0.4 mgTANreleased/gCODsubstrate, respectively. Results from modified specific methanogenic activities (mSMAs) tests showed that the organics solubilised during THP, were not inhibitory for acetotrophic methanogens. However, after AD of THP-treated sludge and WAS, the mSMA showed that all analysed samples presented strong inhibition on methanogenesis due to the presence of TAN and associated free ammonia nitrogen (FAN). In specific methanogenic activities (SMAs) tests with incremental concentration of TAN/FAN and melanoidins, TAN/FAN induced strong inhibition on methanogens, halving the SMA at around 2.5 gTAN/L and 100 mgFAN/L. Conversely, melanoidins did not show inhibition on the methanogens. Our present results revealed that when applying THP-AD in full-scale, the increase in TAN/FAN remarkably had a greater impact on AD than the formation of melanoidins.@en

Effects of thermal hydrolysis process-generated melanoidins on partial nitritation/anammox in full-scale installations treating waste activated sludge

Journal article - J.A. Pavez Jara, J.B. van Lier, M.K. de Kreuk

Thermal hydrolysis process (THP) is a well-established anaerobic digestion (AD) pre-treatment technology. Despite the THP benefits the pre-treatment increases the concentrations of nutrients and melanoidins in the digestate reject water after dewatering. The increased concentrations of nutrients and melanoidins formed during THP-AD can impact downstream processes, such as struvite precipitation and partial nitritation/anammox (PN/A). In our present work, six full-scale PN/A influents and effluents were sampled in The Netherlands (4 with THP and 2 without THP). Full-scale samples were characterised and the stoichiometric O2 consumption and melanoidins chelated to trace elements were analysed. The results showed that THP increased the concentration of total ammoniacal nitrogen (TAN), chemical oxygen demand (COD), total organic carbon (TOC), UVA 254 and colour, which are indicators of melanoidins occurrence. THP furthermore decreased the stoichiometric NO3−-N production from the PN/A reaction in effluents. The disparity between stoichiometric and measured NO3− -N in the THP-using plants was explained by the proliferation of denitrifiers. Moreover, denitrification improved the N removal efficiency due to the consumption of the stoichiometrically-produced NO3− -N. Also, the stoichiometric O2 consumption increased in the plants using THP, reaching up to 56% of the O2 used for partial oxidation of TAN. Trace elements analysis revealed that the plants with elevated concentrations of melanoidins in the effluent showed a high percentage of chelated multivalent cations, particularly transition metals such as Fe. Kendall correlation coefficient analysis showed that the chelation of multivalent cations was correlated mainly with colour occurrence in the reject waters. Overall, the results indicated that in PN/A systems using THP-AD increased O2 consumption and trace elements availability should be considered during the process design.@en

Role of the composition of humic substances formed during thermal hydrolysis process on struvite precipitation in reject water from anaerobic digestion

Journal article - J.A. Pavez Jara, W.P. Iswarani, W.P. Iswarani, W.P. Iswarani, J.B. van Lier, M.K. de Kreuk

Thermal hydrolysis process (THP) is a widely used pre-treatment method in the anaerobic digestion (AD) of waste municipal sewage sludge. A post AD dewatering step of the digestate produces a liquid stream called reject water. THP increases the concentration of humic substances (H ...

Nutrients release and melanoidins formation during thermal hydrolysis of waste activated sludge and implications in downstream processes

Doctoral thesis - J.A. Pavez Jara

This thesis research investigated the dynamics of nutrient release and the formation of melanoidins during thermal hydrolysis processes (THP) of waste activated sludge (WAS) preceding mesophilic anaerobic digestion (AD). In Chapter 2, a fractionation of THP-sludge allowed for researching the distribution of nutrients and melanoidins over the liquid and solid fraction of the sludge matrix during AD. The soluble melanoidins formed during THP were found to be partially biodegradable during subsequent AD, particularly those with a molecular weight under 1.1 kDa, associated with protein-like substances. In addition, total ammoniacal nitrogen (TAN) concentrations exhibited a modest increase during THP, but a substantial increase was observed during AD, negatively impacting acetotrophic methanogenesis. In Chapter 3, the influence of THP on PO43--P release and precipitation during AD is described. The dynamics in soluble PO43--P concentrations were most pronounced in WAS from enhanced biological phosphorus removal (EBPR) plants. The results indicated an increment in TAN and PO43--P release with THP temperature, while varying soluble concentrations were observed during AD. Full-scale samples provided insights into the precipitation of multivalent cations with PO43--P. The results showed that precipitation reactions during AD governed the concentration of soluble nutrients during THP-AD. In this thesis, also the impact of THP on downstream processes was researched, particularly reject water treatment after AD. The research focused on the potential consequences of elevated concentrations of humic substances (HSs) and nutrients in the reject water from digestate dewatering. In Chapter 4, research is described on the effects of THP pre-treatment on the struvite precipitation efficiency, considering the chemical characteristics of HSs. Batch experiments revealed the influence of melanoidins and humic acids on struvite precipitation at different pH levels. The intrinsic characteristics of HSs emerged as critical factors affecting struvite yield, morphology, and colour of the formed precipitates. In Chapter 5, six full-scale partial nitritation and anammox (PN/A) influents and effluents were sampled, with four wastewater treatment plants (WWTPs) using THP and two without. Characterization of the samples revealed that THP increased concentrations of TAN, and aromatic organics, which is an indication of melanoidins occurrence. Additionally, THP decreased stoichiometric NO3--N concentrations in effluents from the PN/A reactors. This study also emphasizes the importance of considering increased O2 consumption and possible limited trace element availability during PN/A process operation, when utilizing THP-AD to optimize overall system performance. In summary, the results of this thesis provide an understanding of the interactions and consequences of THP in full-scale scenarios, focusing on the dynamics in nutrient release and the effects of melanoidins formation, in THP, AD, and downstream processes for nutrient removal (PN/A and struvite precipitation).@en

Contributed

6 records found

Hydrochar from Fischer-Topsch biosludge

Is there an application for Fischer-Tropsch biosludge hydrochar produced via hydrothermal carbonization

Master thesis - L.D. van der Loos, W. de Jong, M.K. de Kreuk, L. Cutz, J.A. Pavez Jara, Georg Stockinger, R.E.F. Lindeboom

Improving circularity and reducing greenhouse gas emissions can be achieved by utilizing secondary streams like Fischer-Tropsch biosludge, which is typically disposed of in landfills. Biochar, which has accumulated increased interest recently, has significant potential for decrea ...

Recalcitrant compounds from thermally hydrolysed sewage sludge

Master thesis - Z. WANG, M.K. de Kreuk, W. de Jong, J.A. Pavez Jara, Jan Pels, Rian Visser

Thermal hydrolysis (TH) has been widely applied to sewage sludge treatment to improve downstream anaerobic digestion (AD) by enhancing organic solids hydrolysis and subsequent biogas productivity. However, TH also has several drawbacks, including the formation of recalcitrant compounds, which are anaerobically non-biodegradable and even inhibitory to the downstream AD. Melanoidins produced from the Maillard reaction have been regarded as a representative of such compounds. Theoretically, the production of melanoidins increases with increasing TH temperature. This study collaborated with TORWASH®, a patented TH technology developed by TNO, aiming to characterise the recalcitrant compounds derived under TORWASH® conditions from 180 - 210 °C. In addition, we investigated the effects of anaerobic pre-digestion on the TH performance, attempting to increase the biogas productivity of digestate. Moreover, we also sought pretreatment methods that could mitigate the production of recalcitrant compounds. By reviewing the studies of Zhang et al. (2020) and other researchers in this field, we found that acidic pretreatments could be the solution. Then, we assumed that the addition of acetic acid and CO2 gas could limit the progression of the Maillard reaction. A laboratory simulation of the TH process was performed on waste activated sludge (WAS) at 180 - 200 °C and anaerobically pre-digested WAS at 180 - 210 °C. The following TH tests with acidic pretreatments were only conducted on WAS at 190 °C. We found that the production of recalcitrant compounds (soluble humic substances) increased with increasing reaction temperature, corresponding to increased UVA254 and colour formation. Proteins were primarily hydrolysed or denatured during TH, and competition for carbohydrates between the Maillard and caramelisation reactions could occur at 190 °C and above. In addition, TH disintegrated high molecular weight DOM > 1 kDa into low molecular weight DOM < 0.1 kDa, and stronger sludge disintegration occurred at higher reaction temperatures. Moreover, BMP decreased after anaerobic pre-digestion but increased after TH treatment. The liquid fraction of pre-digested WAS could reach an equivalent degree of anaerobic biodegradability as that of WAS when applying a higher reaction temperature. All acidic pretreatments applied decreased the production of soluble humic substances by 10 %, corresponding to a 13 % decrease in UVA254. CO2 pressurisation at 10 bar could effectively reduce the formation of fulvic-acid like and humic-acid like matter, compared with the untreated sample. The effect of 20 bar CO2 was less pronounced than that of 10 bar CO2, whether or not the samples were pre-added with HAc.

Evaluation of compounds generated in the thermal hydrolysis process on microbial activities in partial nitritation/anammox process

Master thesis - J. Lou, M.K. de Kreuk, J.B. van Lier, T.J. Heimovaara, J.A. Pavez Jara

Anaerobic digestion (AD) is a traditional technique to treat sewage sludge and produce biogas. Thermal hydrolysis process (THP) is a feasible pretreatment for AD by improving the biodegrdability of organic compounds. Partial nitritation/anammox (PN/A) process could be applied in ...

Influence of humic substances created in THP on partial nitritation step of PN/A reactors

Master thesis - S. Wang, M.K. de Kreuk, Mark C.M. van Loosdrecht, J.A. Pavez Jara

Anaerobic digestion (AD) is an effective and economical in secondary sludge management. Thermal hydrolysis process (THP) is a reliable pre-treatment method to improve the biodegradability of sludge. Partial nitritation and anammox process (PN/A) is a suitable method used to remove nitrogen in reject water which has a low COD/N ratio. However, some organic compounds produced in THP process, such as melanoidins, have negative effects on AOO and anammox bacteria. Considering that humic substances occupy a large part of the soluble organics in reject water of THP-AD process. Therefore, this study aimed to investigate the acute and long-term toxicity of three types of humic substances (commercial humic acid, melanoidins and reject water) on partial nitritation step of PN/A process. The biodegradability of three types of humic substances under aerobic and anaerobic conditions, and the evolution of humic substances during the biodegradability assays were also analysed. The results showed that all three types of humic substances had higher biodegradability under aerobic condition than that under aerobic condition, and melanoidins had more biodegradable compounds than reject water and humic acid. During the AD process, humic substances acted as electron acceptors, decreasing the cumulative methane production of all three types of humic substances compared to the blank. Also, small MW fractions were transformed to large MW fractions in all three types of humic substances during both aerobic and anaerobic digestion. Moreover, during aerobic and AD, both fulvic acid-like and humic acid-like substances were formed. In addition, the results of acute toxicity tests showed commercial humic acids had a stronger inhibitory effect than reject water and melanoidins on AOO biomass. In addition, a positive correlation between humic substances concentration and AOO activity loss was observed. The long-term operation of PN reactor was failed due to the formation of granular sludge in the reactor and the growth of AOO biomass in the tubing and culture medium.

Effects of thermal hydrolysis process (THP) on struvite crystallisation from reject water of anaerobically digested sludge

Master thesis - W.P. Widya Prihesti Iswarani, M.K. de Kreuk, J.B. van Lier, A.E.D.M. van der Heijden, J.A. Pavez Jara

Various technologies have been implemented in wastewater treatment plants (WWTPs) to generate clean effluent with minimised impacts on the environment. Thermal hydrolysis process (THP) and struvite crystallisation reactors are two examples of these technologies. THP generates humic-like substances, known as melanoidins, that are presumed to disrupt struvite crystallisation. THP also solubilises trace elements that are prone to complex with melanoidins. On the one hand, the trace elements might stay bound to the melanoidins in the supernatant or on the other hand; they might be present in struvite as impurities. As both THP and struvite crystallisation are promising technologies, the objective of this study was to understand the effects of THP on struvite crystallisation. Results showed that melanoidins generated by THP affected P removal and the amount of produced struvite in struvite crystallisation at pH 6.5 and 7.25, but not at pH 8. In contrary to melanoidins, humic acids (HA) were found to reduce P removal efficiency at pH 8. Melanoidins resulted in slightly higher N-NH4 concentration in the supernatant in all pH values. Melanoidins and HA also changed crystal colour from white into brown and black, respectively. Furthermore, melanoidins and HA changed the morphology of struvite crystals from X-shaped and long rod-like crystals into square-shaped crystals and at the same time reduced the diameter of struvite crystal. Regardless, melanoidins did not change the Mg:N-NH4:P-PO4 molar ratio. Melanoidins did not significantly influence induction time, except at pH 7.25 and 2 g TOC/L melanoidins. In addition to this, melanoidins were found to form complexes with magnesium which subsequently decreased the supersaturation and affected struvite crystallisation. Different elements had different fate on struvite crystallisation. Melanoidins formed complexes with Mn and Ni, resulting in a higher concentration in the supernatant compared to the condition without melanoidins. Based on PHREEQC modelling, humic substances (HS) formed complexes with Ca, Cu, and Fe. Certain trace elements (Ca, Co, Cu, Fe, and Mn) and heavy metals (Al and Cr) were found to co-precipitate with struvite in all experimental conditions; meanwhile, Se minerals only co-precipitated at pH 8. All minerals showed decreasing SI with increasing HS concentrations. The decrease of SI implied that there would be less co-precipitation of Al, Ca, Co, Cr, Cu, Fe, Mn, and Se in struvite crystals. Nevertheless, their presence in the supernatant would not guarantee the bioavailability of the trace elements for bacteria in partial nitritation/anammox (PN/A) processes due to the chance of complexation with HS. Eventually, it could be concluded that THP affected struvite crystallisation and Response Surface Methodology (RSM) confirmed that the optimum conditions for struvite crystallisation with maximised N and P contents and big diameter were pH of 7.9 and 0 g TOC/L melanoidins. Nonetheless, melanoidins prevented co-precipitation of trace elements in struvite crystals.

Effect of Melanoidins and Metals on Hydrolysis in Anaerobic Digestion

Master thesis - S.J. Sutaria, M.K. de Kreuk, J.B. van Lier, R. Kleerebezem, J.A. Pavez Jara

Sludge management has gained importance over the years due to high sludge treatment and disposal cost, stringent disposal laws, and a need to move towards sustainable energy production. Anaerobic Digestion (AD) of waste activated sludge (WAS) is a favoured sludge stabilisation technique due to its low energy footprint. Hydrolysis – the first step in AD is often the rate-limiting step and thus pre-treatment such as Thermal Hydrolysis Process (THP) are implemented before AD to improve the biodegradability of WAS and biogas production. However, THP leads to the formation of recalcitrant compounds such as melanoidins which are presumed to have a similar effect as Humic substances on AD. Also, THP leads to the release of metals incorporated in sludge flocs by the degradation of extracellular polymeric substances (EPS) structures. Therefore, this study aimed to understand the effect of melanoidins and metals on the hydrolysis step in AD. The interaction between melanoidins and cations Fe2+, Ca2+, Mg2+, Cu2+, K+, and NH4+ was studied using ultra-filtration and ICP-MS. The effect of these melanoidins-metals interactions on enzymatic hydrolysis of cellulose and proteins was investigated using fluorescence essay and Response Surface Methodology (RSM) modeling. The mechanism of inhibition of hydrolysis by melanoidins and metal was investigated using SEC-HPLC. The results showed that complexation of melanoidins with metals shows the trend - Fe2+ > Ca2+ > Mg2+ > Cu2+ > K+ ≥ NH4+. The ions with higher charge and ionic radius interacted with melanoidins more effectively. The melanoidins-metal interaction increased with an increase in melanoidins concentration most likely due to more phenolic and carboxylic functional groups available for binding. Fe3+ leads to an increase in molecular weight (MW) of melanoidins due to inter-molecular interaction caused by complete charge neutralisation, while no MW changes are observed with Cu2+ and Ca2+. Individually, melanoidins decreased, Fe3+ increased, while Cu2+ decreased the rate of hydrolysis of cellulose. In the presence of melanoidins, the inhibiting effect of Cu2+ is decreased with increasing melanoidins concentration. Similarly, the positive effect of Fe3+ is decreased with increasing melanoidins concentration. Protein hydrolysis was completely inhibited with 3 mM metals concentration. Melanoidins and Fe3+ concentrations had no major impact on protein hydrolysis while Cu2+ inhibits hydrolysis even at 0.15 mM concentration. Therefore, it was hypothesised that Cu2+ causes enzymatic inhibition, but in the presence of melanoidins, melanoidins-Cu2+ complexes formation mitigates the toxic effect of Cu2+ on hydrolysis thus improving the rate of hydrolysis. While, Fe3+ improved hydrolysis by facilitating substrate-enzyme interaction but in presence of melanoidins, melanoidins-Fe3+ complexation leads to the non-availability of Fe3+ to facilitate hydrolysis process thus having no major impact on the rate of hydrolysis.