Mesophilic and thermophilic temperature co-phase anaerobic digestion compared with single-stage mesophilic- and thermophilic digestion of sewage sludge

The performance of thermophilic and mesophilic temperature co-phase anaerobic digestions for sewage sludge, using the exchange process of the digesting sludge between spatially separated mesophilic and thermophilic digesters, was examined, and compared to single-stage mesophilic and thermophilic anaerobic digestions. The reduction of volatile solids from the temperature co-phase anaerobic digestion system was dependent on the sludge exchange rate, but was 50.7-58.8%, which was much higher than 46.8% of single-stage thermophilic digestion, as well as 43.5% of the mesophilic digestion. The specific methane yield was 424-468 mL CH(4) per gram volatile solids removed, which was as good as that of single-stage mesophilic anaerobic digestion. The process stability and the effluent quality in terms of volatile fatty acids and soluble chemical oxygen demand of the temperature co-phase anaerobic digestion system were considerably better than those of the single-stage mesophilic anaerobic processes. The destruction of total coliform in the temperature co-phase system was 98.5-99.6%, which was similar to the single-stage thermophilic digestion. The higher performances on the volatile solid and pathogen reduction, and stable operation of the temperature co-phase anaerobic system might be attributable to the well-functioned thermophilic digester, sharing nutrients and intermediates for anaerobic microorganisms, and selection of higher substrate affinity anaerobic microorganisms in the co-phase system, as a result of the sludge exchange between the mesophilic and thermophilic digesters.     

Mesophilic and thermophilic anaerobic digestion of faecal sludge in a pilot plant digester

In many developing countries, the sewage consisting of faecal sludge is discharged untreated into rivers, lakes and coastal areas. This poses a health hazard and a risk to the ecosystem, and wastes a resource which could produce sustainable energy. This paper reports results from an anaerobic digester of 1000L used for digestion of faecal waste at mesophilic and thermophilic conditions. The specific biogas production rate from faecal sludge was in the range of 0.06–0.12 m³/(kg DM.d) at mesophilic conditions at NTP (Normal Temperature & Pressure i.e. 25 °C and 1 atm. Pressure) and 0.1–0.21 m³/(kg DM.d) at thermophilic conditions calculated at NTP. The number of toilet users affects the biogas production with changes in the organic loading rate. The results showed 97% reductionin chemical oxygen demand and 90% reduction in biological oxygen demand of anaerobic digester discharge water as compared to inlet substrate values.     

Evaluation of continuous mesophilic, thermophilic and temperature phased anaerobic digestion of microwaved activated sludge

The effects of microwave (MW) pretreatment, staging and digestion temperature on anaerobic digestion were investigated in a setup of ten reactors. A mesophilic reactor was used as a control. Its performance was compared to single-stage mesophilic and thermophilic reactors treating pretreated and non-pretreated sludge, temperature-phased (TPAD) thermophilic-mesophilic reactors treating pretreated and non-pretreated sludge and thermophilic-thermophilic reactors also treating pretreated and non-pretreated sludge. Four different sludge retention times (SRTs) (20, 15, 10 and 5 d) were tested for all reactors. Two-stage thermo-thermo reactors treating pretreated sludge produced more biogas than all other reactors and removed more volatile solids. Maximum volatile solids (VS) removal was 53.1% at an SRT of 15 d and maximum biogas increase relative to control was 106% at the shortest SRT tested. Both the maximum VS removal and biogas relative increase were measured for a system with thermophilic acidogenic reactor and thermophilic methanogenic reactor. All the two-stage systems treating microwaved sludge produced sludge free of pathogen indicator bacteria, at all tested conditions even at a total system SRT of only 5 d. MW pretreatment and staging reactors allowed the application of very short SRT (5 d) with no significant decrease in performance in terms of VS removal in comparison with the control reactor. MW pretreatment caused the solubilization of organic material in sludge but also allowed more extensive hydrolysis of organic material in downstream reactors. The association of MW pretreatment and thermophilic operation improves dewaterability of digested sludge.     

Fate of organotins in sewage sludge during anaerobic digestion

Adsorption onto sewage sludge is an important process for the elimination of tributyltin (TBT) from wastewater. However as the disposal of sewage sludge to agricultural land is a significant route for recycling biosolids, there exists an issue as to whether the potential long-term build-up of organotins in agricultural soil is acceptable, from a human health and environmental point of view. For the sustainable use of biosolids in agriculture it is essential to control and reduce the quantities of persistent pollutants such as organotins in sewage sludge. In this study, a sampling program was designed to establish the levels of TBT (and other organotins) in sewage sludge and their reduction during anaerobic treatment and processing prior to disposal. Experiments were also undertaken to assess the fate of TBT in laboratory scale anaerobic digesters where the influence of digester operating parameters could be evaluated. Organotin concentrations were determined using capillary gas chromatography with flame photometric detection. The results demonstrated that the majority of TBT remained concentrated in the solid phase (sewage sludge). Concentrations of TBT in sewage sludge were approximately 18 mg kg(-1) (dry weight) and both laboratory experiments and fieldwork demonstrated that degradation of TBT during anaerobic digestion of sludge was minimal.     

Kinetics of inactivation of indicator pathogens during thermophilic anaerobic digestion

Thermophilic anaerobic sludge digestion is a promising process to divert waste to beneficial use, but an important question is the required temperature and holding time to achieve a given degree of pathogen inactivation. In this study, the kinetics of inactivation of Ascaris suum and vaccine strain poliovirus type 1 (PVS-1), selected as indicators for helminth ova and enteric viruses respectively, were determined during anaerobic digestion at temperatures ranging from 51 to 56 °C. Inactivation of both indicator organisms was fast with greater than two log reductions achieved within 2 h for A. suum and three log reductions for PVS-1, suggesting that the current U.S. regulations are largely conservative. The first-order inactivation rate constants k followed Arrhenius relationship with activation energies of 105 and 39 KJ mol^?1 for A. suum and PVS-1, respectively indicating that A. suum was more sensitive to temperature. Although inactivation was fast, the presence of compounds in the sludge that are known to be protective of pathogen inactivation was observed, suggesting that composition-dependent time–temperature relationships are necessary.     

Aerobic waste activated sludge (WAS) for start-up seed of mesophilic and thermophilic anaerobic digestion

Since there are very limited numbers of thermophilic anaerobic digesters being operated, it is often difficult to start up a new one using sludge from an existing reactor as a seed. However, for obvious reasons it seems few attempts have been made to compare the start-up performance of thermophilic anaerobic digestion using different sources of seed sludges. The purpose of this study was to evaluate the start-up performance of anaerobic digestion using aerobic waste activated sludge (WAS) from a plant which has no anaerobic digesters and mesophilic anaerobic digested sludge (ADS) as the seed source at both mesophilic (35 degrees C) and thermophilic (55 degrees C) temperatures. In this study, two experiments were conducted. First, thermophilic anaerobic reactors were seeded with WAS (VSS = 4400 mg/L) and ADS (VSS = 14,500 mg/L) to investigate start-up performance with a feed of acetate as well as propionate. The results show that WAS started to produce CH4 soon after acetate feeding without a lag time, while ADS had a lag time of 10 days. When the feed was changed to propionate, WAS removed propionate down to below the detection limit of 10 mg/L, while ADS removed little propionate and produced little CH4. Second, in order to further compare the methanogenic activity of WAS and ADS, both mesophilic and thermophilic reactors were operated. WAS acclimated to anaerobic conditions shortly (< 5 days at both mesophilic and thermophilic) and after acclimating it produced more CH4 per unit amount of seeded VSS than ADS. WAS at mesophilic temperature biodegraded acetate at the same rate as for thermophilic. However WAS at mesophilic temperature biodegraded propionate at a much faster rate than at thermophilic. WAS as the seed source of anaerobic digestion resulted in much better performance than ADS at both mesophilic and thermophilic temperatures for both acetate and propionate metabolism.     

The effects of temperature, pH, and ammonia concentration on the inactivation of Ascaris eggs in sewage sludge

The reported inactivation of Ascaris eggs during alkaline sludge stabilization is highly variable. The objective of our research was to better understand the sources of this variability by quantifying the effects of temperature, pH, and ammonia concentration on the inactivation of indigenous Ascaris eggs in wastewater sludge. Primary sludge was supplemented with ammonia (0, 1000, and 5000mg/l NH(3)-N) and Ca(OH)(2) and incubated in sealed bottles across the range of temperatures (20, 30, 40, and 50 degrees C) and pH (7 and 12) that may be encountered during treatment. Changes in egg viability over time were fit to a two-parameter kinetic model (shoulder and first-order region); to compare treatment conditions, the time for 99% inactivation (t(99)) was also calculated. Each 10 degrees C increase in temperature caused a significant decrease in t(99) at every pH and ammonia concentration tested. At 50 degrees C, the effect of temperature was dominant, such that no effect of pH or ammonia was observed. At 30 and 40 degrees C, raising the pH from 7 to 12 decreased t(99), but at 20 degrees C no pH effect was seen over 80 d (very little inactivation occurred). At 20, 30, and 40 degrees C, the addition of ammonia dramatically decreased t(99). The effect of pH could not be completely separated from that of ammonia, as the unamended sludge samples contained 100-200mg/l indigenous ammonia. Because temperature, pH, and ammonia all contributed to Ascaris egg inactivation, it is essential that these parameters are measured and accounted for when assessing the effectiveness of alkaline stabilization. Furthermore, inactivation by ammonia could be exploited to improve the effectiveness of alkaline sludge stabilization.     

Performance improvement and decolourization in the high-solid thermophilic anaerobic digestion of thermally pretreated sewage sludge

This laboratory-scale study attempted performance improvement and decolourization in the high-solid thermophilic anaerobic digestion of thermally pretreated sewage sludge, as it tends to be disturbed by ammonia inhibition and colour generation. Sewage sludge was adjusted to 7%–8% total solids (TS), and pretreated at 150°C for 1 h. The digesters were operated at 55°C and 20 days hydraulic retention time. An addition of powdered activated carbon (approximately 2% of the feed TS) significantly contributed to the removal of propionate and reduced the colour in digested sludge by about 27%. Microbial analysis detected less abundance of bacterial Synergistia and archaeal Methanosarcina and implied more hydrogenotrophic methanogenesis with the activated carbon addition. Conditioning with ferric chloride for dewatering digested sludge mitigated the colour of dewatered liquor by about 67%. Therefore, these methods were demonstrated to be effective and partly overcome the above-mentioned problems.     

Strategies for changing temperature from mesophilic to thermophilic conditions in anaerobic CSTR reactors treating sewage sludge

Thermophilic anaerobic digestion presents an advantageous way for stabilization of sludge from wastewater treatment plants. Two different strategies for changing operational process temperature from mesophilic (37 degrees C) to thermophilic (55 degrees C) were tested using two continuous flow stirred tank reactors operated at constant organic loading rate of 1.38 g VS/l reactor/day and hydraulic retention time of 20 days. In reactor A, the temperature was increased step-wise: 37 degrees C-->42 degrees C-->47 degrees C-->51 degrees C-->55 degrees C. While in reactor B, the temperature was changed in one-step, from 37 degrees C to the desired temperature of 55 degrees C, The results showed that the overall adaptation of the process for the step-wise temperature increment took 70 days in total and a new change was applied when the process was stabilized as indicated by stable methane production and low volatile fatty acids concentrations. Although the one-step temperature increase caused a severe disturbance in all the process parameters, the system reached a new stable operation after only 30 days indicating that this strategy is the best in changing from mesophilic to thermophilic operation in anaerobic digestion plants.     

The mesophilic and thermophilic anaerobic digestion of coffee waste containing coffee grounds

The anaerobic digestion of waste water containing significant levels of coffee grounds was assessed in mesophilic and thermophilic batch studies and CSTRs fed daily. A 58% reduction in VS was seen in both batch studies. Proximate compositional analysis showed that the waste had a high lipid component (26–33%). Levels of lipid, hemicellulose, α-cellulose and lignin were determined before and after digestion. These components were reduced as follows: lipid by 87% in the mesophilic study and 65% in the thermophilic study, α-cellulose by 51% in both mesophilic and thermophilic batch studies, hemicellulose by 22% in the mesophilic studies and 64% in the thermophilic studies. The lignin component was not reduced in either study. Mesophilic continuous digestion was achieved at a loading rate of 1.3 kg COD m⁻³ day⁻¹ (25 day HRT) for 99 days. Addition of sodium bicarbonate alone was not sufficient for long term anaerobic digestion. Addition of Ca(OH)₂, nitrogen, phosphorus and trace elements, however, gave successful digestion with COD and VS removal of 60% and a gas production rate of 0.34 11⁻¹ day⁻¹ (65–70% methane). Low levels of TVFA and high levels of bicarbonate alkalinity were present. Thermophilic digestion could be established at 1.6 kg COD m⁻³ day⁻¹ (20 day HRT) with the addition of sodium bicarbonate alone, or Ca(OH)₂ with nitrogen, phosphorus and trace elements. However long term digestion could not be established beyond 50 days without a increase in TVFA occurring.     

The behaviour of nitrilotriacetic acid during the anaerobic digestion of sewage sludge

In laboratory simulations of the anaerobic sludge digestion process, the impact of the detergent builder nitrilotriacetic acid (NTA) on digester efficiency has been studied. It was concluded that NTA at concentrations up to 30 mg l⁻¹ had no adverse effect on anaerobic digestion. However, analysis of the digested sludge indicated that only 29–45% of the influent NTA was removed during treatment. To differentiate between biological and physical processes of removal, biological activity in the digesters was arrested by the addition of sodium azide. Effluent NTA concentration did not increase indicating that biological activity was not responsible for the removal observed.Batch experiments undertaken to evaluate NTA solubility in digested sludge (containing azide) at two solids concentrations indicated a decrease in soluble NTA with increasing solids concentration.It is concluded that the removal of NTA observed during anaerobic digestion was not biological and in part was the result of adsorption onto the solid phase.     

Laboratory studies of virus survival during aerobic and anaerobic digestion of sewage sludge

The survival of three enteroviruses (polio 1, coxsackie B3 and echo 1) and a rotavirus (SA-11) was studied under laboratory conditions. The effects of temperature, dissolved oxygen, detention time, sludge source and virus type on virus inactivation were determined. Temperature was the single most important factor influencing the rate of virus inactivation. No significant differences were found for virus inactivation rates at dissolved oxygen levels between 0.9 and 5.8 mg/l. However, the inactivation rate of the viruses under aerobic conditions was found to be significantly greater than the inactivation rate under anaerobic conditions (−0.77log₁₀/day vs −0.33 log₁₀/day). Sludge source, detention time and virus type did not significantly influence the rate of virus inactivation.     

Effect of microwave hydrolysis on transformation of steroidal hormones during anaerobic digestion of municipal sludge cake

Fate and removal of 16 steroidal (estrogenic, androgenic and progestogenic) hormones were studied during advanced anaerobic digestion of sludge cake using microwave (MW) pretreatment. Effect of pretreatment temperature (80, 120, 160 °C), operating temperature (mesophilic at 35 ± 2 °C, thermophilic at 55 ± 2 °C) and sludge retention time (SRT: 20, 10, 5 days) were studied employing eight lab-scale semi-continuously fed digesters. To determine the potential effect of MW hydrolysis, hormones were quantified in total (sorbed + soluble) and supernatant (soluble) phases of the digester influent and effluent streams. Seven of 16 hormones were above the method reporting limit (RL) in one or more of the samples. Hormone concentrations in total phase of un-pretreated (control) and pretreated digester feeds ranged in <157–2491 ng/L and <157–749 ng/L, respectively. The three studied factors were found to be statistically significant (95% confidence level) in removal of one or more hormones from soluble and/or total phase. MW hydrolysis of the influent resulted in both release (from sludge matrix) and attenuation of hormones in the soluble phase. Accumulation of estrone (E1) as well as progesterone (Pr) and androstenedione (Ad) in most of the digesters indicated possible microbial transformations among the hormones. Compared to controls, all pretreated digesters had lower total hormone concentrations in their influent streams. At 20 days SRT, highest total removal (E1+E2+Ad +Pr) was observed for the thermophilic control digester (56%), followed by pretreated mesophilic digesters at 120 °C and 160 °C with around 48% efficiency. In terms of conventional performance parameters, relative (to control) improvements of MW pretreated digesters at a 5-d SRT ranged in 98–163% and 57–121%, for volatile solids removal and methane production, respectively.     

Psychrophilic and mesophilic anaerobic digestion of brewery effluent: a comparative study

Two expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactors (3.38 l active volume) were used to directly compare psychrophilic (15 degrees C), anaerobic digestion (PAD) to mesophilic (37 degrees C) anaerobic digestion (MAD) for the treatment of a brewery wastewater (chemical oxygen demand (COD) concentration of 3,136+/-891 mg l(-1)). Bioreactor performance was evaluated by COD removal efficiency and biogas yields at a range of hydraulic and organic loading rates. Specific methanogenic activity (SMA) assays were also employed to investigate the activity of the biomass in the bioreactors. No significant difference in the COD removal efficiencies (which ranged from 85-93%) were recorded between PAD and MAD during the 194-d trial at maximum organic and hydraulic loading rates of 4.47 kg m(-3) day(-1) and 1.33 m(3) m(-3) day(-1), respectively. In addition, the methane content (%) of the biogas was very similar. The volumetric biogas yield from the PAD bioreactor was approximately 50% of that from the MAD bioreactor at an organic loading rate of 4.47 kg COD m(-3) day(-3) and an applied liquid up-flow velocity (V(up)) of 2.5 m h(-1). Increasing the V(up) in the PAD bioreactor to 5 m h(-1) resulted in a volumetric biogas production rate of approximately 4.1 l d(-1) and a methane yield of 0.28 l CH(4) g(-1) COD d(-1), which were very similar to the MAD bioreactor. Significant and negligible biomass washout was observed in the mesophilic and psychrophilic systems, respectively, thus increasing the sludge loading rate applied to the former and underlining the robustness of the latter, which appeared underloaded. A psychrotolerant mesophilic, but not truly psychrophilic, biomass developed in the PAD bioreactor biomass, with comparable maximum SMA values to the MAD bioreactor biomass. PAD, therefore, was shown to be favourably comparable to MAD for brewery wastewater treatment and biogas generation.     

Modeling volatile organic sulfur compounds in mesophilic and thermophilic anaerobic digestion of methionine

Processes involved in volatile organic sulfur compound (VOSC) generation and degradation in mesophilic and thermophilic digestion of methionine were identified, kinetically studied and a mathematical model was established. MM was found to be the only VOSC directly generated from methionine degradation. MM was methylated to form DMS and both MM and DMS were subsequently degraded to H2S. Mixed-second order kinetics were found to best fit the VOSC generation and conversion processes. The kinetic constants (average values) for MM generation and methylation and MM and DMS degradation were estimated to be 0.0032, 0.0047, 0.027, and 0.013 l g⁻¹ h⁻¹ respectively at 35 °C and 0.0069, 0.0012, 0.0083, 0.005 l g⁻¹ h⁻¹ respectively at 55 °C. More rapid MM release and slower VOSC decline at thermophilic temperature implied that VOSC could be more problematic at thermophilic temperatures as compared to mesophilic conditions.     

Comparative process stability and efficiency of anaerobic digestion; mesophilic vs. thermophilic

The comparative process stability and efficiency of mesophilic (35 degrees C) and thermophilic anaerobic digestion (55 degrees C) has been evaluated for four different reactor configurations, which are: daily batch-fed single-stage continuously stirred tank reactor (CSTR), continuously fed single-stage CSTR, daily batch-fed two-phase CSTR, and daily batch-fed non-mixed single-stage reactor. The results are discussed for three periods: (1) start-up, (2) steady state, and (3) organic loading rate (OLR) increase until reactor failure (pH below 5.5). During the start-up, the single-stage CSTRs at both temperatures showed the least stability, while the non-mixed single-stage reactors reached steady state in the shortest time with relatively stable pH and low volatile fatty acid (VFA). In the case of the thermophilic non-mixed reactor, efficient removal of propionate occurred but supplementation of nutrients (Ca, Fe, Ni, and Co) was required when VFA increased. The results imply the importance of inorganic nutrients bioavailability. The comparative results of the reactor performance at steady state clearly showed the superior performance of the thermophilic non-mixed reactor with respect to lower VFA, higher gas production and volatile solids removal implying that microbial consortia proximity can alleviate the problem of poor effluent quality in thermophilic system. During the OLR increase until reactor failure, all thermophilic reactors except the thermophilic non-mixed reactor showed increases in propionate concentrations as the OLR increased, while all mesophilic reactors except the mesophilic two-phase system showed little increase in VFA concentrations. When all reactors had the same conditions with OLR increase, the continuously fed reactors showed the lowest gas production, while the non-mixed reactors showed the highest gas production at both temperatures. It is hypothesized that the non-mixing reactor configuration has closer microbial consortia proximity than others. Therefore, the results in this study indicated the importance of microbial consortia proximity. A proposed model for the effect of the distance between two syntrophic bacteria reasonably matched the data in this study.     

The behaviour of nitrilotriacetic acid during the anaerobic digestion of co-settled sewage sludge

The removal of nitrilotriacetic acid (NTA) in four laboratory scale anaerobic digesters treating mixed primary sludge has been investigated. Two digesters received mixed primary sludge containing 30% waste activated sludge whilst the remaining two received 15% waste activated sludge. Nitrilotriacetic acid was added at concentrations between 10 and 30 mg l⁻¹. Digesters which received waste activated sludge previously aerobically acclimatised to NTA removed NTA after periods of adaptation between 4 and 16 days.A memory effect was observed over periods of up to 30 days. It was concluded that the mechanism of NTA removal was biological. The type of organism responsible for NTA removal, and the possible impact of NTA on sludge treatment, sludge disposal and the receiving environment is discussed.     

Extracellular biological organic matters in sewage sludge during mesophilic digestion at reduced hydraulic retention time

To operate an anaerobic digester at low hydraulic retention time (HRT) is welcome in practice. This study characterized the extracellular biological organic matter (EBOM) and supernatant organics for a sewage sludge digested in a lab-scale mesophilic digester (5 l) running at an HRT of 20, 15 or 10 d. The hydrophilic and hydrophobic acid fractions were the principal components in the sludge EBOM. The hydrolysis rates for hydrophobic acid fraction related EBOM at 10 d HRT and that of hydrophilic fraction related proteins in supernatant at 20 d HRT limited the anaerobic processes. Improved hydrolysis of soluble hydrophilic fraction assisted improving digester performance at 20 d HRT. To shorten digestion HRT, efficiency of hydrophobic acid fraction hydrolysis has to be practiced.     

Evaluation of continuous mesophilic anaerobic sludge digestion after high temperature microwave pretreatment

Effect of microwave pretreatment (MW) high temperature (175 °C) and MW intensity to waste activated sludge digested with acclimatized inoculum in single- and dual-stage semi-continuous mesophilic anaerobic digesters at different sludge retention times (SRTs) (20, 10 and 5 days) were investigated. MW pretreatment led to similar sludge stabilization at low SRTs (5 and 10 days). Although lowering MW intensity slightly improved sludge solubilization, it had a negative effect on digestion at low SRTs. Single-stage digesters with MW pretreatment surpass dual-stage digesters performances.     

Drivers of microbial community composition in mesophilic and thermophilic temperature-phased anaerobic digestion pre-treatment reactors

Temperature-phased anaerobic digestion (TPAD) is an emerging technology that facilitates improved performance and pathogen destruction in anaerobic sewage sludge digestion by optimising conditions for 1) hydrolytic and acidogenic organisms in a first-stage/pre-treatment reactor and then 2) methogenic populations in a second stage reactor. Pre-treatment reactors are typically operated at 55–65 °C and as such select for thermophilic bacterial communities. However, details of key microbial populations in hydrolytic communities and links to functionality are very limited. In this study, experimental thermophilic pre-treatment (TP) and control mesophilic pre-treatment (MP) reactors were operated as first-stages of TPAD systems treating activated sludge for 340 days. The TP system was operated sequentially at 50, 60 and 65 °C, while the MP rector was held at 35 °C for the entire period. The composition of microbial communities associated with the MP and TP pre-treatment reactors was characterised weekly using terminal-restriction fragment length polymorphism (T-RFLP) supported by clone library sequencing of 16S rRNA gene amplicons. The outcomes of this approach were confirmed using 454 pyrosequencing of gene amplicons and fluorescence in-situ hybridisation (FISH). TP associated bacterial communities were dominated by populations affiliated to the Firmicutes, Thermotogae, Proteobacteria and Chloroflexi. In particular there was a progression from Thermotogae to Lutispora and Coprothermobacter and diversity decreased as temperature and hydrolysis performance increased. While change in the composition of TP associated bacterial communities was attributable to temperature, that of MP associated bacterial communities was related to the composition of the incoming feed. This study determined processes driving the dynamics of key microbial populations that are correlated with an enhanced hydrolytic functionality of the TPAD system.