Search

Pharmaceuticals and personal care products are omnipresent in wastewater world-wide. In order to predict their sorption quantities onto sludge in wastewater treatment plants (WWTPs), the solid–water distribution coefficients (Kd values) of selected pharmaceuticals (antiphlogistics, estrogens, lipid regulators, anti-epileptic and cytostatic agents) and polycyclic musk fragrances (HHCB, AHTN) were determined in primary and secondary sludges taken from a German municipal WWTP. For the Kd determination, batches of primary and secondary sludge slurries were spiked with the respective target compounds and slowly stirred under defined conditions (e.g. an argon atmosphere). Finally, the water and solid sludge phases were analysed. The Kd values of pharmaceuticals ranged from <1 to 500Lkg-1, while those for the polycyclic musk fragrances AHTN and HHCB proved to be up to 5300 and 4900Lkg-1, respectively. The primary and secondary sludge showed significant differences for some pharmaceuticals such as Diclofenac and Cyclophosphamide due to the different pH and composition of the two sludges. The removal rate from the water phase caused by sorption in a WWTP can be reasonably predicted on the basis of the Kd values. [Copyright &y& Elsevier]

The effect of sludge retention time (SRT) and process temperature on the hydrolysis, acidification and methanogenesis of primary sludge was investigated in completely stirred tank reactors (CSTRs). The CSTRs were operated to maintain SRTs of 10, 15, 20 and 30 days at process temperatures of 25°C and 35°C. The rates of hydrolysis and the biodegradability of primary sludge were assessed in batch reactors incubated at 15°C, 25°C and 35°C. The results revealed that the major amount of sludge stabilisation occurred between 0 and 10 days at 35°C and 10 and 15 days at 25°C. Hydrolysis was found to be the rate limiting-step of the overall digestion process, for the reactors operated at 35°C and 25°C, except for the reactor operated at 10 days and 25°C. At the latter conditions, methanogenesis was the rate-limiting step of the overall digestion process. Proteins hydrolysis was limited to a maximum value of 39% at 30 days and 35°C due to proteins availability in the form of biomass. The biodegradability of primary sludge was around 60%, and showed no temperature dependency. The hydrolysis of the main biopolymers and overall particulate COD of the primary sludge digested in CSTRs were well described by first-order kinetics, in case hydrolysis was the rate-limiting step. Similarly, the hydrolysis of the overall particulate COD of the primary sludge digested in batch reactors were described by first-order kinetics and revealed strong temperature dependency, which follows Arrhenius equation. [Copyright &y& Elsevier]

Anaerobic digestion is an appropriate technique for the treatment of sludge before final disposal and it is employed worldwide as the oldest and most important process for sludge stabilization. In general, mesophilic anaerobic digestion of sewage sludge is more widely used compared to thermophilic digestion. Furthermore, thermal pre-treatment is suitable for the improvement of stabilization, enhancement of dewatering of the sludge, reduction of the numbers of pathogens and could be realized at relatively low cost especially at low temperatures. The present study investigates (a) the differences between mesophilic and thermophilic anaerobic digestion of sludge and (b) the effect of the pre-treatment at 70°C on mesophilic and thermophilic anaerobic digestion of primary and secondary sludge. The pre-treatment step showed very positive effect on the methane potential and production rate upon subsequent thermophilic digestion of primary sludge. The methane production rate was mostly influenced by the pre-treatment of secondary sludge followed by mesophilic and thermophilic digestion whereas the methane potential only was positively influenced when mesophilic digestion followed. Our results suggest that the selection of the pre-treatment duration as well as the temperature of the subsequent anaerobic step for sludge stabilization should depend on the ratio of primary to secondary sludge. [Copyright &y& Elsevier]

The role of the pH in the anaerobic digestion of domestic primary sludge at mesophilic temperature was evaluated. Since solubilization of organic materials is seriously affected by pH, much research has been performed for the evaluation of significant pH influence on the production of soluble organic carbon in the acid phase. In this study, the performance of continuously stirred anaerobic reactors for the production of soluble chemical oxygen demand (SCOD) and volatile fatty acids (VFAs) in domestic primary sludge was investigated. In the first anaerobic reactor, the pH was not controlled (pH-uncontrolled) whereas the pH was fixed at 6.5 (pH-controlled) in the second reactor. Two sets were performed. Results of both sets indicated that, VSS was removed with a corresponding production of VFAs and SCOD in both reactors. However, production of VFAs and SCOD stopped earlier in the pH-controlled reactors. Methanogenic phase started to operate at earlier times whereas hydrolysis and fermentation were still operating in the pH-uncontrolled reactors. The process stability and efficiency of anaerobic digestion of substrates such as domestic primary sludge can be improved by anaerobic digestion elutriated phased treatment (ADEPT) in which the acid elutriation reactor and methanogenic reactor are separated. In this respect, ADEPT was introduced. [ABSTRACT FROM AUTHOR]

This investigation was undertaken with the aim of developing a new wastewater prefermentator reactor in order to increase the percentages of sedimentation, hydrolysis and prefermentation of all the organic matter present in the raw wastewater, using only one unit of pre-treatment. The study was carried out using a pilot fixed bed biofilm reactor of 43.3 L in net volume. HRT of 0.5, 1, 2 and 4 h were applied. The reactor has been operating for 403 days during which it has been fed on raw wastewater from the city of Santander, in Spain. The results showed that it is possible to carry out the sedimentation and prefermentation of the organic matter contained in the raw wastewater in this reactor. The TSS average elimination percentage was higher than 50% during the whole testing period. The highest percentage of TSS retained in the reactor was 70% with a HRT of 4 hours and a flow rate of 0.3 m/h. The maximum CODTotal elimination percentage was 30% for any of the four OL tried. The CODParticulate average solubility was greater than 40%. About 44% of the CODDissolved in the effluent consisted of VFA. The highest concentration of VFA measured in the effluent was 44 mg COD/L, applying a HRT of 1 h. The average acidising was slightly higher than 30%. The acetic, propionic, butyric and valeric acids were the species of VFA detected, the acetic acid being the one present in a larger amount (>50%). The production rate of VFA increases as the HRT decreases. [ABSTRACT FROM AUTHOR]

The effect of pH on anaerobic solubilization of domestic primary sludge and activated sludge was investigated and compared. Anaerobic solubilization was carried out in continuously stirred anaerobic reactors at mesophilic temperature (35°C) and pH was fixed at 6.5 (pH-controlled). Many researches reported the serious effects of pH on the solubilization of organic materials. Thus, the aim of pH control in the reactors consisting of domestic primary and activated sludges, was the evaluation of retardation in hydrolysis/acidogenesis at low pH values. Since primary and activated sludges have different biodegradation characteristics, results were compared. Results indicated that the destruction of Total Suspended Solids (TSS) and Volatile Suspended Solids (VSS) were better in the pH-controlled reactors. In both sludges, acetic acid was the main Volatile Fatty Acid (VFA) produced. In the pH-controlled reactors, VSS reduction was found to be 72% in about 20 days in the anaerobic digestion of activated sludge, whereas for the same interval VSS reduction could only be achieved by 32% in primary sludge at 35°C. When primary sludge was used as substrate, the pH-uncontrolled and the pH-controlled reactors removed VSS with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD). However, production of VFAs and SCOD was ceased after 5 days in the pH-controlled reactor whereas VFAs and SCOD production continued after 5 days in the pH-uncontrolled reactor, which indicated that hydrolysis and fermentation did not complete and continued longer. On the other hand; in either the pH-uncontrolled or the pH-controlled reactor of activated sludge, VSS was not removed with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD). It was apparent that solubilization was occurring, however this solubilization was not observed as VFA production. When total methane production and total COD (CODtot) removal were estimated using VSS removal in both types of sludges, results indicated that pH control enhanced biogas productions as well as CODtot removals. [ABSTRACT FROM AUTHOR]

A methodology to reduce the phosphorus content of biosolids produced by enhanced biological phosphorus removal treatment plants was studied. The process consists of mixing phosphate-rich waste activated sludge (WAS) with either primary sludge or the supernatant from a primary-sludge gravity thickener under anaerobic conditions to induce the release of phosphate from WAS. The solubilized phosphate could then be chemically sequestered and removed from the biosolids. Bench-scale phosphate release experiments were conducted with sludge from the Nine Springs Wastewater Treatment Plant (Madison, Wisconsin) at different mixing ratios. A WAS/primary sludge or WAS/supematant mixing ratio of 1:1 (by volume) resulted in the highest phosphate release in the batch tests. For experiments with less than 50% WAS (by volume), the total phosphate release was directly proportional to the amount of WAS added. When the mixture contained more than 50% WAS, total phosphate release was limited by the volatile fatty acids (VFAs) available. For the Nine Springs plant, optimal biosolids phosphorus could be achieved using a primary sludge/WAS mixing ratio of 1.02 kg volatile suspended solids (VSS)/kg VSS or a supernatant VFA/WAS mixing ratio of 0.02$ kg VFA/kg VSS. The expected reduction in phosphorus content would be 35 and 32% if primary sludge or supernatant, respectively, were used. Water Environ. Res., 75, 254 (2003). [ABSTRACT FROM AUTHOR]

Carbon source production from primary sludge in wastewater treatment plants (WWTPs) via anaerobic fermentation process has been paid more attention. However, slow hydrolysis rate and low yield of short-chain fatty acids (SCFAs) limited its application. This study aimed at improving the anaerobic fermentation efficiency of primary sludge by alkali regulation (NaOH, Na 2 CO 3 and Ca(OH) 2), and revealing the mechanism. Results showed that three kinds of alkalis allowed enhancing hydrolysis and acidification, and reducing methane production in the anaerobic fermentation process of primary sludge. The Na 2 CO 3 regulation contributed to highest yield and productivity of SCFAs, reaching 1626 mg COD/L and 0.189 g COD/g VSS at 4th day, respectively. Microbial community structure analysis indicated that the relative abundance of fermentative microbial community was improved in the alkali regulation system, where methanogenic archaea was effectively inhibited. The continuous flow experiment further verified that the Na 2 CO 3 regulation could steadily increase yield of SCFAs in the anaerobic fermentation process of primary sludge, and the yield was also the highest among three kinds of alkali regulation. • The yield and productivity of short-chain fatty acids were improved by alkali regulation. • Alkali regulation promoted both chemical and microbial hydrolysis of primary sludge. • The methanogenic archaea was inhibited by adding the degree of alkalinity. • The Na 2 CO 3 regulation enabled the highest productivity of short-chain fatty acids. [ABSTRACT FROM AUTHOR]

It's not clear how fermentation affects the succession and interspecific interaction of functional microorganism in primary sludge anaerobic fermentation system. So as to explore the decisive role of temperature on microorganisms to reveal the mechanism, four fermentation experiments groups (25, 35, 45, and 55 °C) were designed. Results indicated the promotion in proportion of acetic and iso-valeric acid with temperature increasing. High-throughput sequencing reflected that the dominant microbial groups in all samples were Proteobacteria, Firmicutes, Bacteroidetes, Synergetes, Spirochaetae, and then key microbial interspecific interaction changed significantly due to the adjustment of microbial temperature. In addition, amino acid metabolism was the lowest at 35 °C, but carbohydrate metabolism was the highest. The metabolic abundances of amino acids at different temperatures were the highest, but the differences among kind of amino acids were significant. This study could reveal the effect of temperature on VFAs production in terms of microbial interspecific interaction and lay a theoretical foundation for sludge fermentation. [Display omitted] 1. High temperature did not significantly promote the formation of VFAs. 2. The highest richness and diversity appeared at 45 °C group. 3. Interspecific interaction changed significantly with the adjustment of temperature. 4. Temperature did not change the dominance of carbohydrate metabolism. [ABSTRACT FROM AUTHOR]

We assessed the relationship between municipality COVID-19 case rates and SARS-CoV-2 concentrations in the primary sludge of corresponding wastewater treatment facilities. Over 1700 daily primary sludge samples were collected from six wastewater treatment facilities with catchments serving 18 cities and towns in the State of Connecticut, USA. Samples were analyzed for SARS-CoV-2 RNA concentrations during a 10 month time period that overlapped with October 2020 and winter/spring 2021 COVID-19 outbreaks in each municipality. We fit lagged regression models to estimate reported case rates in the six municipalities from SARS-CoV-2 RNA concentrations collected daily from corresponding wastewater treatment facilities. Results demonstrate the ability of SARS-CoV-2 RNA concentrations in primary sludge to estimate COVID-19 reported case rates across treatment facilities and wastewater catchments, with coverage probabilities ranging from 0.94 to 0.96. Lags of 0 to 1 days resulted in the greatest predictive power for the model. Leave-one-out cross validation suggests that the model can be broadly applied to wastewater catchments that range in more than one order of magnitude in population served. The close relationship between case rates and SARS-CoV-2 concentrations demonstrates the utility of using primary sludge samples for monitoring COVID-19 outbreak dynamics. Estimating case rates from wastewater data can be useful in locations with limited testing availability, testing disparities, or delays in individual COVID-19 testing programs., (© The Author(s) 2022. Published by Oxford University Press on behalf of FEMS.)

Nutrient released from BPR sludge during anaerobic digestion was refixed with Ca2+>>> and Mg2+>>>> ions as calcium phosphate and struvite. The higher contents of Ca and Mg in primary sludge and nightsoil showed potentialities to control the nutrient returning back to liquid stream when these sludges were mixed with BPR sludge. Addition of Mg2+>>>>>>>> to BPR sludge was also effective. The amount of TP removed from a sludge could be computed from the amount of Prefixed by the amount of Ca and Mg removed during digestion. About 40 to 45% of TP and 35 to 39% of TN removal efficiencies could be expected when primary sludge or nightsoil was added to BPR sludge with a volumetric ratio of 0.67/1. With 100mg/L of Mg2+>>>>>>>>>>>>>>>> addition (Ca/Mg molar ratio of 0.81) to BPR sludge, TN and TP removal efficiencies were 52.3% and 58.4%, respectively. [ABSTRACT FROM AUTHOR]

The aim of this study is to improve the management of different types of wastes using an anaerobic digestion process and CH4 production from the semi-continuous co-digestion of multi-substrates of fallen leaves (FL), grass (GR) and primary sludge (PS). As a first step, the co-digestion of FL, GR and PS was carried out using the BMP test based on C/N ratios. The results showed that the best CH 4 production was at a C/N ratio of 13. Kinetic analysis of the methane produced showed no adaptation phase was needed for the methanogenic bacteria to stimulate their anaerobic digestion activity. The inflection point in the cumulative methane production curve is identified as the biological hydrolysis phase of the substrates by endogenous microorganisms. In the second step, semi-continuous co-digestion of FL, GR and PS was carried out. The performance of the reactor was monitored in particular for biodegradability of the feedstock and biogas production rate under different OLRs. The highest biogas production rate of 35 L/d was recorded at an OLR of 1 g VS/L·d. However, partial overloading occurred at an OLR of 1.5 g VS/L·d. The highest CH4 content of biogas produced was achieved at an OLR of 1.0 g VS/L·d. • Semi-continuous co-digestion of multi-substrates of PS, FL, and GR was reported for an optimal methane production. • The highest CMYs and VS removal rate were recorded at C/N ratios of 13 and 16, respectively. • Kinetic analysis of the methane produced was conducted. • The highest biogas production rate and methane content were recorded at an OLR of 1 g VS/L·d. [ABSTRACT FROM AUTHOR]

Resin acids in pulp and paper mills wastewater are potentially partitioned in the solids in post–primary clarification due to higher hydrophobicity with log K ow ∼1.74–5.80. They are known to adversely affect anaerobic digestion (AD) process, although the effect has not been quantified deterministically in control studies. The objective of the present work was to determine the effect of untreated and ozonated spiked resin acids on AD of primary sludge. Batch adsorption tests were conducted to determine the solid-liquid partition coefficient (K d) of resin acids on the primary sludge. Higher K d was obtained at pH 4; however, it was decreased by 78–98% at pH 8. Thereafter, batch AD of model resin acids in primary sludge using food to microorganism ratio (S 0 / X) of 0.5 g t C O D / g V S S indicated only 15–20% removal of resin acids in the liquid phase anaerobically. While, ozonation in pure water using 0.74–1.48 mg O 3 /mg tCOD showed >90% reduction of the test resin acids, an ozone dose of 0.52 mg O 3 /mg tCOD reduced 50–70% spiked resin acids' load to the digester. However, no further removal of resin acids occurred during AD over 30 days. About 42% reduction in methane production compared to the control digestor occurred in the presence of 150 mg/L of resin acids. When treated with 0.52 mg O 3 /mg tCOD, methane production improved and was comparable to the control digestor, indicating that resin acids may not be detrimental to AD at a concentration range of 45–75 mg/L. Image 1 • Resin acids mostly partitioned onto the solids in sludge at pH below pK a. • Anaerobic digestion of resin acids in sludge was only 15–20%. • Methane production was inhibited by resin acids. • Ozone pretreatment of sludge reduced methanogenic inhibition of resin acids. [ABSTRACT FROM AUTHOR]

Commercial carbon source (e.g. methanol) has been frequently used to enhance heterotrophic denitrification for nitrate removal. However, this is not sustainable due to the high cost of chemical purchasing and excessive sludge production. To address these issues, this study reports an integrated denitrification system using primary sludge as solid carbon source. Complete denitrification without any nitrite accumulation achieved at the primary sludge dosage of 6.0 g VSS/g N with the maximum specific nitrate reduction rate of 6.4 mg N/g VSS/h, which was comparable with the reported soluble carbon source. More importantly, as a solid "waste" in municipal wastewater treatment plants (WWTPs), the primary sludge was simultaneously reduced by 65.3%–85.1%, and this avoids the intensive denitrification biomass generation that generally occurs in using the commercial carbon source. Ammonium, phosphate, and recalcitrant organic matter were released meantime. Interestingly, the concentration of ammonium and phosphate declined during the denitrification process. The refractory dissolved organics mainly composed of aromatic protein and microbial by-products. The detailed cycle study suggests that an appropriate denitrification cycle/duration time would largely lower the effluent organics concentration, which can be achieved by monitoring the pH turning point. This study clearly demonstrates that primary sludge is a promising alternative carbon source for biological denitrification with great economic benefits and environmental sustainability. • Denitrification with primary sludge as an alternative carbon source was confirmed. • Released ammonium and phosphate were reduced simultaneously. • PH turning point can be used to determine complete denitrification. • Primary sludge was efficiently utilized with VSS removal of 65.3%–85.1%. • The great economic benefits and environmental sustainability were demonstrated. [ABSTRACT FROM AUTHOR]

The objective of this work was to examine opportunities for reducing the overall cost of lignocellulose hydrolysis to fermentable sugars. Primary sludge (PS), a negative cost lignocellulosic feedstock, was hydrolyzed sludge using a commercial cellulase preparation (Cellic® CTec2) in presence of non-ionic surfactants. Polyethylene glycol (PEG) 4000 facilitated the highest hydrolysis yield of 74.4% which represented a 2-fold increase over the control without surfactant. Response surface methodological analysis at four variables (hydrolysis time, solids, enzyme, and surfactant loadings) revealed that enzymatic hydrolysis was significantly enhanced by the interactive effect of all factors with solids and enzyme loadings as the most significant parameters (p < 0.05). Using ultrafiltration, 40% of the cellulase enzyme was recovered from the enzymatic hydrolysate and reused on fresh PS substrate. The hydrolysate fermentabilty was evaluated in production of 9.7 g/L bioethanol at 92% ethanol yield using Saccharomyces cerevisiae , and in production of 37.8% biolipids by the oleaginous yeast Cutaneotrichosporon oleaginosum at a carbon to nitrogen ratio of 40. The compression load of a sample prepared from the unhydrolyzed PS solids was 102% higher than Portland cement. The potential for valorization of the unhydrolyzed solids as reinforcement material warrants further investigations. • Enzymatic hydrolysis of primary sludge was optimized using statistical methods. • Surfactants increased the enzymatic hydrolysis efficiency and yield. • About a third of the enzyme activity was recovered and recycled. • Enzymatic hydrolysate was evaluated in bioethanol and biolipid production. • Unhydrolyzed solids from sludge hydrolysis was assesses as reinforcement material. [ABSTRACT FROM AUTHOR]

• A thermophilic – mesophilic TPAD was compared with a conventional process. • Values of pH and tVFAs/TA ratio in both TPAD stages were steady for the whole test. • An excellent phase separation between the first and the second reactor was obtained. • The TPAD proved to be more efficient in VS reduction and methane generation. • Only a process of heat recovery made the TPAD system really energy profitable. This study was carried out with the principal aim of obtaining reliable outcomes for the future implementation of a temperature-phased anaerobic digestion (TPAD) process in a large (2 M population equivalent, p.e.) WWTP. With the aid of pilot-scale (10 L) reactors fed by pure primary sludge (PS), a TPAD process, where the first and the second reactor were operated at 50 °C and 38 °C, respectively, was compared with a conventional mesophilic (38 °C) anaerobic digestion (AD) process. The initial hydraulic retention time (HRT) of the first, acidogenic, reactor of the TPAD was reduced from 3 to 2 days in the second part of the test. The results demonstrated that the TPAD system had been stable for all the duration of the test (approx. 100 days), as testified by the steady values of pH and tVFAs/TA ratio, notwithstanding the decrease in the HRT. The TPAD proved to be more efficient in volatile solid (VS) reduction and methane generation, compared to the conventional mesophilic AD process. In fact, the VS reduction increased from 42% to approx. 55% and the specific methane potential (SMP) from 280 to 332 NL/kg VS added. An excellent phase separation was observed between the two acidogenic and methanogenic reactors, as demonstrated by the low SMP (only 3% of the overall production) recorded from the first reactor of the TPAD system. However, the energy analysis demonstrated that the higher SMP obtained in the TPAD was not sufficient to compensate the higher amounts of heat required for sludge heating and heat loss compensation. Only a process of heat recovery could make the TPAD system really profitable, thus increasing the aliquot of energy in the form of methane, available for users external to the WWTP, by 20%. This result represents a step in the evolution of traditional WWTPs towards more energy efficient and sustainable facilities. [ABSTRACT FROM AUTHOR]

Heterotrophic denitrification is a robust and reliable process for nitrogen removal from wastewater. However, wastewater often faces the issue of lacking carbon source. In this study, the feasibility of using primary sludge, a by-product of wastewater treatment plants, to support denitrification of high-strength nitrite wastewater was investigated. Results suggest the desired performance can be achieved with the influent nitrite concentration of 400 to 1200 mg N/L, and the optimal primary sludge dosage for the complete nitrite removal was 3.6 g VSS/g N. Ammonium removal was also detected along with nitrite removal. Microbial analysis reveals various types of denitrifying bacteria and a large number of macromolecular organics degrading bacteria existed in the microbial community. Notably, anammox bacteria, Candidatus Brocadia , was also identified with an abundance of 0.1%. The slow kinetics of carbon source release from primary sludge was likely the reason for the existence of anammox process. This study developed a promising nitrogen removal process using an alternative carbon source for denitrification, and it shows great potential to couple denitrification with anammox to reduce ammonium residue. Unlabelled Image • Primary sludge as solid carbon for denitrification over nitrite was demonstrated. • Complete nitrite removal achieved at primary sludge dosage of 3.6 g VSS/g N • Anammox bacteria was detected with an abundance of 0.1%. • In-situ ammonium removal can be realized via enhanced anammox. [ABSTRACT FROM AUTHOR]

In this study, the fate of several micropollutants (MPs) in wastewater due to coagulation using both fresh and recovered aluminum and iron coagulants was determined. 18 MPs from different groups such as antibiotics, food additives, and surfactants were selected and spiked into the primary influent collected from a local wastewater plant. The distribution of MPs in the recovered coagulant and treated effluent after coagulation was determined for both fresh and recycled coagulants. The distribution of MPs in wastewater and the removal during coagulation were compound specific; MPs with log K ow < 2.5 were predominantly present in the effluent after coagulation, while MPs with log K ow > 2.5 were sorbed on the coagulated sludge. The distribution ratio (K d) of all the MPs (diclofenac, clarithromycin, etc.) with log K ow > 2.5 was determined along with their extent of accumulation in sludge due to the recycling of coagulants. Compounds such as sulfamethoxazole, erythromycin and sulfathiazole, showed low removal during coagulation. The tetracycline group of compounds showed possible chelation with iron and aluminum. Only <10% of the initially spiked MPs with log K ow > 2.5 was being recycled with the recovered coagulant, thus alleviating the concern of accumulation of the MPs during recycle of the coagulants. Image 1 • Effect of coagulation on 18 micropollutants (MPs) in primary sludge was determined. • MPs with log K ow > 2.5 were sorbed on the coagulated sludge. • Recovery of alum and ferric chloride coagulants from coagulated sludge was accomplished. • Reuse of the recovered coagulants did not increase the concentration of MPs in the primary effluent significantly. • Tetracycline group compounds showed possible chelation with the metals in the wastewater matrix. [ABSTRACT FROM AUTHOR]

A two-stage temperature-phased mesophilic anaerobic digestion assay was carried out to study the interaction between various biological pretreatment conditions and the possible synergistic co-digestion of microalgae and primary sludge. The study of growth kinetics of the biochemical methane potential test revealed that a maximum of 36% increase in methane yield was observed from co-digestion of a substrate pretreated by thermophilic aerobic conditions (55 °C and HRT = 2 days) and an 8.3% increase was obtained from the anaerobic pretreated substrate (55 °C and HRT = 3 days). Moreover, no synergistic effects on methane yields were observed in co-digesting the substrate pretreated with high temperature (85 °C). The study also identified specific conditions in which interaction between biological pretreatment and co-digestion might substantially reduce methane yield. Careful optimization of operating conditions, both aerobic and anaerobic pretreatment at moderate thermophilic conditions, can be used as a biological pretreatment to enhance methane yield from the co-digestion of microalgae and primary sludge. [ABSTRACT FROM AUTHOR]

Harvested microalgae Chlorella spp. and primary sludge were co-digested in a laboratory-scale anaerobic membrane bioreactor (AnMBR) under thermophilic conditions (55 °C). The system was run for 700 days divided into four experimental phases to determine the influence of the organic loading rate on the process performance and the microbial community. The rise in organic loading rate from 0.17 to 0.5 gCOD·L−1·d−1 led to a 35% improvement in methane production. The system reached 69% biodegradability working at 0.5 gCOD·L−1·d−1 and a high solids retention time (70 d), indicating the efficient conversion of biomass into biogas through the AnMBR configuration while avoiding possible inhibition by free ammonia. The thermophilic AnMBR provided a stable microbial community dominated by hydrolytic and fermenter members such as Coprothermobacter , Fervidobacterium and Hydrothermae. Syntrophic oxidisers such as W5 were also key in propionate degradation and produced intermediates for later conversion into methane. • 35% improvement in methane production was found tripling the organic loading rate. • 69% biodegradability was reached working at 55 °C and 70 d of solids retention time. • No ammonia inhibition was observed. • Membrane installation and temperature shaped microbial community. • Syntrophic propionate oxidisers were key in anaerobic co-digestion. [ABSTRACT FROM AUTHOR]

• Biochar enhanced high-quality biomethane production from PS. • Biochar accelerated PS hydrolysis and enhanced methane production potential of PS. • Biochar incresed buffering capacity, conductivity and alleviated NH 3 inhibition. • Biochar enhanced sludge reduction and reduced sludge disposal costs. • Biochar could be applied to anaerobic digestion of the mixture of WAS and PS. This study conducted batch and continuous tests to reveal the feasibility of corn stover biochar on improving anaerobic digestion of primary sludge (PS). Dosing biochar (1.82, 2.55 and 3.06 g/g Total Solids (TS)) in digester improved methane content increasing from 67.5% to 81.3–87.3% and enhanced methane production by 8.6–17.8%. Model analysis indicated that biochar accelerated PS hydrolysis and enhanced methane potential of PS. The mechanistic studies showed that biochar enhanced process stability provided by strong buffering capacity and alleviated NH 3 inhibition. In continuous test over 116 days, the volatile solids (VS) destruction in the biochar-dosed digester increased by 14.9%, resulting in a 14% reduction in the volume of digestate for disposal. Biochar changed microbial community in an expected direction for anaerobic digestion. This work suggests that biochar technology would apply to co-digestion of WAS and PS to maximize the energy recovery and sludge reduction from the two sludge streams. [ABSTRACT FROM AUTHOR]

The pulp and paper industry traditionally generates large amounts of wastes at different stages of its production process, such as primary sludge that is extremely wet. The aim of this research is to evaluate a new process methodology aiming the incorporation of primary pulp and paper industry sludge waste, still in its liquid state, into cement and lime-based mortars. This procedure was compared with the incorporation of the waste in its dry state, which results from the traditional beneficiation process based on powder drying. Comparison was performed in terms of technological, durability and environmental performance of both wastes (liquid and dry) incorporated mortars, as well as with reference control mortar without incorporation. Two news models of liquid waste processing, for mortars incorporation, called thin and coarse liquid, were developed in order to evaluate technological parameters such as: consistency, entrained air, water retention, mass density, capillary absorption and mechanical strength. These parameters allow the characterization of durability, life cycle assessment and environmental conditions. Technological properties showed satisfactory results in mortars performance when waste was used as a thin liquid with nominal content (optimal mixture) similar to the reference composition. The air content of the mortar was 12% and the water retention 96.8%. In the hardened state, the optimal mixture had a mass density of 1.76 g/cm3, a capillary coefficient of 20.73 g/dm2.min1/2 and mechanical resistance to compression of 3.7 MPa and to flexion of 1.1 MPa, all results meet the limits of the literature for application in construction. It was found that the beneficiation process, which produces the thin liquid is the most efficient for the incorporation of waste into mortars when compared to the dry method. Indeed, the thin liquid waste incorporated mortars showed improved technological, durability and environmental properties. • Development of a new methodology for beneficiation of waste from paper industry. • Two liquid incorporation procedure were evaluated (thin and a coarse liquid). • The thin liquid (TL) presented the best technological and environmental properties. • The thin liquid (TL) can be used in mortars for civil construction. [ABSTRACT FROM AUTHOR]

• Anaerobic co-digestion of primary sludge and microalgae enhances methane production. • 73% of biodegradability was achieved from co-digestion through a mesophilic AnMBR. • A robust microbial community was observed. • Chloroflexi and Proteobacteria were the most abundant phyla. • Syntrophic groups along with Methanosaeta were key in methane production. Anaerobic co-digestion of primary sludge and raw microalgae (Scenedesmus and Chlorella) was performed in a lab-scale semi-continuous anaerobic membrane bioreactor to assess the biological performance and identify the microbial community involved in the co-digestion process. The reactor was operated at 35 °C for 440 days, working at a solids retention time of 100 days. The system achieved 73% biodegradability and showed high stability in terms of pH and volatile fatty acids. An enriched microbial community was observed. Of the several phyla, Chloroflexi and Proteobacteria were the most abundant. Cellulose-degraders phyla (Bacteroidetes, Chloroflexi and Thermotogae) were detected. Syntrophic microorganisms played an important role in intermediate degradation, enhancing methane production, mainly carried out by Methanosaeta. A nutrient-rich effluent (400 mg NH 4 -N·L−1 and 29 mg PO 4 -P·L−1) and digestate (860 mg N·L−1 and 151 mg P·L−1) were obtained. The bio-nutrients released from anaerobic co-digestion could be reused for microalgae cultivation or agricultural applications. [ABSTRACT FROM AUTHOR]