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[Display omitted] • The role of GAC addition and voltage application in thermophilic AD was examined. • GAC addition enhanced biogas production and decreased dissolved COD and VFAs. • PFAS sorption amplified by more C atoms and sulfonated headgroup presence. • Moderate removal (35–61%) for 4 out of 6 PFAS in bioreactors with GAC. • Increase of Acinetobacter suggest its pivotal role in PFAS biotransformation. Limited information is available on the removal of per- and polyfluoroalkyl substances (PFAS) in anaerobic digestion (AD). Τhe fate of six PFAS was studied in thermophilic bioreactors in the presence of granular activated carbon (GAC) and voltage application. Reactors with GAC exhibited lower concentrations of volatile fatty acids and higher methane production compared to those with and without the application of voltage. Analysis of PFAS in dissolved and solid phase showed that their distribution was dependent on perfluorocarbon chain length and functional group. Mass balances showed that PFAS were not removed during conventional AD or after applying voltage; however, significant removal (up to 61 ± 8 %) was observed in bioreactors with GAC for perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorooctane sulfonate (PFOS). Biomass characterization showed that in these bioreactors, the relative abundance of Acinetobacter and Pseudomonas was higher, indicating their potential role in PFAS biotransformation. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) can be used to break down sludge structure and generate carbonaceous hydrochar suitable for solid fuel or value-added material applications. The separation of char and the reaction medium however generates a filtrate, which needs to treated before potential discharge. Thus, this work determined filtrate properties based on HTC temperature and sludge moisture content and estimated the discharge emissions and the potential increase in analyte loads to an industrial wastewater treatment plant based on derived regression models. Direct discharge of HTC filtrate would significantly increase effluent emissions at the mill, indicating the filtrate treatment is crucial for the future implementation of HTC at pulp and paper mills. Recycling the HTC filtrate to the wastewater plant would lead to only a nominal increase in effluent flow, but would increase the suspended solids, BOD, COD and total nitrogen loads by 0.1–0.8%, 3.8–5.3%, 2.7–3.1% and 42–67%, respectively, depending on HTC temperature. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the feasibility of medical stone (MS) on microbial biomass, bacteria genes copy numbers, mitigation of gaseous emissions and its correlation with analyzed parameters during the biosolids composting. Composting of the biosolids by amendment of MS 0%, 2%, 4%, 6% and 10% (on dry weight basis) was performed using a 130-L composting reactor. The results showed that with increasing the dosage of MS, the CH 4 , N 2 O and NH 3 emission were reduced by 60.5–88.3%, 46.6–82.4% and 38.2–78.5%, respectively. In addition, the 6–10% MS amendment enhanced the organic waste mineralization and prolonged the thermophilic phase. The abundance of ammonia oxidizing bacteria (AOB) and archaea (AOAB) were decreased during the first 28 days, but considerable increment was observed during the maturation phase which indicated that AOB and AOAB were liable for nitrification during the curing phase of composting. A significant correlation was observed among the all analyzed parameters in 6–10% MS blended treatments. [ABSTRACT FROM AUTHOR]

The objective of this study was to identify the effect of mixture of additives to improve the enzymatic activities, organic matter humification and diminished the bioavailability of heavy metals (HMs) during biosolids co-composting. In this study, zeolite (Z) (10%, 15% and 30%) with 1%lime (L) (dry weight basis of biosolids) was blended into the mixture of biosolids and wheat straw, respectively. The without any amendment and 1%lime applied treatments were run for comparison (Control). The Z + L addition resulted rapid organic matter degradation and humification with maximum enzymatic activities. In addition, higher dosage of Z + 1%L amendment reduced the bioavailability of HMs (Cu and Zn) and improved the end product quality as compared to control and 1%L applied treatments. However, the 30%Z + 1%L applied treatment showed maximum humification and low bioavailability of HMs but considering the economic feasibility and compost quality results, the treatment with 10%Z + 1%L is recommended for biosolids co-composting. [ABSTRACT FROM AUTHOR]

Limitations on current wastewater treatment plant (WWTP) biological processes and solids disposal options present opportunities to implement novel technologies that convert WWTPs into resource recovery facilities. This review considered replacing or augmenting extensive dewatering, anaerobic digestion, and off-site disposal with new thermo-chemical and liquid extraction processes. These technologies may better recover energy and metals while inactivating pathogens and destroying organic pollutants. Because limited direct comparisons between different sludge types exist in the literature for hydrothermal liquefaction, this study augments the findings with experimental data. These experiments demonstrated 50% reduction in sludge mass, with 30% of liquefaction products converted to bio-oil and most metals sequestered within a small mass of solid bio-char residue. Finally, each technology’s contribution to the three sustainability pillars is investigated. Although limiting hazardous materials reintroduction to the environment may increase economic cost of sludge treatment, it is balanced by cleaner environment and valuable resource benefits for society . [ABSTRACT FROM AUTHOR]

Mixed sludge from a pulp and paper mill was hydrothermally carbonized at 180–260 °C for 0.5–5 h with the use of HCl or NaOH for determining the effect of acid and base additions during sludge carbonization. Based on the results carbonization was mainly governed by dehydration, depolymerization and decarboxylation of sludge components. Additive type had a statistically significant effect on hydrochar carbon content and carbon and energy yield, of which especially energy yield increased through the use of HCl. The theoretical energy efficiencies of carbonization increased with decreasing reaction temperature, retention time and the use of HCl and suggested that the energy requirement could be covered by the energy content of attained hydrochar. The BOD 5 /COD-ratios of analyzed liquid samples indicated that the dissolved organic components could be treated by conventional biological methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • A carbon-neutral and sustainable blue-green algae biochar (BGBC) was prepared. • BGBC activated sodium sulfite (SS) with significant 4-NP removal from sludge matrices. • The contributions of oxidizing species and functional groups to SS activation were evaluated. • SS increased Denitratisoma abundance, a key microbe that degrades 4-NP in WAS. 4-Nonylphenol is a typical endocrine-disrupting compound found in waste-activated sludge. This study evaluates the feasibility of blue-green algae (Spirulina platensis)-based biochar as a carbon-neutral material to improve sodium sulfite (S(IV))-mediated sludge purification. Blue-green algae-based biochar is an effective activator (at 500 °C and 3 × 10−6 M) of sodium sulfite and removed 75 % of 4-nonylphenol at pH 6 using at 1.7 g/L of dosage. Possible synergistic relationships among the coexisting oxidizing species (SO 3 •−, SO 4 •−, HO•, and 1O 2), obvious defect structure, and abundant carbonyl oxygen groups on the surface of the biochar together dived advanced oxidation process. The bacterial consortia promoted the decomposition of biologically available substrates in the biosolid mixture, which led to the enrichment of Denitratisoma, and boosted 4-nonylphenol biodegradation. This study outlines a potential carbon–neutral, cost-effective, and sustainable sludge treatment strategy using renewable blue-green algae-based biochar, aiding 4-nonylphenol biodegradation in waste-activated sludge. [ABSTRACT FROM AUTHOR]

This work studied the feasibility of co-gasification of biosolids with biomass as a means of disposal with energy recovery. The kinetics study at 800 °C showed that biomass, such as switchgrass, could catalyze the reactions because switchgrass ash contained a high proportion of potassium, an excellent catalyst for gasification. However, biosolids could also inhibit gasification due to interaction between biomass alkali/alkaline earth metals and biosolids clay minerals. In the pilot scale experiments, increasing the proportion of biosolids in the feedstock affected gasification performance negatively. Syngas yield and char conversion decreased from 1.38 to 0.47 m 3 /kg and 82–36% respectively as the biosolids proportion in the fuel increased from 0% to 100%. Over the same range, the tar content increased from 10.3 to 200 g/m 3 , while the ammonia concentration increased from 1660 to 19,200 ppmv. No more than 25% biosolids in the fuel feed is recommended to maintain a reasonable gasification. [ABSTRACT FROM AUTHOR]

Aerobic digestion batch tests were run on a sludge model that contained only two fractions, the heterotrophic biomass (XH) and its endogenous residue (XP). The objective was to describe the stabilization of the sludge and estimate the endogenous decay parameters. Modeling was performed with Aquasim, based on long-term data of volatile suspended solids and chemical oxygen demand (VSS, COD). Sensitivity analyses were carried out to determine the conditions for unique identifiability of the parameters. Importantly, it was found that the COD/VSS ratio of the endogenous residues (1.06) was significantly lower than for the active biomass fraction (1.48). The decay rate constant of the studied sludge (low bH, 0.025 d-1) was one-tenth that usually observed (0.2 d-1), which has two main practical significances. Digestion time required is much more long; also the oxygen uptake rate might be <1.5 mgO2/gTSS h (biosolids standards), without there being significant decline in the biomass. [ABSTRACT FROM AUTHOR]

Anaerobic membrane bioreactors (AnMBRs) enhance carbon neutrality with biomethane recovery from wastewater; however, microbial signaling, which may affect biological performances, was poorly understood. Here, we thus evaluate quorum sensing (QS) dynamics while monitoring acyl-homoserine lactones (AHLs) and autoinducer-2 (AI-2) levels during long-term AnMBR operations after sludge inoculation. Significant organic removal and methane production were achieved with the reactor startup. Signal molecule levels varied with transient organic loading rates, depending on their types. A starving condition may cause an increase in short- and medium-chain AHLs and AI-2. Biopolymers, biosolids, volatile fatty acids, and alkalinity levels had positive correlations with short- and medium-chain AHLs and AI-2, whereas methane production had positive correlations with long-chain AHLs. The principal component analysis of QS signal composition and biological performance data explains their interconnectivity. The findings of this study help to understand that QS signals regulate metabolic pathways in addition to microbial group behaviors., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Abstract: A laboratory-scale staged anaerobic fluidized membrane bioreactor (SAF-MBR) system was used to treat a municipal wastewater primary-clarifier effluent. It was operated continuously for 192days at 6–11L/m2/h flux and trans-membrane pressure generally of 0.1bar or less with no fouling control except the scouring effect of the fluidized granular activated carbon on membrane surfaces. With a total hydraulic retention time of 2.3h at 25°C, the average effluent chemical oxygen demand and biochemical oxygen demand concentrations of 25 and 7mg/L yielded corresponding removals of 84% and 92%, respectively. Also, near complete removal of suspended solids was obtained. Biosolids production, representing 5% of the COD removed, equaled 0.049g VSS/g BOD5 removed, far less than the case with comparable aerobic processes. The electrical energy required for the operation of the SAF-MBR system, 0.047kWh/m3, could be more than satisfied by using the methane produced. [Copyright &y& Elsevier]

Abstract: This study compared the effect of four pure carbon supplements on biological denitrification to a liquor derived as a by-product from the wet oxidation (WO) of waste activated sludge. Sequencing batch reactors were used to acclimate sludge biomass, which was used in batch assays. Acetate, WO liquor and ethanol-supplementation generated the fastest denitrification rates. Acetate and WO liquor were efficiently utilised by all acclimated biomass types, while poor rates were achieved with methanol and formate. When comparing an inoculum from an ethanol-supplemented and non-supplemented wastewater treatment plant (WWTP), the ethanol-acclimated sludge obtained superior denitrification rates when supplemented with ethanol. Similarly high nitrate removal rates were achieved with both sludge types with acetate and WO liquor supplementation, indicating that WO liquors could achieve excellent rates of nitrate removal. The performance of the WO liquor was attributed to the variety of organic carbon substrates (particularly acetic acid) present within the liquor. [Copyright &y& Elsevier]

Abstract: 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 benefits and level of acid required. Pretreatment to pH 2 was concluded to be the most effective. In batch digestion this yielded the same biogas after 13days as compared to untreated WAS at 21days digestion. In semi-continuous digestion experiments (12day hydraulic retention time at 35°C) it resulted in a 14.3% increase in methane yield compared to untreated WAS, also Salmonella was eradicated in the digestate. Dewatering investigations suggested that the acid pretreated WAS required 40% less cationic polymer addition to achieve the same cake solid content. A cost analysis was also carried out. [Copyright &y& Elsevier]

Abstract: This study elucidates the co-composting of biosolids and spent activated clay (SAC) using physio-chemical, bioassay, and spectroscopic methods. A pilot-scale pile of blended limed biosolids, SAC, and rice husk was composted for 15weeks. The changes in temperature, pH, Fourier-transform infrared (FT-IR) spectra, C/N, and germination index (GI) of Chinese cabbage (Brassica chinensis) seeds with time support the goal of producing a mature compost with a decline in the SAC acidity of associated with biosolids. Cadmium, Cr, Cu, Ni, and Pb in the initial biosolids were converted from labile fractions into relatively immobile phases upon maturation. Temperature, moisture, pH, C/N, and GI were used to separate the composting process into three phases – initial, thermophilic, and cooling, based on a score plot of principal component analysis (PCA). The values of the parameters of interest reveal that the compost fulfills the requirements of compost maturity in the literature. [Copyright &y& Elsevier]

Abstract: The ability of three composted materials to immobilize cadmium (Cd) was examined in order to assess their potential for recovering soils contaminated with this metal. Composted pine bark (PB) pH 5.6, spent mushroom compost (SM) pH 8.0, and composted pruning waste+biosolids (BS) pH 6.9 (containing 81%, 75% and 47% total organic matter, respectively) were characterized. FT-IR and CP-MAS 13C NMR spectroscopy indicated the BS and SM to have a higher percentage of aliphatic and carboxyl groups than PB. The composts were artificially contaminated with Cd (80 and 200mgkg−1) and, after 4 weeks incubation, subjected to sequential extraction. In column leaching experiments, the total Cd leached from the composts exposed to both Cd treatments was similar, but much less leached from the BS (0.2%) than the PB (4.0%) or SM (0.7%). The greater capacity of BS to immobilize Cd was attributed to the greater humification of its organic matter and higher content of inorganic components, particularly Fe. [Copyright &y& Elsevier]

Abstract: The aim of this study was to evaluate the performance of thermophilic sludge digestion at decreasing sludge retention time (SRT) and increasing organic loading rate (OLR), in terms of methane production, effluent stabilisation, hygienisation and dewaterability. Focus was put on determining indicators to help prevent process failure. To this end, a lab-scale reactor was operated for nearly 2 years at 55°C. Methane production rate was increased (from 0.2 to 0.4–0.6 d−1) by decreasing the SRT from 30 to 15–10days, while increasing the OLR from 0.5 to 2.5–3.5kgVS d−1. Sludge dewaterability was worsened at SRT below 15days; while pathogen destruction was always successful. The following concentrations might be used to prevent process failure: VFA C2–C5 (3.7gCODL−1), acetate (0.6gL−1), acetate/propionate (0.5), intermediate alkalinity (1.8gCaCO3 L−1), intermediate/partial alkalinity (0.9), intermediate/total alkalinity (0.5), CH4 in biogas (55%). [Copyright &y& Elsevier]

Abstract: Sludge management has become a key issue in wastewater treatment, representing some 20–60% of the operational costs of conventional wastewater treatment plants. The high water content of the sludge results in large daily flow rates to be handled and treated. Thus, the search for methods to improve sludge volume reduction continues to be of major interest. The technology known as sludge treatment wetlands has been used for sludge dewatering since the late 1980s. Major advantages include its low energy requirements, reduced operating and maintenance costs, and a reasonable integration in the environment. However, the number of plants in operation is still low in comparison with conventional technologies. This study represents a review of the state of the art of sludge treatment wetlands. The main characteristics and operational aspects of the technology are described, including a summary of the main results reported in the literature. Finally, the efficiency of sludge treatment wetlands versus conventional treatments is compared. [Copyright &y& Elsevier]

Abstract: This study examined the hydrolysis of lignocellulose extracted from municipal wastewater treatment process residuals for the purpose of investigating low-cost feedstocks for ethanol production, while providing an alternative solid waste management strategy. Primary and thickened waste activated sludges and anaerobically digested biosolids underwent various pre-treatments to enhance subsequent enzymatic hydrolysis. Half of the pre-treated samples were dried and grinded, while the other half were used as is (wet). The wet primary sludge yielded the highest reducing sugar conversions. When wet primary sludge without pre-treatment was hydrolyzed at 40°C and an enzyme loading of 800U/g substrate, 31.1±2.7% was converted to reducing sugars in 24h. This increased to 54.2±4.0% when HCl and KOH pre-treatments were applied. FTIR analyses were used to examine differences in the sludge compositions. These indicated that the cellulose content in the primary sludge was higher than that of the thickened waste activated sludge and biosolids, which was consistent with the higher reducing sugar yields observed in the primary sludge. [Copyright &y& Elsevier]

Optimization of sludge management can help reducing sludge handling costs in wastewater treatment plants. Sludge drying reed beds appear as a new and alternative technology which has low energy requirements, reduced operating and maintenance costs, and causes little environmental impact. The objective of this work was to evaluate the efficiency of three full-scale drying reed beds in terms of sludge dewatering, stabilization and hygienisation. Samples of influent sludge and sludge accumulated in the reed beds were analysed for pH, Electrical Conductivity, Total Solids (TS), Volatile Solids (VS), Chemical Oxygen Demand, Biochemical Oxygen Demand, nutrients (Total Kjeldahl Nitrogen (TKN) and Total Phosphorus (TP)), heavy metals and faecal bacteria indicators (Escherichia coli and Salmonella spp.). Lixiviate samples were also collected. There was a systematic increase in the TS concentration from 1–3% in the influent to 20–30% in the beds, which fits in the range obtained with conventional dewatering technologies. Progressive organic matter removal and sludge stabilization in the beds was also observed (VS concentration decreased from 52–67% TS in the influent to 31–49% TS in the beds). Concentration of nutrients of the sludge accumulated in the beds was quite low (TKN 2–7% TS and TP 0.04–0.7% TS), and heavy metals remained below law threshold concentrations. Salmonella spp. was not detected in any of the samples, while E. coli concentration was generally lower than 460MPN/g in the sludge accumulated in the beds. The studied systems demonstrated a good efficiency for sludge dewatering and stabilization in the context of small remote wastewater treatment plants. [Copyright &y& Elsevier]

Lime stabilization is a means to raise the pH of biosolids to meet specific pathogen requirements. Along with controlling the microbial growth, lime stabilization reduces the potential for offensive odors. Lime stabilized biosolids can be beneficially used as a soil amendment and also for land reclamation. However, if biosolids are not properly incorporated with the lime, there is a potential for microbial growth, which consequently leads to the emanation of offensive odors and growth of pathogens. Proper mixing was found to be an important factor for the reduction of offensive odors in biosolids treatment. To better understand the effects of mixing on odorous products, bench-scale and full-scale tests were conducted to assess the lime stabilization process and investigate mixing quality at a wastewater treatment plant to help reduce odors associated with known odorants. The results of 4-week laboratory bench-scale tests showed that mixing had the largest effect on odor. The hedonic tone test of the control samples with poor mixing showed a hedonic tone of −2.9 initially and then dropped to −7.3 on Day 29. The hedonic tone of the 3.5%, 7%, and 10% lime mixed biosolids had similar hedonic tones (−2.8 to −2.5) on Day 1 and slightly fluctuated over time and ended at −1.6 to −2.7 on Day 29, which was less odorous than the controls. The control sample with poor mixing showed a rapid pH drop from 12.1 on Day 1 to 8.4 on Day 7. The pH of the control sample was considerably lower than the mixed samples and ended up on Day 28 with a pH of 8.0. The pH of the 7% and 10% samples were relatively stable throughout the 4-week period with a pH still higher than 12 on Day 28. The biosolids with better mixing had a less offensive odor and weaker odor strength than the controls collected at the plant with poor mixing. The lime stabilization process in the wastewater treatment plant was modified in a full-scale study by prolonging the mixing time. The samples collected from the modified process had a less offensive odor and weaker odor strength than the controls from the original lime addition process with short mixing time. The hedonic tone of the two biosolid samples taken from the modified process (−2.5 to −3.0) was less negative than the controls (−3.5 to −4.5). The pH of the biosolid samples taken from the modified process was still above 12 on Day 21, while the pH notably drooped in the controls from 11 on Day 1 to 7.5–8.5 on Day 7. In addition, headspace analysis from both bench and full-scale tests indicated that the sulfur compounds were more prominent in poorly mixed samples than well mixed samples. [Copyright &y& Elsevier]

Abstract: Waste products such as biosolids and wood wastes have been frequently used in container production of plants. The use of biosolids in agriculture is a beneficial mean of recycling the by-products of waste-water treatment. However, care must be taken to avoid environmental or human health problems via run-off and leaching. The objective of this work is to compare the retention capacity of cadmium, lead, zinc and nitrate between pine bark (PB) and coconut fibre (F) when mixed with increasing amounts of composted sewage sludge (CSS) (0%, 15% and 30% (v/v)). Substrates were packed into leaching columns and irrigated with deionised water every 2 days. Leachates were collected during 1 month, and nitrate, Zn, Cd, Pb, EC and pH were monitored along the experiment. PB columns leached lower amount of nitrate than the coconut fibre ones. The same trend was observed for Zn, Cd and Pb. It could be said, that in order to minimize the environmental risks of using sewage sludges our results indicate that it is preferred to mix the sludge with pine bark instead than with coconut husk. [Copyright &y& Elsevier]

Abstract: The aim of this work was to determine the potential application of dried sewage sludge as a biosorbent for removing phenol from aqueous solution. Results showed that biosorption capacity was strongly influenced by the pH of the aqueous solution with an observed maximum phenol removal at pH around 6–8. Biosorption capacity increased when initial phenol concentration was increased to 110mg/L but beyond this concentration, biosorption capacity decreased suggesting an inhibitory effect of phenol on biomass activity. Biosorption capacity decreased from 94 to 5mg/g when biosorbent concentration was increased from 0.5 to 10g/L suggesting a possible competitive effect of leachable heavy metals from the sludge. The effect of Cu2+ on biosorption capacity was also observed and the results confirmed that the phenol biosorption capacity decreased when concentration of Cu2+ in the sorption medium was increased up to 15mg/L. Desorption of phenol using distilled deionized water was less than 2% suggesting a strong biosorption by the biomass. [Copyright &y& Elsevier]

Abstract: The high water content of sewage biosolids makes them expensive to transport. Two experiments were done to see if it was practical to use transpiration by plants as a low cost method to dehydrate biosolids. (i) To assess biosolids as a growth-medium for plants, maize, beans, pumpkin, forage oats and an annual ryegrass were grown in pots of fresh biosolids. Plant growth varied between species and potassium deficiency was found to be a limiting factor for barley. Roots were slow to penetrate anoxic biosolids in the bottom of the pots. (ii) Dehydration rates were measured in 30 litre boxes of biosolids from two different sources. Boxes were planted with maize or beans, or kept fallow. Despite the high (73–83%) initial water content of the biosolids, plants were susceptible to wilting on warm days which suggested that a significant proportion of the water in biosolids is not freely available to plants. Shrinkage caused a major reduction in biosolids volume in both experiments. When change in volume of the biosolids residue was accounted for, there was a 56% average water loss in planted treatments and 34% water loss in the fallow treatment. This indicates that planting may have some potential as a technique to accelerate dehydration of biosolids. Water contents were not reduced sufficiently to influence biosolids microbial populations. [Copyright &y& Elsevier]

Abstract: This is the second of two papers presenting the data from an experiment on the application of aerobically-digested sewage sludge (AES), anaerobic lagoon septic wastes (ANS), sewage sludge compost and fertilizer to soils for grass forage and feed corn production at two different sites in Nova Scotia. Crop yields, plant tissue and Mehlich-1 extractable soil nutrients were evaluated; 15 elements were analyzed in the plant tissue and 9 elements in the soil extracts. This paper describes the Ca, Mg, S, Fe, Mn, Cu, Zn and B content of the crops and the Mehlich-1 extractable content of the soils. The response to the amendments was not consistent at the two sites with the two different crops. We found that the septic sludge (ANS) produced the highest forage Fe, Cu and Zn levels and was equal to compost in elevating corn stover and forage S and the forage B content. The compost produced the highest forage Ca and corn Zn, the AES produced the highest corn Mn, and fertilizer produced the highest forage Mn. None of the amendments produced excessive levels of the above nutrients; rather, the amendments improved the feed quality of the forage and corn stover. Lastly, it was noted that the Mehlich-1 extract only had a significantly positive correlation with forage Cu content. [Copyright &y& Elsevier]

Abstract: This paper presents the data from two years of experiments concerned with the application of aerobically-digested sewage sludge, anaerobic lagoon septic sludge, sewage sludge compost or fertilizer to soils for grass forage and feed corn (Zea mays L.) production at two different sites 45km from Truro, Nova Scotia. Crop yields, plant tissue and Mehlich-1 extractable soil nutrients were evaluated; 15 elements were analyzed in the plant tissue and nine elements in the soil extracts. This paper describes the results of crop yields, plant N, P and K content and Mehlich-1 extractable P and K. The research demonstrated the fertilizer produced higher yields of grass forage than the sludge and the compost but equivalent to the sludge in corn yields. Forage and corn N, P and K contents, however, varied with treatment, crop and year, while the compost-amended soils were highest in extractable nutrients. Both sludges and the compost, therefore, could be effective sources of N, P and K for crop production. Compared to the conventional fertilizer, the nutrient availability from the organic amendments (especially N and P) was considerably lower than the 50% assumed at the start of the experiment; the sludges however, provided higher nutrient availability than the compost. [Copyright &y& Elsevier]

Abstract: Humic substances and three hydrolytic enzymes (β-glucosidase, phosphatase and urease) were extracted by neutral sodium pyrophosphate from an olive waste (dry olive cake), alone or mixed with municipal biosolids, during a nine month vermicomposting process. Easily degradable compounds decreased during the vermicomposting process because of microbial consumption. When municipal biosolids were added to dry olive cake, microbial activity increased and the amounts of compounds extracted by pyrophosphate were three times lower than olive cake alone. In both instances, β-glucosidase, phosphatase and urease activities of the organic extracts either increased or remained the same after a nine month period of vermicomposting, thus suggesting that the humus enzyme complexes resisted microbial and earthworm attack. It is known that humus immobilised enzymes also remain active in soil environments, reactivating the nutrient cycles in soil. The use as amendments of vermicomposted olive cake, alone or when mixed with biosolids, could be a good alternative to reactivate the C, P and N-cycles in degraded soils for regeneration purposes. [Copyright &y& Elsevier]

Three sludge types from the same treatment stream (undigested liquid, anaerobically digested liquid and dewatered, anaerobically digested cake) were used in a field based tub study. Amendments (4, 8, and 16 Mg dry solid (ds) ha−1) were incorporated into the upper 15 cm of a sandy loam soil prior to sowing with rye-grass (Lolium perenne L.). Nitrogen transformations in the soil were determined for the 80 d period following incorporation. Nitrogen uptake and crop yield were measured in the cut sward 35 and 70 d after sowing. The study showed that application of sewage sludge at rates as low as 4 Mg ha−1 can have a nutritional benefit to rye-grass over the two harvests. Differences in N transformation, and hence crop nutritional benefit, between sludge types were evident throughout the experiment. In particular, the dewatering process changed the mineral N characteristics of the anaerobically digested sludge, which, when not dewatered, outperformed the other sludges in terms of yield and mineralisation rate at both harvests. The dewatered sludge produced the lowest yield of rye-grass. The undigested liquid sludge had the lowest foliar N and soil NO3–N concentrations, possibly immobilised as the large oxidisable C component of this sludge was metabolised by the microbial biomass. Correlation data support the concept of preferential uptake of NH4–N over NO3–N in Lolium perenne. Results are discussed in the context of managing sludge type and application for a plant nutrient source and NO3–N release. [Copyright &y& Elsevier]

Sewage biosolids contain high concentrations of pathogens, which limits their use as soil amendment. This study investigated how application of lime (Ca(OH)2), irradiation, or pasteurization reduced pathogens in biosolids and how its application affected soil characteristics. A soil sampled outside the canopy of Mesquite trees (Prosopis laevigata) and from a pasture at Lerma (Mexico) was amended with treated or untreated biosolids, characterized and incubated aerobically while dynamics of carbon (C), nitrogen (N) and phosphorus (P) were monitored. Heavy metals concentrations in the biosolids were low, so it was of excellent quality (USEPA). The amount of pathogens in the biosolids made it a class “B” (USEPA) which can be used in forests. Only irradiation sufficiently reduced faecal coliforms to make it a class “A” biosolids without restrictions in application. C mineralization increased significantly when biosolids were added, but not concentrations of available P (P<0.05). Ammonium (NH4+) concentrations in soil amended with biosolids were higher compared to unamended soil, but not the concentrations of nitrate (NO3−) except when biosolids treated with Ca(OH)2 was added to the Lerma soil. [Copyright &y& Elsevier]

[Display omitted] • CM addition for direct interspecies electrons transfer can enhance AD performance. • Research to date is limited to carbon and iron based CMs using small scale reactors. • Future work at pilot scale is recommended to validate the benefits of CM addition. • Future work is also to access the impact of CM addition on downstream processing. Addition of conductive materials (CMs) has been reported to facilitate direct interspecies electron transfer (DIET) and improved anaerobic digestion (AD) performance. This review summarises the benefits and outlines remaining research challenges of the addition of CMs with a focus on the downstream processing of AD. CM addition may alter biogas quality, digestate dewaterability, biosolids volume, and centrate quality. Better biogas quality has been observed due to the adsorption of H 2 S to metallic CMs. The addition of CMs results in an increase in solid content of the digestate and thus an additional requirement for sludge dewatering and handling and the final biosolids volume for disposal. This review highlights the need for more research at pilot scale to validate the benefits of CM addition and to evaluate CM selection, doses, material costs, and the impact on downstream processes. The lack of research on the impact of CMs on the downstream process of AD is highlighted. [ABSTRACT FROM AUTHOR]