Soluble Nitrogen Research Articles

Biochar from animal manure: A critical assessment on technical feasibility, economic viability, and ecological impact

AbstractAnimal manure has been used to manage soil fertility since the dawn of agriculture. It provides plant nutrients and improves soil fertility. In the last decades, animal husbandry has been significantly expanded globally. Its economics were optimized via the (international) trade of feed, resulting in a surplus of animal manure in areas with intensive livestock farming. Potentially toxic elements (PTEs), pathogenic microorganisms, antibiotic residues, biocides, and other micropollutants in manure threaten animal, human, and environmental health. Hence, manure application in crop fields is increasingly restricted, especially in hotspot regions with intensive livestock activities. Furthermore, ammonia volatilization and greenhouse gas (GHG) emissions during manure storage, field application, and decomposition contribute to air pollution and climate change. Conventional manure management scenarios such as composting and anaerobic digestion partially improve the system but cannot guarantee to eliminate sanitary and contamination risks and only marginally reducing its climate burden. Hence, this review discusses the potential of pyrolysis, the thermochemical conversion under oxygen‐limited conditions as an alternative treatment for animal manure providing energy and biochar. Manure pyrolysis reduces the bioavailability of PTEs, eliminates pathogenic microorganisms and organic micropollutants, and reduces GHG emissions. Pyrolysis also results in the loss of nitrogen, which can be minimized by pretreatment, that is, after removing soluble nitrogen fraction of manure, for example, by digestion and stripping of ammonia–nitrogen or liquid–solid separation. However, conclusions on the effect of manure pyrolysis on crop yield and fertilization efficiencies are hampered by a lack of nutrient mass balances based on livestock unit equivalent comparisons of manure and manure biochar applications. Hence, it is essential to design and conduct experiments in more practically relevant scenarios and depict the observations based on the amount of manure used to produce a certain amount of biochar.

The effect of quinoa germ on the quality properties of fresh whey‐less cheese made by ginger (Zingiber officinale) extract as a coagulant

The effect of ginger extract (GE), as a milk coagulant, was investigated on the physicochemical, proteolysis, textural profiles and sensory properties of whey‐less cheese containing quinoa germ powder (QGP; 0, 3, 6 and 9%) during storage. The results showed that with increasing QGP, the dry matter, fat, soluble nitrogen at pH 4.6 and free tryptophan and tryptophan amino acids increased and protein content decreased. Consequently, it is suggested that using 6% quinoa germ in the production of whey‐less cheese made by GE as a coagulant can give the most desired product with no adverse effects on the quality and sensory properties.

Mutual feeding mechanism of carbon, nitrogen and enzyme activity in Northeast China black soil under snow cover change

Projected future changes in snow cover patterns associated with global warming in cold zone ecosystems could affect soil biochemical cycling. However, the effects of snow cover changes on soil available carbon, nitrogen and enzyme activities and their potential response mechanisms have not been clarified. Therefore, from November 2021 to April 2022, this study conducted a snow depth manipulation test of four treatments in the northeast black soil region, and divided the test period into five stages to measure soil temperature and humidity, microbial biomass, enzyme activity, and available carbon and nitrogen. The results showed that the decrease of snow cover increased the freeze-thaw cycle frequency and freezing temperature of soil, but decreased the soil water content. Soil total organic carbon and inorganic nitrogen contents were increased in early and deep snow periods, while snow treatment was on the contrary. Due to the release of soluble nutrients caused by frequent freeze-thaw processes, Soil soluble organic carbon and Soil soluble organic nitrogen contents increased with the decrease of snow depth in deep snow period, snowmelt period and subsequent early crop growth period. Snow treatment increased soil microbial carbon and nitrogen content in early winter and early spring because snow provided heat insulation. Soil enzyme activities increased with the increase of snow cover. Compared with the control, soil urease activities and sucrase activities increased by 18.5 % and 11.5 % under snow treatment, and decreased by 23.2 % and 10.8 % under snow reduction treatment. In addition, soil soluble organic matter was a controlling factor for soil microbial biomass and enzyme activity throughout winter. The direct effect of soil soluble organic carbon and nitrogen on soil enzymes will make soil enzymes participate in the cyclic transformation process of available carbon, thus forming a closed loop of mutual feedback between soil available carbon and nitrogen and enzymes. These results demonstrated that the changes of snow cover in the future will have certain effects on soil carbon and nitrogen cycles and enzyme activities and hence biogeochemical cycling in terrestrial system of earth.

Odour prevention strategies in wastewater treatment plants: A pilot scale study of activated sludge recycling and oxidized nitrogen recycling

The potential of activated sludge recycling (ASR) and oxidized nitrogen recycling (ONR) to prevent the emissions of H2S and acetic acid from the primary settler during domestic wastewater treatment was herein evaluated. The pilot plant consisted of an 8 L primary settler with a 10 L gas-tight headspace coupled to a 11 L nitrification-denitrification activated sludge reactor and an 8 L secondary settler, which were monitored for 175 days. A reduction in the headspace concentrations of H2S and acetic acid by 95 % and 42 %, respectively, was recorded when combining ASR and ONR. Process operation with ASR and ONR supported stable conditions with average organic matter removals of 96 ± 2 %, NO2- concentrations of 24.2 ± 0.4 mg N/L and NO3- concentrations of 9.8 ± 0.4 mg N/L in the effluent, and a biological oxidation of S2- higher than 99 % with average SO42- concentrations of 52 ± 8 mg/L. Interestingly, the sole recirculation of activated sludge to the primary settler without NO3- recycling caused sludge bulking, contributing to increase the concentration of H2S and acetic acid in the primary settler headspace up to 0.99 ± 0.01 ppmv and 2.87 ± 0.12 ppmv, respectively. Sludge bulking also resulted in an increase in the effluent soluble total nitrogen concentration from 5.6 ± 0.1 mg N/L to 50.8 ± 0.2 mg N/L and of NH4+ from 1.3 ± 0.2 mg N/L to 50.7 ± 0.8 mg N/L due to the loss of nitrification under these operational conditions. Overall, the experimental results indicated that ASR and ONR represent cost-effective strategies for the control of malodorous emissions in wastewater treatment plants.

Designing agricultural grasses to help mitigate proteolysis during ensiling to optimize protein feed provisions for livestock.

The efficient preservation of protein in silage for livestock feed is dependent on the rate and extent of proteolysis. Previous research on fresh forage indicated enhanced protein stability in certain Festulolium (ryegrass × fescue hybrids) cultivars compared to ryegrass. This is the first report of an experiment to test the hypothesis that a Lolium perenne × Festuca arundinacea var glaucescens cultivar had reduced proteolysis compared to perennial ryegrass (L. perenne) during the ensiling process. Forages were harvested in May (Cut 2) and August (Cut 4), wilted for 24 h and ensiled in laboratory-scale silos. Silage was destructively sampled at 0 h, 9 h, 24 h, 48 h, 72 h, 14 days and 90 days post-ensiling, and dry matter (DM), pH and chemical composition were determined. At Cut 2, there was no difference in crude protein between treatments but ryegrass had higher soluble nitrogen (SN) (P < 0.001) and grass × time interactions (p = 0.03) indicated higher rates of proteolysis. By Cut 4, Festulolium had (5.5% units) higher CP than ryegrass (p < 0.001) but SN did not differ. Ammonia-N did not differ between silages in either cut. DM differences (11.8% units) between treatments in Cut 4 (v.2.2% in Cut 2) may have masked effects on proteolysis, highlighting the importance of management on silage quality. This was despite higher WSC in ryegrass in both cuts (p < 0.001), with grass × time interactions (Cut 2; p = 0.03) showing slower WSC decline in ryegrass in Cut 4 (p < 0.001). Silage pH values did not differ between grasses in either cut, but grass × time interactions (p < 0.001) showed a slower decline in both ryegrass cuts, resulting in higher (p < 0.05) pH at 24 h and 72 h for Cuts 2 and 4, respectively. Overall, the hypothesis for an enhanced protein stability in Festulolium when ensiled as ruminant feed was evidenced by lower SN but not ammonia-N in an early-cut silage with a comparable DM to ryegrass.

Impacts of Grazing Disturbance on Soil Nitrogen Component Contents and Storages in a Leymus chinensis Meadow Steppe

Long-term grazing leads to soil degradation in Inner Mongolia grassland. Based on the Hulunbeier meadow steppe, the variation characteristics of soil nitrogen content and storage in soil layers between 0–40 cm, under six different grazing intensities, and the response of vegetation and other physical and chemical properties of soil to grazing were studied. The main results were as follows: (1) Moderate grazing increased soil total nitrogen (TN), soluble total nitrogen (STN) and microbial biomass nitrogen (MBN) contents, while heavy grazing decreased MBN content. In the year with more rain, heavy grazing increased nitrate nitrogen (NO3−-N) content and storage, while less rain increased ammonium nitrogen (NH4+-N) content. (2) The proportion of 0–40 cm nitrogen components showed an upward trend in the year with more rain, and the opposite in the years with less rainfall with the increase of grazing intensity. Soil soluble organic nitrogen (SON) and NO3−-N storages decreased and MBN storage increased in rainy years. (3) Soil nitrogen component contents and storages were correlated with plant growth status, soil moisture (SM) and soil bulk density (SBD), and were significantly negatively correlated with soil temperature (ST) and pH (p &lt; 0.05). The content and storage of soil nitrogen were affected by grazing, soil, vegetation, meteorological and other environmental factors. Moderate grazing was more conducive to the improvement of soil nitrogen storage capacity and the healthy development of grassland.

Determinação de parâmetros do queijo minas artesanal associados com as regiões de origem em Minas Gerais, Brasil

ABSTRACT Artisanal cheese production involves a centuries-old tradition in the state of Minas Gerais in Brazil, playing an important historical and social role. The aim of this study was to evaluate the characteristics of artisanal Minas cheeses from seven regions certified for their production in relation to their physical-chemical and centesimal composition to identify parameters that are useful to differentiate them. There were differences among the cheeses from different regions for the soluble nitrogen variables, extension and depth of ripening indexes, ash, oxidation, fat and pH. The highest values for the ripening length and depth index were observed in the Cerrado region. The cheeses from the Canastra region were different due to the higher moisture content, and the cheeses from Campo das Vertentes presented higher pH and nitrogen compound values. Despite the similarities among cheeses in each region, they had dispersed positions in the principal components analysis. There are differences in the physicochemical and centesimal composition among the artisanal Minas cheeses from the distinct regions in Minas Gerais, and the analyzed parameters can be used to differentiate them. The contents of ash, fat, oxidation index, soluble nitrogen and pH were the parameters that were associated with greater differences in cheeses.

Transcriptomic and physiological responses of a model diatom (Phaeodactylum tricornutum) to heat shock and heat selection

Diatoms are ecologically important phytoplankton as they contribute 40% of the marine primary production and play an essential role in the biogeochemical cycles of many elements. Ocean warming, as a pressing environmental stressor, can profoundly affect the population structure and ecological services of diatoms. However, the molecular mechanisms underpinning cellular and physiological changes of diatoms under heat wave and heat selection conditions remain underexplored. This study revealed the transcriptomic and physiological responses of a model diatom species P. tricornutum to ocean warming at an elevated temperature (25 °C in comparison with 20 °C) under scenarios of heat shock (∼7 days; ∼7 generations) and heat selection (∼175 days; ∼165 generations). While unchanged cell growth and reduced Fv/Fm were recorded in the heat shock treatment, significant reductions in the cell growth rate and Fv/Fm were evident in the heat selection treatment. Contents of Chl-a, carotenoid, total soluble protein, carbon (C), and nitrogen (N) increased significantly in both treatments. Transcriptomics analysis showed that elevated temperature suppressed signaling pathways related to photosynthesis but activated signaling pathways involving in fatty acid metabolism and nitrogen metabolism following the heat selection, associated with elevated substance storage and enlarged cell size. As a result, the increase of both C and N suggest that more energy was likely allocated to growth than division under ocean warming. Notably, P. tricornutum showed a higher resistance to nitrogen limitation condition after acclimating to ocean warming possibly by activation of nitrogen metabolism and uptake. P. tricornutum responded to the projected ocean warming through readjusting energy metabolism.

Effects of adding corn steep liquor on bacterial community composition and carbon and nitrogen transformation during spent mushroom substrate composting

BackgroundCarbon and nitrogen are essential energy and nutrient substances in the composting process. Corn steep liquor (CSL) is rich in soluble carbon and nitrogen nutrients and active substances and is widely used in the biological industry. Nonetheless, limited research has been done on the effect of CSL on composting. This work firstly reveals the effect of adding CSL to bacterial community composition and carbon and nitrogen conversion during composting. This study provides the choice of auxiliary materials for the spent mushroom substrate compost (SMS) and some novel knowledge about the effect of bacterial community on C and N cycling during composting of SMS and CSL. Two treatments were set up in the experiment: 100% spent mushroom substrate (SMS) as CK and SMS + 0.5% CSL (v/v) as CP.ResultsThe results showed that the addition of CSL enhanced the initial carbon and nitrogen content of the compost, altered the bacterial community structure, and increased the bacterial diversity and relative abundance, which might be beneficial to the conversion and retention of carbon and nitrogen in the composting process. In this paper, network analysis was used to screen the core bacteria involved in carbon and nitrogen conversion. In the CP network, the core bacteria were divided into two categories, synthesizing and degrading bacteria, and there were more synthesizing bacteria than degrading bacteria, so the degradation and synthesis of organic matter were carried out simultaneously, while only degrading bacteria were found in the CK network. Functional prediction by Faprotax identified 53 groups of functional bacteria, among which 20 (76.68% abundance) and 14 (13.15% abundance) groups of functional bacteria were related to carbon and nitrogen conversion, respectively. Adding CSL stimulated the compensatory effect of core and functional bacteria, enhanced the carbon and nitrogen transformation ability, stimulated the activity of low-abundance bacteria, and reduced the competitive relationship between the bacterial groups. This may be why the addition of CSL accelerated the organic matter degradation and increased carbon and nitrogen preservation.ConclusionsThese findings indicate that the addition of CSL promoted the cycling and preservation of carbon and nitrogen in the SMS composts, and the addition of CSL to the compost may be an effective way to dispose of agricultural waste.

Effects of Different Carbon Inputs on Soil Stoichiometry in Tianshan Mountains

Soil C, N, and P elements are important components of the forest ecosystem. Studying the influence of exogenous carbon input change on the stoichiometry of the forest soil can reveal the element recycling process and the balanced feedback mechanism of the forest ecosystem. In this study, using the research object of a spruce forest in Tianshan Mountain, the short-term effect of exogenous carbon input on soil C, N, and P in the soil was analyzed through Detritus Input and Removal Treatment (DIRT), and then the interrelationship between soil stoichiometry and other soil physicochemical factors under different treatments was discussed. The results showed that:① the soil C, N, and P contents in most soil layers were the highest double litter (DL) treatment, soil ω(C) by soil depth from shallow to deep was 168.92, 119.88, 103.33, and 64.23 g·kg-1; soil ω(N) was 10.60, 9.32, 8.78, and 8.07 g·kg-1; soil ω(P) was 0.50, 0.45, 0.37, and 0.36 g·kg-1; in the no input (NI) treatment, soil ω(C) by soil depth from shallow to deep was 104.56, 89.24, 48.08, and 43.96 g·kg-1; soil ω(N) was 6.83, 2.60, 2.63, and 2.22 g·kg-1; soil ω(P) was 0.40, 0.34, 0.32, and 0.22 g·kg-1; and a decreased trend was shown with the deepening of the soil layer. Except in the NI treatment, C:N was 0-10 cm and significantly higher than that in other soils (P<0.05), NL soil C:P at 30-50 cm was significantly higher than that in other soils, and NI soil N:P was 0-10 cm and significantly higher than that in other soils (P<0.05). ② Microbial carbon, nitrogen, and phosphorus were significantly higher from 0-10 cm than that in other soil layers (P<0.05). ③ Redundancy analysis results showed that soluble organic carbon and microbial nitrogen at different carbon input levels were important factors affecting the stoichiometric characteristics of soil C, N, and P.

Products and Properties of Components from Heat-Denatured Peanut Meal Following Solid-State Fermentation by Aspergillus oryzae and Saccharomyces cerevisiae

In heat-denatured peanut meal (HDPM), proteins are denatured and polysaccharides are degraded and browned. It can only be used as feed or fertilizer, and not using it as such is a waste of resources. To achieve high-value HDPM use, solid-state fermentation by Aspergillus oryzae and Saccharomyces cerevisiae was investigated. Conditions were optimized by response surface methodology and high-value antioxidant peptides (APs), nonstarch polysaccharides (NSPs), and fermentation products of heat-denatured peanut meal (FHDPM) were obtained. Optimal culture conditions were strain ratio 6:5, inoculation volume 2 mL, and fermentation for 42 h at 35 °C. Under optimal conditions, the theoretical soluble nitrogen concentration, 1,1-Diphenyl-2-picrylhydrazyl radical scavenging rate, hydroxyl free radical scavenging rate, and NSP yield reached 44.78 mg/mL, 62.44%, 94.95%, and 3.73%, respectively; however, their experimental values were 46.80 ± 1.23 mg/mL, 72.18 ± 0.78%, 96.79 ± 0.55%, and 4.42 ± 0.21%, respectively. NSPs, Aps, and FHDPM exhibited four higher classes and eight types of antioxidant activities. Moreover, levels of amino acids and trace elements, and physicochemical properties including emulsion activity index, emulsion stability index, foam capacity, foam stability, water holding capacity, and oil absorption capacity were enhanced by fermentation. The results indicate that APs and NSPs could serve as promising natural antioxidants in the food industry, and FHDPM could be used as a new type of high-value nutritional product in the feed industry. The findings provide new insight for comprehensive processing and utilization of HDPM.

Characterization of water−soluble brown carbon in atmospheric fine particles over Xi'an, China: Implication of aqueous brown carbon formation from biomass burning

Brown carbon (BrC) aerosols can affect not only the climate but also human health, however, the light absorption, chemical compositions, and formation mechanisms of BrC are still uncertain, which leads to uncertainties in the accurate estimation of its climate and health impacts. In this study, highly time − resolved brown carbon (BrC) in fine particles was investigated in Xi'an using offline aerosol mass spectrometer analysis. The light absorption coefficient (babs365) and mass absorption efficiency (MAE365) at 365 nm of water−soluble organic aerosol (WSOA) generally increased with oxygen−to−carbon (O/C) ratios, indicating that oxidized OA could have more impacts on BrC light absorption. Meanwhile, the light absorption appeared to increase generally with the increases of nitrogen−to−carbon (N/C) ratios and water−soluble organic nitrogen; strong correlations (R of 0.76 for CxHyNp+ and R of 0.78 for CxHyOzNp+) between babs365 and the N − containing organic ion families were observed, suggesting that the N − containing compounds are the effective BrC chromophores. babs365 correlated relatively well with BBOA (r of 0.74) and OOA (R of 0.57), but weakly correlated with CCOA (R of 0.33), indicating that BrC in Xi'an was likely to be associated with biomass burning and secondary sources. A multiple linear regression model was applied to apportion babs365 to contributions of different factors resolved from positive matrix factorization on water-soluble organic aerosols (OA) and obtained MAE365 values of different OA factors. We found that biomass-burning organic aerosol (BBOA) dominated the babs365 (48.3 %), followed by oxidized organic aerosol (OOA, 33.6 %) and coal combustion organic aerosol (CCOA, 18.1 %). We further observed that nitrogen−containing organic matter (i.e., CxHyNp+ and CxHyOzNp+) increased with the increase of OOA/WSOA and the decrease of BBOA/WSOA, especially under high ALWC conditions. Our work offered proper observation evidence that BBOA is oxidized through the aqueous formation to produce BrC in Xi'an, China.

STUDY OF THE KINETICS OF MILK KEFIR USING SOY GERM AS SUBSTRATE

The main objective of this study was to analyze the growth kinetics of milk kefir on bean sprouts (Glycine max) as a germinated substrate for 4 days by the glass jar method followed by extracts. Ratio 1:3 (soy: water). 3% kefir grains (activated) inoculated with soluble bud extracts. The soluble extract of bean sprouts has a total sugar content of 5.57% and a fermentable carbohydrate of 3.37 g / L (sucrose), which is a source of nutrition and energy reserves; 1.40% of lipids are used for catabolic grain activity, while protein increases the amount of soluble nitrogen by 6.66%. The pH is 6.67 and the acidity is 0.17%, inversely proportional to lactic acid. The number of microbial populations of soluble extracts of kefirada sprouts reached the logarithmic stage of development after 24 hours for lactic acid bacteria and 48 hours for acetic acid bacteria and yeast, consuming the nutrients of the beverage, influencing its metabolites on the pH of the medium; The period of decomposition of lactic acid bacteria, acetic acid and yeast is 72 hours, and the medium lacks nutrients. The symbiotic action of milk kefir using soluble sprouted extracts is mutual, as the microorganisms it contains grow synergistically and create favorable changes in pH and acidity, depletion of nutrients and the creation of an appropriate environment. To improve the texture it is recommended to combine with fruits or vegetables that contain a lot of sugar.

Annual changes in water quality and sportfish community structure following commercial harvest of common carp and bigmouth buffalo

Martin A. Simonson, Michael J. Weber, Grace M. Wilkinson and Andrew R. Annear. 2023. Annual changes in water quality and sportfish community structure following commercial harvest of common carp and bigmouth buffalo. Lake Reserv Manage. XX:XXX–XXX. Commercial harvest of common carp (Cyprinus carpio; hereafter carp) and bigmouth buffalo (Ictiobus cyprinellus; hereafter buffalo) populations had little detectable effect on shallow lake ecosystems. We tested whether carp and buffalo biomass removal affects limnological variables and fish community metrics across 6 shallow, natural lakes of northwestern Iowa using mixed effects models. Annual commercial harvest of carp ranged from 0 to 71 kg/ha; annual harvest of buffalo ranged from 0 to 356 kg/ha. Biomanipulation (i.e., commercial harvest) of carp was associated with decreases in soluble phosphorus and nitrogen concentrations, but not total phosphorus or nitrogen. Buffalo harvest was unrelated to annual changes in nutrient concentrations but was associated with reductions in chlorophyll a and phycocyanin concentrations. Secchi disk transparency and total suspended solids were unrelated to carp and buffalo harvest. Carp harvest was associated with reduced biomass of large cladocerans but no other zooplankton biomass densities; buffalo harvest was unrelated to zooplankton biomass. Species richness and rake density of aquatic macrophytes were unrelated to carp and buffalo harvest. Carp and buffalo harvest was unrelated to changes in most indices of sportfish abundance, condition, and size distribution. Our results suggest harvest of carp and buffalo <71 kg/ha has little effect on abiotic and biotic ecosystem components on short time scales and highlights the challenges associated with shallow lake restoration.

Influence of dietary grape pomace supplementation on chemical and sensory properties of ewes' cheese

The nutritional and sensorial properties of Pecorino cheese made from milk of ewes fed a diet formulated with grape pomace (GP), a winemaking by-product, were evaluated. Dietary inclusion of GP (GP+) did not influence cheese moisture or total lipid content; however, a significant reduction of C14:1 cis-9 was noted, assumed to be a dietary effect on stearoyl-CoA desaturase function. The amount of β-casein was increased in GP+ samples, but total and TCA soluble fraction nitrogen did not indicate any marked effect on the proteolytic processes. Analysis of volatile compounds showed lower relative percentages of aldehydes, ketones, esters and lactones in GP+ cheeses, indicating improved oxidative stability during ripening. There was a marked decrease of lightness and an increase of hardness, gumminess and resilience (Young's modulus) in the GP+ samples. Sensory analysis of 120-day ripened cheeses confirmed these findings, and highlighted an increase in odour intensity and saltiness.

An Inexpensive, Reproducible Method to Quantify Activated Sludge Foaming Potential: Validation through Lab-Scale Studies and Year-Long Full-Scale Sampling Campaign.

Activated sludge is a conventional treatment process for biochemical oxygen demand (BOD) and total suspended solids (TSS) removal at water resource recovery facilities (WRRFs). Foaming events are a common operational issue in activated sludge and can lead to decreased treatment efficiency, maintenance issues, and potential environmental health risks. Stable foaming events are caused by biological and chemical drivers (i.e., microbes and surfactants) during the aeration process. However, foaming events are difficult to predict and quantify. We present an inexpensive and easy-to-use method that can be applied at WRRFs to quantify foaming potential. Subsequently, the method was applied over a year long full-scale study while data on microbial community composition and functional parameters associated with foaming potential were collected from activated sludge samples at South Shore Water Reclamation Facility (WRF) (Oak Creek, WI). Results from the development of the foaming potential method using linear alkylbenzene sulfonate (LAS) showed that the method was reproducible (relative standard deviation < 20%) and able to capture changes in foam inducing constituents. Using full-scale activated sludge samples, higher relative abundance values for the following genera were associated with foaming events: Zoogloea, Flavobacterium, Variovorx, and Bdellovibrio. This is the first report that Variovorx and Bdellovibrio relative abundance was correlated with foaming events in activated sludge. Furthermore, the foaming potential positively correlated (p ≤ 0.05) with soluble total nitrogen. Characterizing foaming events through frequent sampling, and monitoring of specific genera and functional parameters may allow for predictions and preemptive mitigation efforts to avoid negative consequences in the future.

Membrane distillation for separation and recovery of valuable compounds from anaerobic digestates

Digestate - the wet by-product of the anaerobic digestion (AD) of organic waste - is composed of a mixture of residual organic matter, microbial biomass and inorganic compounds. Although digestate is rich in nutrients, the occurrence of high levels of salinity and soluble ammoniacal nitrogen (N-NH4+) limits its direct exploitation as organic fertilizer and imposes a complex disposal.This study assesses at laboratory-scale the potential of Direct Contact Membrane Distillation (DCMD) for the separation of nutrients and the recovery of water from the liquid phase of the digestate produced by a digester that treats cattle manure and agricultural residues. Experimental tests, carried out at different feed temperature (50–70 °C) and initial pH (6–8.2) of the liquid digestate, aimed at investigating the effect of the operating conditions on the transmembrane flux of water vapor, the concentration of N-NH4+, P-PO3-, and Chemical Oxygen Demand (COD) in both permeate (also referred to as distillate) and retentate streams.For raw digestate, the initial transmembrane flux enhanced from 1.83 L·m−2·h−1 to 5.55 L·m−2·h−1, in response to increasing temperature gradient. Overall, the highest achieved water recovery factor was 40% at a feed temperature of 70 °C. The pH had a limited impact on the transmembrane flux, whereas notably affected the DCMD performance in terms of separation efficiency. In particular, a pH reduction from 8.2 (raw digestate) to 6 was able to completely avoid the transfer of N-NH4+ into the distillate. Compared to the concentration in the raw digestate, the reduction of COD and P-PO3- in the distillate was 99.0% and 99.9%, respectively. Regardless feed temperature, the performance of the process was subjected to a significant decline of evaporation rate due to occurrence of membrane fouling; however, cycles of cleaning with citric acid allowed to partially regenerate the membrane by removing the reversible cake of foulants accumulated on the surface. The results demonstrate an adequate performance of MD process for recovering water and nutrients, leading to a dehydrated fraction of the digestate phase that can be easily stored and used in agronomic practices.

Effect of Type of Milk and Storage Period on the Quality of Hard Cheese*

The objective of this study was to determine the effect ofstorage period on the chemical composition of hard cheese (“Roomi”),manufactured from cow and goat milks and their blends (1:1). A starterculture 1% of Streptococcus thermophills and Lactobacillus bulugaricusand rennet tablet (one tablet /50 litre milk) were used. The curd wascheddared, salted, moulded, pressed overnight, coated with paraffin waxand stored at 12±2ºC for ripening. The proximate analysis of cheesesreflected changes in total solids, total protein and fat contents towardsripening. Cheese prepared from goat milk recorded higher level of solidsand fat than cow and blend cheeses. Cow cheese showed significantly(P≤0.05) higher level of protein than goat and blend cheeses. The pH ofthe three types of cheeses significantly (P≤0.05) decreased inconcomitance with increase in their titratable acidity of all cheeses. Thesoluble nitrogen content increased significantly (P≤0.05) during ripeningof all cheeses. The ratio of soluble nitrogen to total nitrogen alsoincreased significantly (P≤0.05) during ripening of all cheeses.

Wet scrubbing process with oxidation and reduction in series for removal of SO2 and NO from marine diesel engine exhaust

A novel wet scrubber comprising of an oxidation and a reducing section in series was used for the removal of SO2 and NOx from simulated ship emissions. Sodium chlorite (NaClO2) and sodium thiosulfate (Na2S2O3) were used for the oxidizing and reducing sections, respectively. Results showed that although increasing the pH of the chlorite oxidant led to less NO being oxidised, lower rates were achieved for both soluble nitrogen formation (chiefly in the form of nitrates) and reactant consumption per mole of pollutant removed. On the reduction side, it was shown that although the more well-known sulfite (Na2SO3) was about 15% more efficient in removing NO2 compared to thiosulfate, the latter had a very low reactant consumption rate, about 118 and 27 times less compared with sulfite and formaldehyde-stabilised sulfite. The formation of soluble nitrogen was also very low for thiosulfates (less than 0.18 mols formed per mole of NOx removed) or between 1.6 and 1.8 times less when compared with sulfites, as most of the pollutant was reduced to harmless N2. Although thiosulfates formed sulfur precipitates during reaction, this could be circumvented by operating at a high pH. A certain percentage of washwater from the scrubbers can also be discharged, with mixing from the oxidation and reduction sections for the adjustment of oxidation potential, within the allowable nitrate limits.

Benign treatment and resource utilization characteristics of doramectin fermentation residues

Doramectin is a commonly used antiparasitic drug. The biopharmaceutical process to produce doramectin can generate substantial amounts of doramectin fermentation residues, causing environmental risks and increasing economic burden of pharmaceutical enterprises. In the present work, the residual doramectin in the fermentation residues was removed through a low-temperature thermal treatment (LTT) method with temperatures from 160 °C to 220 °C. The degradation products of doramectin and toxicity prediction were assessed, and the impacts of LTT on bioresource properties of doramectin fermentation residues were investigated. The high efficiency for doramectin degradation was achieved by the LTT method, and reached more than 97% at 180–200 °C for 30 min and at 220 °C for 15 min. The olefin, ether and ester groups of doramectin molecule were broken during the LTT process, and higher temperature promoted the production of degradation products with smaller molecular structure. The toxicity prediction demonstrated that the LTT method could mitigate overall acute toxicity for rats of doramectin, and the toxicity of all degradation intermediates was observably reduced at 180 °C. All things considered, the optimal condition for disposing doramectin fermentation residues was recommended at 180 °C for 30 min. The results of synchrotron-based Fourier transform infrared spectroscopy revealed that LTT had little influence on organic functional groups of solid components in doramectin fermentation residues. Under the optimal operating condition of LTT, the contents of soluble total organic carbon, soluble total nitrogen and soluble polysaccharides in doramectin fermentation residues increased by 45.83%, 19.76% and 117.87%, respectively, and the formation and release of humic acid-like matters were also promoted. Generally, the LTT technology may be a promising approach to practically and safely treat doramectin fermentation residues.