Academic literature on the topic 'Biosolids characterisation'

Sewage sludge, often referred to as biosolids, is generated in large quantities by wastewater treatment plants. It contains macro- and micronutrients which are essential for plant growth and so represents a valuable agricultural resource. Prior to land application, pathogens are carefully monitored to reduce the risk of crop and soil contamination however to date there has been limited investigation of agriculturally beneficial bacteria indigenous to the biosolids. This study investigated shifts in the composition of the bacterial community alongside the physicochemical properties of biosolids of increasing age, from freshly dewatered to those stockpiled for approximately four years. With stockpiling, there was a significant increase in ammonium content, ranging from 801 mg/kg in the fresh biosolids to 8178 mg/kg in the stockpiled biosolids and a corresponding increase in pH ranging from 6.93 to 8.21. We detected a ten-fold increase in Firmicutes, from 4% relative abundance in the fresh biosolids compared to 40% in the older, stockpiled biosolids. Plant growth promoting bacteria (PGPB) of the Proteobacteria family, particularly of the Devosia and Bradyrhizobium genera were identified in the freshly dewatered and the older, stockpiled biosolids. Land application of the biosolids studied here could reduce fertiliser costs, provide a means of pH correction to acidic soils and a potential source of bacteria beneficial for crop growth.

Organomineral fertilisers (OMFs) were produced by coating biosolids granules with urea and potash. Two OMF formulations with N : P2O5 : K2O compositions: 10 : 4 : 4 (OMF10) and 15 : 4 : 4 (OMF15) were developed for application in grassland and arable crops. Routine fertiliser analyses were conducted on four batches of OMF and biosolids granules and compared with a sample of urea to determine key physical and chemical properties of the materials which affect handling and spreading, soil behaviour, and fertiliser value. Bulk and particle densities were in the range of 608 to 618 kg m−3, and 1297 to 1357 kg m−3, respectively. Compression tests showed that OMF particles undergo deformation followed by multiple failures without disintegration of the granules when vertical load was applied. Static particle strength was between 1.18 and 4.33 N mm−2depending on the particle diameter. The use of a model for fertiliser particle distribution studies showed that OMF granules should be between 1.10 and 5.50 mm in diameter with about 80% of the particles in the range of 2.25 to 4.40 mm to enable application at 18 m tramline spacing. This research utilises novel technology to improve the fertiliser value of biosolids, reduce disposal costs, and deliver a range of environmental benefits associated with recycling.

Ireland is an island country on the western boundary of the European Union. A suite of environmental legislation over the last decade has combined to increase the amount of municipal sludge for treatment fourfold, while, simultaneously, eliminating traditional disposal methods. The Irish Government has instituted a comprehensive programme of policy development, infrastructure provision and drafting of “codes of good practice” to meet these environmental and legislative challenges. As the programme has developed, it has become clear that the sludge/biosolids issue shares many of the philosophical and logistical elements of other environmental issues that are developing apace in Ireland, including municipal waste management, agricultural waste management and overall integrated development. In many ways, it represents a model of the ultimate “sustainable development” issue. To provide specific data for decision making and policy/infrastructure/technology development, the Irish Government has funded a US$600k programme of research in The Characterisation, Treatment and Sustainable Reuse of Biosolids. The design philosophy of the programme is a “cradle-to-grave” approach, in order to integrate the outcomes of specialised research studies into an overall sustainable development model.

Characterisation tests were conducted to determine the feasibility of land application of the sludges produced in wastewater treatment by means of Fenton's Reagent. Physicochemical and microbiological parameters of Fenton sludges were compared to the values obtained for raw alum sludges. The Fenton sludges presented preferable characteristics such as the specific resistance to filtration (SRF), metals and pathogen content (fecal and total coliforms, helminth ova, and Salmonella sp.). The SRF of the Fenton sludges (1.55 × 1013 m/kg) was 24% less than the alum sludge value (1.92 × 1013 m/kg). The concentrations of fecal coliforms (0 MPN/g TS), Salmonella sp. (0 MPN/g TS), Helminth ova (22 HH/g TS) and metals correspond to the limits for biosolids of Class B for land application of the Mexican legislation. The Fenton reagent efficiently removes most of the pathogens, considered by the norms, by means of the combined action of the different stages that constitute this process. These results exhibit the Fenton reagent as a feasible treatment for generating sludges with characteristics of biosolids of Class B for land application. The preliminary results of conditioning tests show that Fenton sludges present better dewatering characteristics with regard to the alum sludge, for a dose of cationic polymer of 1 mg/g TS.

El propòsit del treball es caracteritzar hidrodinàmicament els tancs més utilitzats en el sector aqüícola, i donar pautes de disseny per millorar-ne l'autoneteja, i optimitzar l'eficiència d'utilització tant de l'espai com de l'aigua. La tesis es presenta en forma de compendi d'articles. En els dos primers s'estudien les característiques hidrodinàmiques de diferents configuracions geomètriques i diferents dissenys d'entrada d'aigua. En els dos últims s'estudien els processos de sedimentació i resuspenció dels biosolids que es generen en els tanc aqüícoles, mesurant la turbulència necessària per la sedimentació i resuspenció, i posteriorment es varen comparar els valors obtinguts amb els de la turbulència generada per la pròpia activitat natatòria del peixos en els tancs de cultiu.
L'estudi de les característiques hidrodinàmiques dels tancs, es va realitzar amb models a escala al laboratori, que es van evaluar mitjançant velocimetria de seguiment de partícules. La turbulència generada pels peixos al nedar es va estudiar mitjançant velocimetria acústica, utilitzat la mitja quadràtica de les velocitats (Root Mean Square RMS) com a paràmetre per quantificar la turbulència. Finalment, la turbulència necessària per la resuspenció de biosolids es va determinar amb una graella oscil·lant adaptada a les característiques dels biosolids aqüícoles (alt contingut orgànic, i alta cohesivitat); l'RMS també fou el paràmetre utilitzat per quantificar la turbulència necessària per la resuspenció de biosolids.
Amb l'estudi de les característiques hidrodinàmiques dels models a escala, s'ha determinat que el patró de flux està fortament condicionat pel disseny de l'entrada d'aigua.
S'ha observat que en les configuracions on l'aigua fluïa de d'un extrem del tanc a l'altre, el patró de flux era molt heterogeni amb presència freqüent de zones mortes i corrents de curt-circuit. Les velocitats aconseguides foren baixes. Es van aconseguir velocitats més altes i una major homogeneïtat quan es va introduïr l'aigua tangencialment a la paret del tanc per tal de crear cèl·lules de barreja. Les cèl·lules de barreja van presentar un flux típic de tancs circulars tot i la geometria rectangular dels tancs utilitzats. Es va definir el paràmetre coeficient de resistència de tanc (Ct), que ha demostrat ser vàlid per evaluar tancs tant circulars com rectangulars amb cèl·lules de barreja. Aquest coeficient ha estat útil per evaluar l'efecte de l'emplaçament de bafles i de les diferents ratios entre longitud i amplada de cèl·lula estudiades. S'ha comprovat que l'efecte dels bafles augmenta les velocitats a la sortida de l'aigua. L'augment d'aquestes velocitats permetrà eliminar els biosòlids del tanc i aconseguir una millor autoneteja.
Referent a l'estudi de l'activitat natatòria dels peixos mitjançant velocimetria acústica, el mètode proposat ha permès determinar que la turbulència generada pels peixos al nedar augmenta amb la densitat, així com l'important efecte que té el fotoperíode en l'activitat natatòria dels llobarros.
Per últim, la utilització de la graella oscil·lant per determinar el nivell de turbulència necessari per resuspendre els biosolids i el nivell necessari per mantenir-los a la columna d'aigua, ha permès determinar l'efecte del temps de consolidació en la turbulència necessària per la resuspenció. També s'ha observat que existeix histèresis quan després d'un procés de resuspenció, la turbulència es va disminuir per evaluar el procés de sedimentació. Finalment, s'han pogut determinar diferències en la turbulència necessària per la resuspenció quan es van evaluar biosolids procedents de diferents tancs, amb diferents densitats de cultiu i talla de peixos.
El propósito del presente trabajo es caracterizar hidrodinámicamente los tanques más utilizados en acuicultura y dar pautas de diseño para mejorar su autolimpieza, y optimizar la eficiencia de utilización tanto del espacio como del agua. La tesis se presenta en forma de compendio de artículos. En los dos primeros se estudiaron las características hidrodinámicas de diferentes configuraciones geométricas y diferentes diseños de entrada de agua. En los dos últimos artículos se estudiaron los procesos de sedimentación y resuspensión de los biosólidos que se generan en los tanques acuícolas, midiendo la turbulencia necesaria tanto para la sedimentación como para la resuspensión, y se compararon los valores obtenidos con los de la turbulencia generada por la propia actividad natatoria de los peces en los tanques de cultivo.
El estudio de las características hidrodinámicas de los tanques se realizó con modelos a escala en laboratorio, que se evaluaron mediante velocimetría de seguimiento de partículas. La turbulencia generada por los peces al nadar se estudió mediante velocimetría acústica, siendo la media cuadrática de las velocidades (Root Mean Square RMS) el parámetro utilizado para cuantificar la turbulencia. Finalmente, la turbulencia necesaria para la resuspensión de biosólidos se determinó mediante una parrilla oscilante adaptada a las características de dichos biosólidos (alto contenido orgánico y alta cohesividad); el RMS también fue el parámetro utilizado para cuantificar la turbulencia necesaria para la sedimentación y resuspensión de biosólidos.
En el estudio de las características hidrodinámicas de los modelos a escala, se ha determinado que el patrón de flujo está fuertemente condicionado por el diseño de entrada del agua. Se ha observado que en las configuraciones en que el agua fluyó des de un extremo del tanque al otro, el patrón de flujo fue heterogéneo con presencia frecuente de zonas muertas y corrientes de corto circuito. Las velocidades alcanzadas fueron bajas. Se consiguieron velocidades más altas y una mayor homogeneidad cuando el agua se introdujo tangencialmente a la pared del tanque para crear células de mezcla. Las células de mezcla presentaron un flujo típico de tanques circulares a pesar de la geometría rectangular del tanque. Se definió el parámetro coeficiente de resistencia de tanque (Ct), que ha demostrado ser válido para evaluar tanques tanto circulares como rectangulares con células de mezcla. Dicho coeficiente ha sido útil para poder evaluar el efecto del emplazamiento de bafles y de las diferentes ratios entre longitud y ancho de célula estudiadas. Se ha comprobado que el efecto de los bafles aumenta las velocidades en la salida del agua. El aumento de estas velocidades permitirá eliminar los biosólidos del tanque y alcanzar una mejor autolimpieza.
Referente al estudio de la actividad natatoria de los peces mediante velocimetría acústica, el método propuesto ha permitido determinar que la turbulencia generada por los peces al nadar aumenta con la densidad, así como el fuerte efecto que tiene el fotoperíodo en la actividad natatoria de las lubinas.
Por último, el uso de la parrilla oscilante para determinar el nivel de turbulencia necesario para resuspender biosólidos y el nivel necesario para mantenerlos en la columna de agua, ha permitido determinar el efecto del tiempo de consolidación en la turbulencia necesaria para la resuspensión. También se ha observado la existencia de histéresis cuando después de un proceso de resuspensión, la turbulencia se disminuyó para evaluar el proceso de sedimentación. Finalmente, se han podido determinar diferencias en la turbulencia necesaria para la resuspensión cuando se evaluaron biosólidos procedentes de diferentes tanques, con diferentes densidades de cultivo y talla de peces.
The purpose of this work is to characterise the hydrodynamics of the most commonly used aquaculture tanks and to define design criteria that will improve self-cleaning properties and optimise the use of space and water. The dissertation is submitted as a compilation of individual articles. Two of the articles focus on the hydrodynamic characteristics of various tank geometries with different water inlet designs. The remaining articles examine the turbulence required for sedimentation and resuspension of biosolids generated in aquaculture tanks. The turbulence values obtained are compared with the turbulence generated by fish swimming activity in aquaculture tanks.
Hydrodynamic characteristics were studied in the laboratory by applying particle-tracking velocimetry techniques to scale models.
The turbulence generated by fish swimming activity was studied using acoustic velocimetry techniques and quantified using the root mean square (RMS) of velocities. Finally, the turbulence needed to resuspend biosolids was determined using an oscillating grid adapted to the specific characteristics of the aquaculture biosolids (high organic content and high cohesiveness); RMS was also used to quantify the turbulence needed to resuspend biosolids.
Analysis of the hydrodynamic characteristics of scale models revealed that the flow pattern is strongly affected by the water inlet design. The flow pattern was homogeneous in configurations in which water flowed along the tank from the upper to the lower end, and dead zones and bypass currents were frequently observed. Flow velocities were low. The homogeneous flow pattern and higher water velocities were observed when water was injected tangentially to create a rotating flow pattern. Rotating flow cells produced a circular flow pattern in rectangular tanks. We defined a tank resistance coefficient (Ct), which was found to be suitable for evaluating both circular and rectangular tanks with rotating flow patterns. The coefficient was used to assess the effect of baffles and various length/width cell ratios. We found that baffles increased the water velocity at the outlets, which is important in the removal of biosolids and for producing self-cleaning properties.
Acoustic velocimetry was used to study fish swimming activity. We found that the turbulence generated by swimming activity increases with density and that the photoperiod has a strong effect on the swimming activity of sea bass.
Finally, an oscillating grid was used to determine the turbulence needed to resuspend biosolids and the turbulence needed to keep them in the water column; these experiments illustrated the effect of consolidation time on the turbulence required for resuspension.
Hysteresis was observed when turbulence was reduced to evaluate sedimentation following resuspension, and different levels of turbulence were required for resuspension in different tanks (with different densities and fish sizes).

Hydrothermal liquefaction (HTL) is a promising thermochemical conversion process to convert biosolids into renewable crude oil. HTL process can be achieved at temperatures between 200 to 350°C, pressures between 50 to 250 bar, and residence time between 1 and 60 minutes. The HTL produces four phases: renewable crude oil, aqueous, gaseous and solid phases. For the process to be upgraded to an industrial scale, it is needed to gain a better understanding of the HTL of biosolids. However, there is limited information to validate the effects of the interactions between the biosolid content under HTL reaction conditions on the yield and the composition of the produced renewable crude oil. The primary objective of this research is to provide a better understanding of the HTL of biosolids, which was achieved through the following detailed objectives. The first objective is to quantify the variability in the biosolids composition to determine the chemical compositions of biosolids. The second objective is to understand how this variable biosolids feedstock behaves through HTL, especially to measure the effects of organic compounds of biosolids: lipids, proteins, carbohydrates, and lignins on the HTL yields. The third objective is to provide a new understating of the characterisation of HTL products from biosolids by identifying the effects of biosolid components and the HTL conditions on both the distributions of the HTL products’ yields and on the qualities of renewable crude oil. The fourth objective is to assess the use of biosolids with dominant organic fraction via different reaction temperatures and residence times on the composition and fractions of the produced renewable crude oil. From the results of the experiments, biosolids have different characters that affect the yield and quality of renewable crude oil. Applying a Van Krevelen diagram to compare biosolids with other biomass indicated that only some biosolids samples have similar characteristics to that of biomass. The difference in the characteristic of the organic content of biosolid samples could depend on several reasons, such as the sources of the biosolids and the treatment process. The effects of the biosolids’ composition on the HTL yield show that lipids and proteins have positive impacts on the renewable crude oil yield, while carbohydrates and insoluble lignin led to an increase in the solid residue. The renewable crude oil contained a high amount of high-boiling point materials in comparison with low-boiling point materials for all biosolids samples used in this study. The effect of the operating conditions, such as temperature was significant. The renewable crude yield usually increases with an increase in temperature until a specific temperature is reached, at which point the renewable crude yield starts to decrease. Various residence times also affected renewable crude oil yields significantly. The optimal residence times depended on the biosolids content and temperature. The HTL of biosolids with different organic fractions resulted in different renewable crude oil compositions, which contained a complex mixture of >300 major compounds that were identified using Gas chromatography-mass spectroscopy analyser. The predominant components identified from the lipid, protein, carbohydrate and lignin constituents were cyclic terpanes and terpenes, along with nitrogenous, oxygenated, and phenolic components. Based on the boiling point of the produced compounds, high gasoline and naphtha-like and high diesel-like yields were produced from biosolid samples with high lipid and protein content, while the kerosene-like best yield was generated from a high lipid sample. A significant gas oil-like yield was produced from the high lipid and carbohydrate biosolid samples, while a high yield of wax, lubricating oil and vacuum gas oil-like contents were generated from the high lignin sample. In summary, the results of the outcomes of this work and the methods used to analyse the chemical compositions of biosolids can form a significant facet of future industrial development of HTL of biosolids, particularly in commercial plants design and management. Finally, it is hoped that the methods presented here, especially the methods used to analyse the chemical compositions of biosolids and the outcomes of this work, especially regarding the composition of the produced renewable crude oil, can form a significant facet of future industrial development of the HTL of biosolids.
Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering and Advanced Materials, 2021