Matematički pristup za unapređenje pouzdanosti podešavanja parametara u modeliranju procesa anaerobne digestije

The Nash-Sutcliffe model efficiency coefficient (ENSC) has been modified in order to assess the quality of simulations compared to observed data from the mesophilic monofermentation of grass silage. By applying the ENSC it is not only possible to find parameter sets with the best fit, but also to analyze the sensitivity of each parameter. For modeling the concentration of hydrogen, both the maximum uptake rate for hydrogen km_H2 and half-saturation coefficient of hydrogen KS_H2 are equally sensitive. Modeling the concentration of organic acids as acetate, propionate and butyrate, maximum uptake rate km as well as the free ammonia inhibition constant for acetate uptake KI_NH3 and hydrogen inhibition constants KI_H2, respectively are much more sensitive than their corresponding half-saturation constants KS. Only changes of hydrogen inhibition constants and maximum uptake of acetate compared to the ADM1 suggested values (for mesophilic sludge digestion) were necessary to fit the measurements.Model Nash-Sutcliffe koeficijenta efikasnosti (ENSC) primijenjen je u svrhu procjene kvalitete simulacija u usporedbi s promatranim podacima mezofilne monofermentacije travne silaže. Primjenom ENSC nije moguće pronaći najbolje moguće odgovarajuće skupove parametara, isto tako nije moguće analizirati osjetljivost svakog parametra. Za modeliranje koncentracije vodika, jednako su osjetljivi maksimalna stopa unosa vodika km_H2 kao i poluzasićenost vodikom KS_H2. Modeliranje koncentracije organskih kiselina kao acetata, propionata i butirata, maksimalni unos km jednako kao i konstanta inhibicije bez amonijaka za unos acetata KI_NH3 i konstanta inhibicije vodika KI_H2, mnogo više su osjetljiviji u odnosu na njihove odgovarajuće poluzasićene konstante KS. Za odgovarajuća mjerenja samo su bile potrebne promjene konstante inhibicije vodika i maksimalnog unosa acetate u usporedbi s ADMI predloženim vrijednostima (za mezofilnu digestiju taloga)

Contribution of biochar application to the promotion of circular economy in agriculture

The traditional linear model in agriculture based on the so-called ‘take-make-waste’ has created many problems such as resource scarcity, waste generation, climate change and biodiversity loss. Recently, with the increase in public awareness, the attentiveness in developing a circular economy model was doubled with a focus on proper waste management to bring some benefits to the agricultural sector. Although the increasing acceptance of biochar as a carbon-based material capable of playing a multidimensional role in reducing waste, mitigating climate change, and creating a closed-loop agricultural system, it is still far to move to a final conclusion that biochar application in agriculture could bring attractive environmental and economic benefits. Research conducted so far has led to many insights into how to enhance agricultural sustainability through biochar application, as the impact of biochar is strongly interrelated to their inherent properties, which vary deeply with the nature of biomass and the preparation conditions. In the present study, a systematic literature review was performed to investigate the state- of-the-art research related to the application of biochar in agriculture and its contribution in the establishment of circular economy concept. The interlinking between biochar application in agriculture with energy-water systems and its contribution to successfully build up a circular economy model has also been investigated

Anaerobic digestibility of aerobic granular sludge from continuous flow reactors: the role of granule size distribution

There is an increasing interest in integrating aerobic granular sludge (AGS) technology into wastewater industries. Several projects are being performed to cultivate the aerobic granules for continuous flow reactors (AGS-CFR), while there is a scarcity of those projects that investigate the bio-energy recovery from AGS-CFR. This research was designed to examine the digestibility of AGS-CFR. Beyond that, it aimed at defining the role of the granule size on their digestibility. For this purpose, a series of bio-methane potential (BMP) tests have been run at mesophilic conditions. The results showed that AGS-CFR has a lower methane potential (107.43 ± 4.30 NmL/g VS) compared to activated sludge. This may be the result of the high sludge age (30 days) of AGS-CFR. Additionally, the results revealed that the average size of granules is among the main factors that reduce their digestibility, but it does not inhibit it. It was noticed that granules of size >250 μm have a significantly lower methane yield than the smaller ones. Kinetically, it was noticed that the kinetic models with two hydrolysis rates fit well with the methane curve of AGS-CFR. Overall, this work showed that the average size of AGS-CFR characterizes its biodegradability, which in turn defines its methane yield. HIGHLIGHTS The structural complexity of AGS-CFR reduces its degradability.; The available surface area, EPS, and PN content constrain the hydrolysis rate of AGS-CFR.; Larger aerobic granules have lower methane potential than smaller granules.; Large granules impact the overall digestibility of AGS-CFR.

Efficient Low-Cost Anaerobic Treatment of Wastewater Using Biochar and Woodchip Filters

Access to improved sanitation is often lacking in many low-income countries, and approximately 90% of the sewage is discharged without treatment into receiving water bodies. The aim of this study was the development and evaluation of an efficient low-cost wastewater treatment system for developing countries. Biochar and woodchips, potential locally available and inexpensive materials, were used for anaerobic wastewater filtration and their suitability evaluated in comparison to gravel as a common reference material. Filters were fed with raw sewage from a municipal full-scale wastewater treatment plant in Germany at 22 °C room temperature with a hydraulic loading rate (HLR) of 0.05 m∙h−1. This resulted in a mean organic loading rate (OLR) of 252 gCOD∙m−3∙d−1 and a mean organic surface load of 456 gCOD∙m−2∙d−1. To determine the influence of different filter materials, the removal efficiency of chemical oxygen demand (COD), total organic carbon (TOC), turbidity, and faecal indicator bacteria (FIB) E. coli and enterococci were tested. It was found that COD (up to 90%), TOC (up to 80%), FIB (up to 1.7 log10-units), and turbidity (effluent turbidity below 35 NTU) could be significantly reduced. The findings of this study demonstrate the potential of anaerobic filters (AFs) for wastewater treatment in low-income countries to reduce water pollution and comprehensively improve water quality. The performance of biochar filters was significantly better over the entire experiment compared to woodchip and gravel filters with respect to COD, TOC, turbidity, and FIB removal, indicating the superior properties of biochar for wastewater treatment

Hydraulic modeling of a compact stormwater treatment device applying concepts of dynamic similitude

The development of compact treatment devices (CTDs) with high removal efficiencies and low space requirements is a key objective of urban stormwater treatment. Thus, many devices utilize a combination of sedimentation and upward-flow filtration in a single system. Here, sedimentation is used before filtration, which makes it difficult to evaluate the individual treatment stages separately. This study determines the removal efficiency by sedimentation and the expected filter load in a specific compact treatment device designed for a catchment area of up to 10,000 m2. In contrast to a full-scale investigation, small-scale physical hydraulic modeling is applied as a new cost-saving alternative. To validate upscaling laws, tracer signals and particle-size-specific removal efficiencies are determined for two geometrically similar models at different length scales. Thereby, Reynolds number similarity produces similar flow patterns, while the similarity of Hazen numbers allows to upscale removal efficiencies. Upscaling to the full-scale reveals that the filter in the device is only partly loaded by particulate matter that consists mostly of particles ≤63 μm. Thus, sedimentation upstream of a filter is of relevant importance in CTDs. The proposed dimensionless relationship may be used for particles from different catchments and helps to size the device accordingly. HIGHLIGHTS A small-scale approach is presented to study the gravity-driven removal efficiency in a compact stormwater treatment device that combines sedimentation and filtration.; The Hazen number is successfully applied to scale the gravity-driven removal of particles from a small- to a full-scale model.; The filter stage of the device is only partially loaded with particulate matter, which mostly consists of particles ≤63 μm.

Impact of New Combined Treatment Method on the Mechanical Properties and Microstructure of MICP-Improved Sand

Microbially induced calcite precipitation (MICP) is a green bio-inspired soil solidification technique that depends on the ability of urease-producing bacteria to form calcium carbonate that bonds soil grains and, consequently, improves soil mechanical properties. Meanwhile, different treatment methods have been adopted to tackle the key challenges in achieving effective MICP treatment. This paper proposes the combined method as a new MICP treatment approach, aiming to develop the efficiency of MICP treatment methods and simulate naturally cemented soil. This method combines the premixing, percolation, and submerging MICP methods. The strength outcomes of Portland-cemented and MICP-cemented sand using the percolation and combined methods were compared. For Portland-cemented sand, the UCS values varied from 0.6 MPa to 17.2 MPa, corresponding to cementation levels ranging from 5% to 30%. For MICP-cemented sand, the percolation method yielded UCS values ranging from 0.5 to 0.9 MPa, while the combined method achieved 3.7 MPa. The strength obtained by the combined method is around 3.7 times higher than that of the percolation method. The stiffness of bio-cemented samples varied between 20 and 470 MPa, while for Portland-cemented sand, it ranged from 130 to 1200 MPa. In terms of calcium carbonate distribution, the percolation method exhibited higher concentration at the top of the sample, while the combined method exhibited more precipitation at the top and perimeter, with less concentration in the central bottom region, equivalent to 10% of a half section’s area

Contribution of biochar application to the promotion of circular economy in agriculture

The traditional linear model in agriculture based on the so-called "take-make-waste" has created many problems such as resource scarcity, waste generation, climate change and biodiversity loss. Recently, with the increase in public awareness, the attentiveness in developing a circular economy model was doubled with a focus on proper waste management to bring some benefits to the agricultural sector. Although the increasing acceptance of biochar as a carbon-based material capable of playing a multidimensional role in reducing waste, mitigating climate change, and creating a closed-loop agricultural system, it is still far to move to a final conclusion that biochar application in agriculture could bring attractive environmental and economic benefits. Research conducted so far has led to many insights into how to enhance agricultural sustainability through biochar application, as the impact of biochar is strongly interrelated to their inherent properties, which vary deeply with the nature of biomass and the preparation conditions. In the present study, a systematic literature review was performed to investigate the state- of-the-art research related to the application of biochar in agriculture and its contribution in the establishment of circular economy concept. The interlinking between biochar application in agriculture with energy-water systems and its contribution to successfully build up a circular economy model has also been investigated

Microspheres as Surrogate Helminth Eggs: A Comparative Labscale Sedimentation Study for Tap- and Wastewater

Re-use of water containing helminth eggs during irrigation for agricultural purposes poses health risks, and likewise during research, due to the potential of spreading on contact. Therefore, polystyrene latex microspheres could be used as surrogates for chemical or biological species during colloidal transport. The aim here is to compare the settling velocities of microspheres having varied surface coatings—that is, proteins A, G and A/G; with that of real helminth eggs obtained from literature. The settling velocities of the microspheres were experimentally determined in tap- and wastewater, as well as theoretically in tap water; which was found to be within the range of mean values for those experimentally determined. There were no differences amongst the microspheres types used for settling in wastewater (i.e., A = 0.072 ± 0.02; G = 0.060 ± 0.03; A/G = 0.053 ± 0.01 mm/s). The same applied for settling in tap water (i.e., A = 0.068 ± 0.02; G = 0.047 ± 0.004; A/G = 0.095 ± 0.02 mm/s), except for microsphere G being different from microsphere A/G. All three types of microspheres settled at velocities lower than that of the wastewater particles (=0.118 ± 0.03). T-test analyses of settling velocities of microspheres in both tap- and wastewater, versus that from literature (i.e., Ascaris, Trichuris and Oesophagostomum), showed that microsphere A and A/G may surrogate for Ascaris in tap water, the same as A/G for Oesophagostomum. In wastewater however, both microspheres A and G are a good fit for Trichuris

Olive mill wastes

Olive oil extraction has recently experienced a continuous increase due to its related beneficial properties. Consequently, large amounts of olive mill wastes (OMWs) derived from the trituration process are annually produced, causing serious environmental problems. The limited financial capabilities of olive mills make them usually unable to bear the high costs required for the disposal of their wastes. Alternatively, the valorization of OMWs within the framework of the so-called waste-to-resource concept and their recycling can represent a successful strategy for the implementation of circular economy model in the olive industry, which could have significant socioeconomic impacts on low-income Mediterranean countries. There is, however, no unique solution for OMWs valorization, due to the wide variety of the wastes’ composition and their seasonal production. In this review, the potential of OMWs for being reused and the recent technological advances in the field of OMWs valorization are assessed. Special focus is given to the analysis of the advantages and limitations of each technology and to reporting the most significant issues that still limiting its industrial scale-up. The information collected in this review shows that OMW could be effectively exploited in several sectors, including energy production and agriculture. OMWs potential seems, however, undervalued, and the implementation of sustainable valorization strategies in large-scale remains challenging. More efforts and policy actions, through collective actions, encouraging subsidies, and establishing public–private collaborations, are still needed to reconcile research progress with industrial practices and encourage the large-scale implementation of the waste-to-resource concept in the olive sector