1,721,146 research outputs found
Sequencing Batch Biofilter Granular Reactor (SBBGR) for wastewater treatment and irrigation reuse
Full text linkIn the last decades, both world governmental organizations and public opinion have become aware of water as a precious and limited resource. The increase in world population and climate change suggest the need for a more rational use of water, the reuse of treated wastewater turns out to be a promising strategy to preserve water resources and increase the availability of water in different sectors.
The technologies used for wastewater treatment are based primarily on activated sludge systems. These technologies have several limitations such as the need for large treat-ment surfaces, low biomass settling properties and high excess sludge production, but above all, they do not guarantee sufficient pathogens removal in case of reuse of treated wastewater. Conventional wastewater treatments require a process consisting of several purification steps and need a disinfection phase to obtain microbiologically safe effluent aimed to irrigation. These disadvantages have prompted the scientific community to study new treatment systems able to guarantee the quality of treated water and the minimum environmental impact, in order to more easily meet water demand in agricultural sector.
Among the new systems recently proposed that can comply with this request, the SBBGR system, developed by the Water Research Institute (IRSA) of the Italian National Research Council (CNR), seems to be a promising technology. The aim of this study is the evaluation of SBBGR as a system able to increases the simplification of the treatment scheme for treating and reusing municipal raw wastewater and improves the management of water demand and supply.
In the present study, a larger group of physical, chemical and microbiological parameters was considered for evaluating the effectiveness of the SBBGR system for municipal wastewater treatment and agricultural reuse. SBBGR enhancement with sand filtration and chemical (by peracetic acid, PAA) or physical (by UV radiation) disinfection was also evaluated to have a high effluent quality needed for irrigation.
The monitored parameters were chosen according to the current Italian regulation and their representativeness. In particular, the microbial indicators were chosen considering that most human pathogens that could be derived from the reuse of wastewater belong to the domains of bacteria, viruses and protozoa, and these microorganisms are characterized by different physiological characteristics and consequently different survival rates in wastewater treatment. Furthermore the spreading of antibiotic resistent genes (ARGs) into the environment has recently raised a great concern for the risk of wastewater reuse as vehicle for genes, for this the removal SBBGR capability of four genes (ermB, sul1, sul2, tetA) resistant to different classes of antibiotics was evaluated in effluent after biological treatment and after tertiary phase.
The SBBGR resulted really efficient in removing suspended solids, COD, BOD and nitrogen with an average effluent concentration of 4, 40, 1 and 14 mg/L, respectively. Lower removal efficiency was observed for phosphorus with an average concentration in the effluent of 3.7 mg/L. Plant effluent was also characterized by an average electrical conductivity and sodium adsorption ratio of 0.88 mS/cm and 3.8, respectively. Therefore, according to these gross parameters, the SBBGR effluent was conformed to the national stand-ards required in Italy for agricultural reuse. Moreover, disinfection performances of the SBBGR was higher than that of conventional municipal wastewater treatment plants and met the quality criteria suggested by WHO (Escherichia coli <1000 CFU/100 mL) for agricultural reuse. In particular, the biological treatment by SBBGR removed, 2.5 ± 0.8 log units of total coliforms, 3.2 ± 1.1 log units of E. coli, 1.1 ± 0.4 log units of Clostridium perfringens, 1.4 ± 0.3 log units of Somatic coliphages, 1.5 ± 0.9 log units of Giardia and 1.8 ± 0.3 log units of Cryptosporidium. The investigated disinfection processes (UV and peracetic acid) resulted very effective for total coliforms, E. coli and somatic coliphages. In particular, a UV radiation and peracetic acid doses of 40 mJ/cm2 and 1 mg/L respectively reduced E. coli content in the effluent below the limit for agricultural reuse in Italy (10 CFU/100 mL). Conversely, they were both ineffective on C. perfringens spores.
The SBBGR system is able to reduce 1-2 logarithmic units of ARGs. In particular, a removal of 1.6 ± 0.7 log units was recorded for ermB, 1.9 ± 0.8 LUR for sul1 and 2.2 ± 1.1 for tetA, while for sul2 there was a lower decrease compared to the other genes, 1.0 ± 0.4. No reduction of the ARGs amount normalized to the total bacteria content (16S rDNA) was obtained, indicating that these genes are removed together with total bacteria and not specifically eliminated. Enhanced ARGs removal was obtained by sand filtration, while no reduction was achieved by both UV and PAA disinfection treatments tested
Advanced treatments for PFAS removal from landfill leachate: evaluating biological and ozone based chemical approaches
Full text linkIn the last decades, the rapid industrialization, the population growth and the urbanization led to the increase in waste generation. The practices of reuse, recycling, energy and matter recovery from waste are not sufficient to cope with this rise. Therefore, landfilling still remains a widely used practice. Within landfills, waste undergoes a number of physical, chemical and biological changes and releases micropollutants within the landfill leachate, making this matrix one of the most difficult to treat (Kumar et al., 2023).
Leachate is a complex mixture containing very high concentrations of biodegradable and recalcitrant toxic compounds (Qian et al., 2024). It contains a variety of micropollutants, such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), pharmaceuticals, personal care products, pesticides, microplastics (MPs), per- and polyfluoroalkyl substances (PFASs), and many more. Although micropollutants are present in very low concentrations they have significant impacts on the ecosystems, economy, human health.
The subject of this study are per- and polyfluoroalkyl substances, better known as PFAS, substances synthesized since the 1950s and entered the composition of a great many commercial products because of their outstanding hydro-, oleo-repellency and high stability characteristics. PFASare found in a wide range of products, from fertilizers to food packaging, from personal hygiene products to fire-fighting foams. These, at the end of their life cycle, sent to landfills release fluorinated substances into leachate, where the concentrations can reach up to thousands of μg/L (Gallen et al., 2017).
This study stems from the need to identify a solution for PFAS removal in landfill leachate and aims to evaluate the removal efficacy of PFAS and other key chemical parameters of two bench-scale treatment schemes: a biological treatment conducted in a Sequencing Batch Biofilter Granula Reactor (SBBGR) -and an ozone-enhanced biological treatment. Given the matrix complexity and the high chemical stability of PFAS, conventional treatments are inadequate for the removal of fluorinated substances. Hence the need to investigate an integrated approach combining biological degradation with chemical oxidation. Biological treatment was conducted in an SBBGR, an advanced biological treatment system, which is an upflow reactor in which leachate was fed, treated, and extracted sequentially. The plant operated in sequential mode with 8-hour treatment cycles. Each cycle featured a fill, reaction, and discharge phase. The chemical upgrading included an additional phase, the integration of biological degradation with chemical oxidation, performed with ozone at two different doses (4.0 g/L and 5.5 g/L). The discontinuity of the SBBGR system allowed oxidative treatment with ozone to be used in a specific and controlled manner. The ozonation step, following biological treatment, was specific for resistant biological degradation compounds. Ozone, dosed in a controlled manner, allowed for the partial oxidation of recalcitrant substances before returning them back to the biomass action.
The experimentation consisted of four phases: a start-up phase, a second phase with a steady state biological , a third phase in which biological treatment was enhanced with ozone at two different dosages, and a final phase in which reactor worked in biological mode fed with leachate at high PFAS concentration. During the preliminary start-up phase, an appropriate feeding program was used: gradual dilutions with water at decreasing ratios to acclimate the biomass to high salinity values (approximately 23 mS/cm) and to stimulate the growth of the species involved in the process.
The influent and effluent of all treatment schemes were characterized in terms of traditional parameters and PFAS. Per- and polyfluoroalkyl substances were analyzed by a mass spectrometer interfaced with very high-pressure liquid chromatography
The coronally advanced flap for the treatment of multiple recession defects: a modified surgical approach for the upper anterior teeth
No full textOBJECTIVE:
The aim of the study was to evaluate the clinical efficacy of a modification of the flap-design of the coronally advanced flap for the treatment of multiple gingival recessions affecting the anterior teeth in patients with aesthetic demands.
METHODS:
Six systemically and periodontally healthy subjects with multiple recession-type defects affecting the upper incisors and canines (recession depth < or = 2 mm) were enrolled in the study. All recessions fell into Miller class I or II. In each patient all present recessions were treated at the same surgical time with a modification of the coronally advanced flap technique. The clinical re-evaluation was made one year after the surgery.
RESULTS:
A total of 25 recessions (mean recession depth 2.84 +/- 1.0 mm) were treated. The mean number of gingival recessions treated in each subject was 4.1 (range 3 - 5). At the one-year examination, on average, 97% of the root surface was covered with soft tissue and 89% of the defects showed complete root coverage. Complete root coverage in all recessions was achieved in four out of the six (67%) treated patients. A statistically significant increase of keratinized tissue height (0.64 +/- 0.6 mm) was observed after one year.
CONCLUSIONS:
The frontal approach of the coronally advanced flap was effective for the treatment of multiple gingival recessions affecting the anterior teeth in patients with aesthetic demands, and these results were successful both in terms of root coverage and increase in keratinized tissue height
Modified two-stage procedures for the treatment of gingival recession
No full textBACKGROUND: Unfavorable conditions at the soft tissues adjacent to a recession defect may preclude performing pedicle flaps (advanced or rotational) both as a root coverage procedure, and as a covering flap for a connective tissue graft. Free gingival grafts may not be recommended because of the low root coverage predictability and the poor esthetic outcome. The goal of the present case report is to suggest modifications of the two-stage surgical technique aimed at improving root coverage and esthetic outcomes, and reducing patient morbidity.
METHOD: In the first case report, a Miller class II gingival recession, associated with a deep buccal probing depth, affecting a lower central incisor was treated. In the first step of the surgery an epithelized graft with an apical-coronal dimension equal to the keratinized tissue height of the adjacent teeth was sutured apical to the bone dehiscence. Four months later, a coronally advanced flap was performed to cover the root exposure. In the second case report, a Miller class III gingival recession, complicated with a deep buccal probing depth affecting the mesial root of the first lower molar was treated. In the first step of the surgery, a free gingival graft was positioned mesially to the root exposure to create keratinized tissue lateral to the recession defect. This was adequate to perform the laterally moved, coronally advanced flap that was used as a second-step root coverage surgical procedure.
RESULTS: In the first case report complete root coverage, an increase (4 mm) in keratinized tissue height and realignment of the mucogingival line were achieved 1 year after the surgery. The reduced dimension of the graft permitted to minimize patient's discomfort and to obtain good esthetics of mucogingival tissues. These successful outcomes were well maintained for 5 years. In the second case report successful root coverage, increase (3 mm) in keratinized tissue height and good harmony of mucogingival tissues were achieved 1 year after the surgery. These outcomes were well maintained 5 years after the surgery.
CONCLUSIONS: The present study suggested that modifications of the two-stage procedure by minimizing the dimension of the graft and by standardizing the surgical techniques allowed successful results to be achieved in the treatment of gingival recessions characterized by local conditions that otherwise preclude the use of one-step root coverage surgical techniques
Coronally advanced flap: a modified surgical approach for isolated recession-type defects: three-year results.
No full textVarious modifications of the coronally displaced flap have been proposed in the literature with the attempt of treating gingival recession with uneven predictable results. The goal of the present study was to evaluate the effectiveness with respect to root coverage of a modification of the coronally advanced flap procedure for the treatment of isolated recession-type defects in the upper jaw. Methods: Forty isolated gingival recessions with at least 1 mm of keratinized tissue apical to the defects were treated with a modified approach to the coronally advanced flap. The main change in the surgical procedure consisted in the modification of flap thickness and dimension of surgical papillae during flap elevation. All recessions fall into Miller class I or II. The clinical re-evaluation was performed 1 year and 3 years after the surgery. Results: At the 1-year examination, the average root coverage was 3.72 ± 1.0 mm (98.6% of the pre-operative recession depth) and 3.64 ± 1.1 mm (96.7%) at 3 years. The gain in probing attachment amounted to 3.65 ± 1.10 mm at 1 year and to 3.70 ± 1.09 mm at 3 years. The average increase of keratinized tissue between the baseline and the 3-year follow-up amounted to 1.78 ± 0.90 mm. All changes of keratinized tissue (difference between baseline and 1 year, baseline and 3 years, and between 1 and 3 years) were statistically significant. Conclusion: The modified coronally advanced surgical technique is effective in the treatment of isolated gingival recession in the upper ja
State of the Art and Innovative Communications and Networking Solutions for a Reliable and Efficient Interplanetary Internet
No full textRelativistic corrections to the Drell-Hearn-Gerasimov sum rule in the constituent quark model
No full textAbrasione cervicale corono-radicolare: trattamento combinato conservativo-parodontale. Case report
No full textPer molti anni il trattamento delle abrasioni cervicali è stato appannaggio esclusivo della terapia conservativa. Questa non può essere considerata una terapia di prima scelta quando l'abrasione interessa la superficie radicolare del dente, in quanto sia da un punto di vista biologico che estetico la radice dovrebbe e potrebbe essere ricoperta con i tessuti gengivali. In molti casi le abrasioni cervicali coinvolgono sia la corona che la radice anatomica del dente, motivo per cui la terapia ideale dovrebbe essere quella combinata conservativo-parodontale, la prima volta al ripristino dei tessuti duri coronali e la seconda finalizzata alla ricostruzione dei tessuti molli di copertura della radice. L'abrasione dei tessuti cervicali corono-radicolai comporta spesso l'eliminazione della giunzione amelo-cementizia rendendo difficoltosa la distinzione tra corona e radice anatomica. Inoltre non sempre e non tutta (recessioni di I e II classe di Miller in denti ruotati,estrusi o con perdita di altezza della/e papille o recessioni di III e IV classe ) la radice esposta è ricopribile con i tessuti molli. Queste limitazioni impongono di dover predeterminare la ricopertura radicolare, ovvero individuare la linea (cej clinica) in cui si posizionerà il margine gengivale dopo la guarigione di una chirurgia finalizzata alla ricopertura radicolare. Tale linea verrà utilizzata come limite apicale della preparazione del restauro conservativo che potrà così ripristinare la porzione più coronale della abrasione mentre alla chirurgia mucogengivale verrà dato il compito di ricoprire la recessione gengivale e la porzione più apicale della abrasione stessa.
Nel caso clinico trattato, la notevole profondità dell'abrasione e la sua estensione fino al margine gengivale apicale alla recessione, ha reso necessario il trattamento simultaneo conservativo-parodontale. Da un lato il primo approccio parodontale di incisione e scollamento del lembo ha permesso l'esposizione di un supporto radicolare, apicale all'abrasione, adeguato per il corretto isolamento del campo operatorio e dall'altro il trattamento conservativo ha consentito il posizionamento del margine coronale del lembo chirurgico al di sopra di una superficie coronale liscia e convessa
A novel surgical technique for soft tissue menagement in aesthetic areas of the mouth at implant placement. A case report.
No full textA new flap design, the multiple coronally advanced flap, ori- ginally designed for mucogingival surgery, is proposed for a different clinical indication: access flap for single implant insertion in areas of esthetic relevance.
Clinical features of multiple coronal advanced flap are the absence of a vertical releasing incisions, a variable thickness, combining areas of split and full thickness and the coronal repositioning of the flap
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