Achieving complete nitrification below the washout SRT with hybrid membrane aerated biofilm reactor (MABR) treating municipal wastewater

This study analyzed the performances of a hybrid membrane aerated biofilm reactor (MABR) pilot plant in terms of nutrients removal of the attached growth and suspended biomass in comparison with a conventional activated sludge (CAS) system at different sludge retention time (SRT) (20−3) days. Overall, the MABR showed better performances than the CAS in terms of TSS (86% vs 79%), COD (89% vs 85%) and total nitrogen (80% vs 65%). The minimum SRT for achieving complete nitrification in the MABR was close to 3 days, corresponding to a SRT in the aerobic compartment of 1.9 days, whereas in the CAS it was equal to 8 days (aerobic SRT of 4.8 days). Nitrification rate in biofilm was on average equal to 0.40 gNH4-N h−1 (2.40 gNH4-N m−2d−1). Its contribution to the overall nitrification in the MABR plant was 25–30% on average, although it increased when the SRT was decreased. Particle size distribution and microscopic analyses showed particles of biofilm detached from the membrane of the MABR. The seeding effect allowed sustaining nitrification of the suspend biomass at very low SRT. The nitrification rate observed in the suspended biomass in the MABR slightly decreased from 3.42 mgNH4-N gVSS−1 h−1 to 2.87 mgNH4-N gVSS−1 h−1 when the SRT was decreased from 20 days and 3 days, whereas in the CAS it collapsed from 2.33 mgNH4-N gVSS−1 h−1 to 0.47 mgNH4-N gVSS−1 h−1, because of nitrifying washout. Moreover, the biofilm detachment involved a positive effect in settling properties of the suspended biomass

Sequential biological and photocatalysis based treatments for shipboard slop purification: A pilot plant investigation

This study investigated the treatment of a shipboard slop containing commercial gasoline in a pilot plant scale consisting of a membrane biological reactor (MBR) and photocatalytic reactor (PCR) acting in series. The MBR contributed for approximately 70% to the overall slop purification. More precisely, the biological process was able to remove approximately 40%, on average, of the organic pollution in the slop. Nevertheless, the membrane was capable to retain a large amount of organic molecules within the system, amounting for a further 30% of the influent total organic content removal. However, this affected the membrane fouling, thus resulting in the increase of the pore blocking mechanism that accounted for approximately 20% to the total resistance to filtration (2.85∙10 13 m −1 ), even if a significant restoration of the original membrane permeability was obtained after chemical cleanings. On the other hand, the biological treatment produced a clear solution for the photocatalytic system, thereby optimizing the light penetration and generation of highly oxidizing active oxygen species that enabled the degradation of bio-recalcitrant compounds. Indeed, low total organic carbon (TOC) values (<10 mg L −1 ) were achieved in the output of the photocatalytic reactor by means of only 60 Einstein (E) of cumulative impinging energy after the addition of K 2 S 2 O 8 . Overall, coupling the two processes enabled very high TOC removal (ca. 95%)

Biomethane production from anaerobic co-digestion of selected organic fraction of municipal solid waste (Ofmsw) with sewage sludge: Effect of the inoculum to substrate ratio (isr) and mixture composition on process performances

The aim of this study was to evaluate the effect of the inoculum to substrate ratio (ISR) and the mixture ratio between organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) on the methane production potential achievable from anaerobic co-digestion (AcoD). Biochemical Methane Potential (BMP) assays at mesophilic temperature were used to determine the best AcoD configuration for maximizing methane yield and production rate, as well as to address possible synergistic effects. The maximum methane yield was observed at ISR of 1 and 60% OFMSW:40% SS as co-digestion mixture, whereas the highest methane production rate was achieved at ISR of 2 with the same mixture ratio (207 mL/gVS/d). Synergistic effects were highlighted in the mix-tures having OFMSW below 60%, determining an increase of approximately 40% in methane production than the OFMSW and SS digestion as a sole substrate. The experimental data demonstrated that co-digestion of OFMSW and SS resulted in an increase in the productivity of methane than anaerobic digestion using the sole substrates, producing higher yields or production rates while depending on the ISR and the mixture ratio

Desenvolupament d’un programari pel disseny de torres de rentat de gasos efluents contaminants

Aquest treball s’ha centrat principalment en el disseny d’un tipus de torres de rentat de gasos (scrubbers) com a sistemes de reducció d’emissions de contaminants en efluents de la indústria. Segons la Llei 34/2007 [14], s’estableixen les bases en matèria de prevenció, vigilància i reducció de la contaminació atmosfèrica amb la finalitat d’evitar, i quan no sigui possible, disminuir els danys que se’n puguin derivar a persones, medi ambient i altres bens de qualsevol naturalesa. L’objectiu principal ha sigut crear un programari (anomenat Scalc) que, a partir de paràmetres d’entrada (tipus de gas, cabal d’aire, composició, condicions d’operació, etc.) en pugui fer un disseny simplificat de la torre de rentat. A primera instància s’han fet les deduccions matemàtiques del comportament del sistema i s’han assumit un seguit de simplificacions a aplicar al disseny. S’han desenvolupat les equacions diferencials i models pertinents (correlacions de Sherwood, d’Onda i de Coulborn) per a arribar als resultats desitjats segons els models de disseny de reactors fluid-fluid. Seguidament, els resultats s’han validat amb exemples coneguts i finalment s’ha aplicat el programari (Scalc) a un cas d’estudi complert. Respecte als resultats, el càlcul i validació del diàmetre de la torre ha sigut el desitjat. Quant al càlcul de l’alçada de la torre en el cas d’absorció d’un compost químic sense reacció química, tot i que el comportament de les variables de sortida respecte a la variació de les d’entrada és satisfactori, existeixen certes discrepàncies en els resultats obtinguts segons el model diferencial aplicat i la correlació corresponent. Quant als càlculs pertinents a l’absorció amb reacció química, els resultats han estat satisfactoris, podent estimar l’alçada necessària del llit de rebliment per als casos estudiats ( on la cinètica de reacció es pot considerar molt ràpida)

Preliminary evaluation of biopolymers production by mixed microbial culture from citrus wastewater in a MBR system using respirometric techniques

This preliminary study was aimed at evaluating the feasibility to produce biopolymers (BP) from citrus wastewater by mixed microbial culture in an anaerobic/aerobic membrane bioreactor (A/O-MBR). The activated sludge of the A/O-MBR was successfully enriched in microorganisms having a good capacity in producing intracellular biopolymers. The production of BP was found to be about 0.55 mgCOD mgCOD−1 using pure acetate at a concentration of 1000 mgCOD L−1. When using fermented wastewater, the conversion of acetate into BP product was 0.56 mgCOD mgCOD−1 in the test performed with C/N equal to 1000:1, whereas it was only 0.12 mgCOD mgCOD−1 in the test with C/N of 100:5. The results achieved suggested the feasibility to use citrus wastewater as a feedstock for biopolymers production although the low biomass storage capacity (0.26 mgCOD mgCODbiomass−1) suggested the need for optimizing the operating conditions in future studies

Effect of biomass features on oxygen transfer in conventional activated sludge and membrane bioreactor systems

The aim of the present study was to compare the oxygen transfer efficiency in a conventional activated sludge and a membrane bioreactor system. The oxygen transfer was evaluated by means of the oxygen transfer coefficient (kLa)20 and α-factor calculation, under different total suspended solids concentration, extracellular polymeric substances, sludge apparent viscosity and size of the flocs. The (kLa)20 and α-factor showed an exponential decreasing trend with total suspended solid, with a stronger (kLa)20 dependence in the conventional activated sludge than the membrane bioreactor. It was noted that the (kLa)20 in the conventional activated sludge become comparable to that in membrane bioreactor when the TSS concentration in the conventional activated sludge was higher than 5 gTSS L-1. Operating under high carbon to nitrogen ratio, the (kLa)20 increased in both conventional activated sludge and membrane bioreactor because of the sludge deflocculation and a weaker dependence of (kLa)20 with total suspended solid was noted. The results indicated that the most important parameters on the oxygen transfer efficiency were in order: the total suspended solid concentration, flocs size, sludge apparent viscosity, the protein to polysaccharides ratio and extracellular polymeric substances content. Based on the influence of the main biomass features affecting the (kLa)20 and considering the typical operating conditions in both systems, those of membrane bioreactor appeared to be more favorable to oxygen transfer efficiency compared to conventional activated sludge process

Natural Product Nitric Oxide Chemistry: New Activity of Old Medicines

The use of complementary and alternative medicine (CAM) as a therapy and preventative care measure for cardiovascular diseases (CVD) may prove to be beneficial when used in conjunction with or in place of conventional medicine. However, the lack of understanding of a mechanism of action of many CAMs limits their use and acceptance in western medicine. We have recently recognized and characterized specific nitric oxide (NO) activity of select alternative and herbal medicines that may account for many of their reported health benefits. The ability of certain CAM to restore NO homeostasis both through enhancing endothelial production of NO and by providing a system for reducing nitrate and nitrite to NO as a compensatory pathway for repleting NO bioavailability may prove to be a safe and cost-effective strategy for combating CVD. We will review the current state of science behind NO activity of herbal medicines and their effects on CVD

Optimization of acetate production from citrus wastewater fermentation

Citrus wastewater is a sugar-rich waste stream suitable for the recovery of energy of material from its treatment. In this study, fermentation of citrus wastewater was carried out to assess the optimal conditions to maximize the bioconversion of the organic substrate into acetate. Unbalanced nutrient (C: N: P 200:0.1:0.1) enabled the highest acetate production. The presence of the particulate organic fraction enabled to obtain a higher acetate concentration regardless the initial COD concentration. Initial pH values higher than 5 did not cause substantial differences on the maximum bioconversion of COD into acetate, whereas pH lower than 5 hindered the hydrolysis process. Lastly, the bioconversion rate of the organic substrate into acetate decreased from a maximum of 23% to a minimum of 8% related to the initial COD. The achieved results demonstrated that the characteristics of citrus wastewater enable its valorisation without the need to apply energy-consuming processes

Comparison between two MBR pilot plants treating synthetic shipboard slops: the effect of salinity increase on biological performance, biomass activity and fouling tendency

The paper reports the main results of an experimental campaign carried out on two bench scale pilot plants for the treatment of synthetic shipboard slops. In particular, two membrane bioreactors (MBRs) with submerged configuration were analyzed. One MBR pilot plant (namely, Line A) was fed with synthetic shipboard slop and was subjected to a gradual increase of salinity. Conversely, the second MBR pilot plant (namely, Line B) was fed with the same synthetic shipboard slop but without salt addition, therefore operating as a \ue2\u80\u9ccontrol\ue2\u80\u9d unit. Organic carbon, hydrocarbons and ammonium removal, kinetic constants, extracellular polymeric substances (EPSs) production and membranes fouling rates have been assessed. The observed results highlighted a stress effect exerted by salinity on the biological performances, with lower removal efficiencies in the Line A compared to Line B. Significant releases of soluble EPS in Line A promoted an increase of the resistance related to particle deposition into membrane pores (pore fouling tendency), likely due to a worsening of the mixed liquor features. Such a condition enhanced the reduction of the \ue2\u80\u9cpre-filter\ue2\u80\u9d effect of the cake layer

Epidemiology of intensive care unit-acquired sepsis in Italy: results of the SPIN-UTI network

BACKGROUND: Sepsis is the major cause of mortality from any infectious disease worldwide. Sepsis may be the result of a healthcare associated infection (HAI): the most frequent adverse events during care delivery especially in Intensive Care Units (ICUs). The main aim of the present study was to describe the epidemiology of ICU-acquired sepsis and related outcomes among patients enrolled in the framework of the Italian Nosocomial Infections Surveillance in ICUs - SPIN-UTI project. STUDY DESIGN: Prospective multicenter study. METHODS: The SPIN-UTI network adopted the European protocols for patient-based HAI surveillance. RESULTS: During the five editions of the SPIN-UTI project, from 2008 to 2017, 47.0% of HAIs has led to sepsis in 832 patients. Overall, 57.0% episodes were classified as sepsis, 20.5% as severe sepsis and 22.5% as septic shock. The most common isolated microorganisms from sepsis episodes were Acinetobacter baumannii, Klebsiella pneumoniae and Pseudomonas aeruginosa. The case fatality rate increased with the severity of sepsis and the mean length of ICU-stay was significantly higher in patients with ICU-acquired sepsis than in patients without. CONCLUSION: Our study provides evidence that ICU-acquired sepsis occurs frequently in Italian ICU patients and is associated with a high case fatality rate and increased length of stay. However, in order to explain these findings further analyses are needed in this population of ICU patient