Phosphorus recovery from a pilot-scale grate furnace: influencing factors beyond wet chemical leaching conditions.

Phosphorus is a non-renewable resource going to be exhausted in the future. Sewage sludge ash is a promising secondary raw material due to its high phosphorus content. In this work, the distribution of 19 elements in bottom and cyclone ashes from pilot-scale grate furnace have been monitored to determine the suitability for the phosphorus acid extraction. Moreover, the influence of some parameters beyond wet chemical leaching conditions were investigated. Experimental results showed that bottom ash presented lower contamination in comparison to cyclone ash and low co-dissolution of heavy metals (especially Cr, Pb and Ni), while high phosphorus extraction efficiencies (76-86%) were achieved. High Al content in the bottom ash (9.4%) negatively affected the phosphorus extraction efficiency as well as loss on ignition, while the particle size reduction was necessary for ensuring a suitable contact surface. The typology of precipitating agents did not strongly affect the phosphorus precipitation, while pH was the key parameter. At pH 3.5-5, phosphorus precipitation efficiencies higher than 90% were achieved, with a mean phosphorus content in the recovered material equal to 16-17%, comparable to commercial fertilizers. Instead, the co-precipitation of Fe and Al had a detrimental effect on the recovered material, indicating the need for additional treatments.

Metal-based flocculation to harvest microalgae: a look beyond separation efficiency.

Metal-based flocculants are commonly used for biomass harvesting in microalgae-based bio-refineries. Besides the high separation efficiency, additional aspects should be considered, related to the toxicity of metals for the algal biomass. Partitioning tests for commonly used flocculants (i.e., FeCl3 and Al2(SO4)3) showed that metals were mostly transferred to the solid phase with more than 95% of dosed metal ending up into the biomass, and low metal concentrations in the liquid effluent (lower than 0.4 mg L-1 for both metals), thus allowing for water reuse. Photosynthesis inhibition was tested on microalgae and microalgae-bacteria cultures, using a standardized photo-respirometry protocol in which typical concentrations used during coagulation-flocculation were assessed. Modelling dose-response curves, concentrations corresponding to 50% inhibition (IC50) were obtained, describing short-term effects. The obtained IC50 ranged from 13.7 to 28.3 mg Al L-1 for Al, and from 127.9 to 195.8 mg Fe L-1 for Fe, showing a higher toxicity for the Al-based flocculant. The recovery of photosynthesis inhibition was also quantified, to evaluate the possibility of reusing/recycling the harvested biomass. The results highlighted that the residual photosynthetic activities, evaluated after 1 h and 24 h of exposure to metals were partially recovered, especially for Al, passing from 67.3% to 94.6% activity, respectively, while long-term Fe effects were stronger (passing from 64.9% to 77.6% activity). A non-toxic flocculant (cationic starch) was finally tested, excluding potential effects due to biomass aggregation, as the reduction of photosynthetic activity only reached 3.4%, compared to control. Relevant modifications to the light availability and the optical properties of algal suspensions were assessed, identifying a strong effect of iron which caused an increase of the light absorbance up to approximately 40% at high Fe concentrations. Possible implications of dosing metallic flocculants in MBWWT processes are discussed, and suggestions are given to perform inhibition tests on flocculating chemicals.

Autotrophic nitrogen removal by a two-step SBR process applied to mixed agro-digestate.

The aim of this research was to evaluate the applicability of partial-nitritation/anammox processes for biological N removal from a centrifuge supernatant coming from a full scale anaerobic digester fed on a mixture of piggery manure, poultry manure, and agro-wastes. Stable partial nitritation was achieved at pilot-scale (650L SBR), obtaining a suitable influent for the anammox lab-scale SBR reactor (3L). The anammox lab scale reactor was fed with increasing fractions of the partial nitritation effluent, blended with synthetic wastewater. In the last 100days no dilution was used. The nitrogen loading rate applied to the anammox reactor was 0.5-0.6gNL(-)(1)d(-)(1) and the average nitrogen removal was 91±10%. During the first days of operation with undiluted supernatant, the maximum anammox activity in the SBR decreased, but recovered afterwards, suggesting the ability of the anammox biomass to acclimate to the wastewater. N2O emissions in both reactors were also measured.

Low temperature microwave and conventional heating pre-treatments to improve sludge anaerobic biodegradability.

This paper presents the results of lab-scale experiments on low temperature thermal pre-treatment (less than 100 °C) prior to anaerobic digestion of sewage sludge. Two heating ways, microwave heating (MH) and conventional heating (CH), and two types of sludge, primary and waste activated sludge, were compared under the same experimental conditions. The degree of solubilisation produced by MH and CH up to 72, 82 and 93 °C was firstly estimated. For both types of heating, increase in soluble chemical oxygen demand (COD) caused by the pre-treatment was about 14% on waste activated sludge and only 3% on primary sludge. The final temperature of 72 °C resulted as the most cost-effective in terms of additional soluble COD per unit of energy required. Subsequently, five series of biochemical methane potential mesophilic assays were run in 120 mL serum bottles on sludge samples pre-treated at 72 °C. When compared with control reaction vessels, no significant differences were noticed in net methane production of pre-treated primary sludge, whereas a relevant increase occurred regarding the pre-treated waste activated sludge. It was also observed that the trend of methane content in biogas during the batch tests can be described by a second order polynomial.

Long-term effects of the ozonation of the sludge recycling stream on excess sludge reduction and biomass activity at full-scale.

This paper presents a full-scale experience of sludge minimization by means of short contact time ozonation in a wastewater treatment plant (WWTP) mainly fed on textile wastewater. The WWTP performance over a 3-year operational data series was analysed and compared with a two-year operation with sludge ozonation. Lab-scale respirometric tests were also performed to characterize biomass activity upstream and downstream of the ozone contact reactor. Results suggest that sludge ozonation: (1) is capable of decreasing excess sludge production by 17%; (2) partially decreases both N removal, by lowering the denitrification capacity, and P removal, by reducing biomass synthesis; (3) increases the decay rate from the typical value of 0.62 d(-1) to 1.3 d(-1); (4) decreases the heterotrophic growth yield from the typical value of 0.67 to 0.58 gCOD/gCOD.

Temperature modelling and prediction for activated sludge systems.

Temperature is an important factor affecting biomass activity, which is critical to maintain efficient biological wastewater treatment, and also physiochemical properties of mixed liquor as dissolved oxygen saturation and settling velocity. Controlling temperature is not normally possible for treatment systems but incorporating factors impacting temperature in the design process, such as aeration system, surface to volume ratio, and tank geometry can reduce the range of temperature extremes and improve the overall process performance. Determining how much these design or up-grade options affect the tank temperature requires a temperature model that can be used with existing design methodologies. This paper presents a new steady state temperature model developed by incorporating the best aspects of previously published models, introducing new functions for selected heat exchange paths and improving the method for predicting the effects of covering aeration tanks. Numerical improvements with embedded reference data provide simpler formulation, faster execution, easier sensitivity analyses, using an ordinary spreadsheet. The paper presents several cases to validate the model.

Automatic set-point titration for monitoring nitrification in SBRs.

Nitrification is usually the bottleneck of biological nitrogen removal processes. In SBRs systems, it is not often enough to monitor dissolved oxygen, pH and ORP to spot problems which may occur in nitrification processes. Therefore, automated supervision systems should be designed to include the possibility of monitoring the activity of nitrifying populations. Though the applicability of set-point titration for monitoring biological processes has been widely demonstrated in the literature, the possibility of an automated procedure is still at its early stage of industrial development. In this work, the use of an at-line automated titrator named TITAAN (TITrimetric Automated ANalyser) is presented. The completely automated sensor enables us to track nitrification rate trend with time in an SBR, detecting the causes leading to slower specific nitrification rates. It was also possible to perform early detection of toxic compounds in the influent by assessing their effect on the nitrifying biomass. Nitrifications rates were determined with average errors+/-10% (on 26 tests), never exceeding 20% as compared with UV-spectrophotometric determinations.

Autotrophic nitrogen removal from anaerobic supernatant of Florence's WWTP digesters.

In municipal WWTP with anaerobic sludge digestion, 10-20% of total nitrogen load comes from the return supernatant produced by the final sludge dewatering. In recent years a completely autotrophic nitrogen removal process based on Anammox biomass has been tested in a few European countries, in order to treat anaerobic supernatant and to increase the COD/N ratio in municipal wastewater. This work reports the experimental results of the SHARON-ANAMMOX process application to anaerobic supernatant taken from the urban Florentine area wastewater treatment plant (S. Colombano WWTP). A nitritation labscale chemostat (7.4 L) has been started-up seeded with the S. Colombano WWTP nitrifying activated sludge. During the experimental period, nitrite oxidising bacteria wash-out was steadily achieved with a retention time ranging from 1 to 1.5 d at 35 degrees C. The Anammox inoculum sludge was taken from a pilot plant at EAWAG (Zurich). Anammox biomass has been enriched at 33 degrees C with anaerobic supernatant diluted with sodium nitrite solution until reaching a maximum specific nitrogen removal rate of 0.065 kgN kg(-1) VSS d(-1), which was 11 times higher than the one found in inoculum sludge (0.005 kgN kg(-1) VSS d(-1). In a lab-scale SBR reactor (4 L), coupled with nitritation bioreactor, specific nitrogen removal rate (doubling time equal to 26 d at 35 degrees C and at nitrite-limiting condition) reached the value of 0.22 kgN kg(-1) VSS d(-1), which was approximately 44 times larger than the rate measured in the inoculum Anammox sludge.

SBR on-line monitoring by set-point titration.

The applicability of set-point titration for monitoring biological processes has been widely demonstrated in the literature. Based on published and on-going experiences, some operating procedures have been specifically developed to be applied to SBRs, so that real-time information about the process and/or the influent can be obtained. This, in turn, would allow plant operators to select the most appropriate actions properly and timely. Five operating modes are described for the monitoring of (1) influent toxicity, (2) influent N-content, (3) nitrification capacity, (4) end of the nitrification reaction, and (5) nitrate effluent concentration, and are currently tested on the on-line titrator TITAAN (TITrimetric Automated ANalyser) which is in operation on a pilot scale SBR.

Upgrading of Florence wastewater treatment plant: co-digestion and nitrogen autotrophic removal.

In recent years a completely autotrophic nitrogen removal process based on Anammox biomass has been tested in a few European countries in order to treat anaerobic supernatant and to increase the COD/N ratio in municipal wastewater. This work reports experimental results on a possible technical solution to upgrade the S. Colombano treatment plant which treats wastewater from the Florentine urban area. The idea is to use 50% of the volume of the anaerobic digester in order to treat external sewage sludge (as septic tank sludge) together with waste activated sludge and to treat the resulting effluent on a SHARON-ANAMMOX process in order to remove nitrogen from the anaerobic supernatant. Anaerobic co-digestion, tested in a 200 L pilot plant, enables low cost treatment of septic tank sludge and increases biogas production; however, it also increases the nitrogen load re-circulated to the WWTP, where nitrogen removal efficiency is already low (<50%), due to the low COD/N ratio, which limits predenitrification efficiency. Experimental results from a SHARON process tested in a lab-scale pilot plant show that nitrite oxidising bacteria are washed-out and steady nitrite production can be achieved at retention times in the range 1 - 1.5 days, at 35 degrees C. In a lab-scale SBR reactor, coupled with a nitration bioreactor, maximum specific nitrogen removal rate under nitrite-limiting conditions (with doubling time equal to about 26 days at 35 degrees C) was equal to 0.22 kgN/kgSSV/d, about 44 times the rate measured in inoculum Anammox sludge. Finally, a cost analysis of the proposed upgrade is reported.

Left ventricular hemangioma.

Cardiac hemangiomas are rare, primary benign cardiac tumors. The authors report their experience of diagnosis and treatment of an hemangioma localized into the left ventricle. The tumor could be successfully resected and there is no recurrence at 1 year follow-up.

[High-resolution electrocardiography evaluation of late potentials. A comparison between Frank XYZ orthogonal leads and standard precordial electrocardiographic leads]. / Determinazione mediante elettrocardiografia ad alta risoluzione dei potenziali tardivi. Confronto fra le derivazioni ortogonali XYZ di Frank e le derivazioni elettrocardiografiche precordiali standard.

High-resolution electrocardiography has been used as a non-invasive method for the study of delayed potentials in order to evaluate the risk of the onset of ventricular arrhythmia first in ischaemic cardiopathy and then in various cardiopathies, generally using XYZ orthogonal derivations. The aim of this study was to compare the results obtained with those using standard precordial leads, in particular V4 and V6 leads. A group of 28 patients, males and females, aged between 15 and 55 years of age, was examined. All patients were suffering from different cardiopathies. Subjects with delayed right and left ventricular activation on the surface ECG tracing were excluded from the study. A 60-200 Hertz bandpass filter and time averaging of 300 consecutive complexes were used to analyse tracings. Dual recordings were performed for each patient. The following parameters were examined: total duration of filtered QRS complex and root-mean-square voltage of potentials in the last 40 msec of filtered QRS (RMS). In particular, the comparison between RMS using Frank's method and those obtained using V4 and V6 precordial leads provided a coefficient of correlation of r = 0.91 with p < 0.001 and r = 0.92 with p < 0.001 respectively, and the comparison between QRS obtained using the same method and that obtained using V4-V6 precordial leads gave a coefficient of correlation of R = 0.80, p < 0.001 and r = 0.77 and p < 0.001 respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

[Echocardiographic changes in patients with polycystic nephropathy]. / Alterazioni ecocardiografiche in pazienti affetti da nefropatia policistica.

We have studied with the echocardiography M-Mode, 2-D, Doppler three groups of 15 subjects for testing the presence of cardiac abnormalities probably related to primary collagen defect in patients with autosomal dominant polycystic kidney disease (ADPKD) The first group was made up of patients with ADPKD and normal renal function, the second of patients with ADPKD in hemodialysis (HD), the last one of patients in HD for other renal disease. In the first group we found no cardiovascular abnormalities while we found an increased incidence of valvular disease (p = 0.016) in patients with ADPKD in HD and an increased incidence in valvular disease (p = 0.016) and left atrial dilatation (p = 0.006) in patients in HD for different renal disease. When we estimated the cases on the ground of dialytic age uncorrelated with the initial renal disease, only the incidence of valvular calcifications was increased in patients on HD more than 3 years (p = 0.034). In our group of patients the echocardiographic abnormalities seem to be related more to uremic cardiomyopathy even if we cannot deny the existence of primary cardiac disease in patients with ADPKD.

[Late potentials in patients with prolapse of the mitral valve]. / Studio dei potenziali tardivi in pazienti con prolasso della valvola mitrale.

Recently published reports have highlighted the presence of a high incidence of late potentials in patients with mitral valve prolapse. In order to verify this observation 29 patients suffering from this pathology were studied using high-resolution electrocardiography. Late potentials were present in 24% of patients with mitral valve prolapse in comparison to 5% of control subjects (p less than 0.05); no correlation was found however in patients with mitral valve prolapse between the presence of late potentials and Holter's ventricular hyperkinetic tachycardia. At a follow-up after 16 +/- 4 months no patient presented persistent ventricular tachycardia or sudden death. The presence of late potentials might be yet symptom of the mitral prolapse syndrome whose prognostic role, although not yet clear, does not appear to represent a negative factor in relation to major tachycardia attacks.

[A case of rupture of the tendinous cord caused by infective endocarditis]. / Considerazioni su un caso di rottura di corda tendinea da endocardite infettiva.

The paper reports a case of infective endocarditis of the valve, with an insidious and slow onset accompanied by low fever, debility, loss of weight, anemia, and the concomitant echocardiographic observation of pericardial effusion. Subsequent echocardiographic tests produced images which probably referred to valvular vegetation. As a matter of fact these findings proved to be result of the rupture of the latero-posterior tendinous cord of the mitral flap and other similar cords whose stumps, covered in fibrin, had adhered to the edge of the anterior cups. This finding was discovered during surgery, which was performed early and successfully, and was followed by excellent long-term results.

Evaluation of noninvasive alternatives to right heart catheterization.

We mechanocardiographically evaluated 50 patients with acute myocardial infarction, invasively monitored by Swan-Ganz catheters, in order to assess if mechanocardiography could provide reliable hemodynamic informations. The last 25 subjects were also studied by pulsed Doppler echocardiography. Our results confirm the high precision of apexcardiography in assessing mean pulmonary capillary wedge pressure (r = 0.91) while Doppler echocardiography proved itself better than mechanocardiography in assessing cardiac output (r = 0.82 vs r = 0.78). Moreover, Doppler echocardiography allowed a good estimation of mean pulmonary artery pressure (r = 0.81) which cannot be assessed by other noninvasive methods. However, we could not find any clinically useful relationship between Doppler mitralic flow characteristics and mean pulmonary capillary wedge pressure. Therefore noninvasive methods could represent a valid alternative to right heart catheterization provided that an integrated Doppler echocardiographic and mechanocardiographic approach is used.

[Evaluation of different electrocardiographic scores (QRS score) for estimating the ejection fraction of the left ventricle after acute myocardial infarct]. / Valutazione di differenti punteggi elettrocardiografici (QRS score) per la stima della frazione d'eiezione ventricolare sinistra dopo infarto miocardico acuto.

We calculated the QRS score using both the simplified Selvester's method and the Hills' one, extended to the 12 standard leads, from the electrocardiograms registered on the fifth and thirtieth day from the ischemic event from 50 infarcted patients whose radionuclide left ventricular ejection fraction was known. The analysis of our results showed a very good correlation existing between the early and the late scores (r = 0.91 Hillis's method) as well as the equivalence of the two methods as witnessed by a correlation coefficient of 0.86 on the fifth day electrocardiogram and of 0.84 on the thirtieth day E.C.G. However the correlation between QRS score and left ventricular ejection fraction was quite weak ranging from -0.36 to -0.48 depending upon the method and the moment selected for the acquisition of the data. Even the attempt to correctly select patients with a higher risk identifying a QRS score able to predict a reduced left ventricular ejection fraction (i.e. less than 40%) failed because of the low sensitivity and specificity of the method. We therefore believe that the QRS score or, at least the simplified one, is not useful to assess the residual left ventricular function after a myocardial infarction and its use should be reduced to the evaluation of the infarct size.

[Electrocardiographic finding of Osborn's J wave in patients with hypothermia. Description of 2 clinical cases]. / Riscontro elettrocardiografico dell'onda J di Osborn in pazienti affetti da ipotermia. Descrizione di due casi clinici.

Two cases of hypothermia in the elderly are described. The different clinical evolution shows how the concurrent presence of Diabetes Mellitus can be considered as an adverse prognostic factor. It is also confirmed that the Osborn's wave electrocardiographic presence, given up a specific and pathognomonic diagnostic parameter in this disease. The observation that the electrocardiographic J wave can regress after body's temperature normalization suggests the hypothesis that this wave reflects reversible delay of depolarization, or early repolarization.