Wastewater treatment with particulate biofilm reactors.

The review presented in this paper focuses on applications of particulate biofilm reactors (e.g. Upflow Sludge Blanket, Biofilm Fluidized Bed, Expanded Granular Sludge Blanket, Biofilm Airlift Suspension, Internal Circulation reactors). Several full-scale applications for municipal and industrial wastewater treatment are presented and illustrated, and their most important design and operation aspects (e.g. biofilm formation, hydrodynamics, mass transfer, mixing) are analysed and discussed. It is clear from the review that this technology can be considered a grown up technology for which good design and scale-up guidelines are available.

Particle-based biofilm reactor technology.

Particle-based biofilm reactors provide the potential to develop compact and high-rate processes. In these reactors, a large biomass content can be maintained (up to 30 g l-1), and the large specific surface area (up to 3000 m2 m-3) ensures that the conversions are not strongly limited by the biofilm liquid mass-transfer rate. Engineered design and control of particle-based biofilm reactors are established, and reliable correlations exist for the estimation of the design parameters. As a result, a new generation of high-load, efficient biofilm reactors are operating throughout the world with several full-scale applications for industrial and municipal waste-water treatment.

Genetic polymorphism of the renin-angiotensin system and organ damage in essential hypertension.

BACKGROUND: The renin-angiotensin-aldosterone system (RAAS) plays a significant role in the development of hypertensive cardiac and vascular remodeling. Recently, several genetic variants of its key components, which may be clinically relevant and thus prove to be useful in the evaluation of cardiovascular risk, have been described. We therefore investigated the association between ACE I/D, AGT M235T, and AT1 A1266C gene polymorphisms and early signs of target organ damage in 215 untreated patients with essential hypertension (EH). METHODS: Genotyping was based on the polymerase chain reaction technique, with further restriction analysis when required. Albuminuria was measured as the albumin-to-creatinine ratio (ACR). The left ventricular mass index (LVMI) was assessed by echocardiography (LVH = LVMI > or = 125 g/m2), carotid wall thickness (IMT) by an ultrasonographic (US) scan, and retinal vascular changes by direct ophthalmoscopy (Keith-Wagener classification). RESULTS: The prevalence of microalbuminuria (Mi), LVH, and retinal vascular changes was 14, 46, and 74%, respectively. ACE, AGT, and AT1 genotype distribution was in agreement with the Hardy-Weinberg equilibrium. There was no difference in age, duration of disease, body mass index (BMI), blood pressure, and lipid profile when data were analyzed on the basis of genotype. Serum levels of angiotensin-converting enzyme (ACE) were related to the ACE genotype (10.2 +/- 0.5, DD; 8.2 +/- 0.3, ID; 6.5 +/- 0.4 IU/mL, II; P < 0. 0001 by analysis of variance). The ACE genotype independently influences serum ACE levels and accounts for approximately 14% of its variations (F = 26.7, r2 = 0.1393, df 1 to 214, P < 0.0001). Patients with DD and ID genotypes showed higher levels of ACR (1.59 +/- 0.2, DD + ID; 0.8 +/- 0.2 mg/mmol, II; P < 0.006 by ANOVA) and bigger LVMI (124.1 +/- 2.3, DD + ID vs. 117.8 +/- 3.6 g/m2, II; P < 0.01 by ANOVA). No differences in the prevalence and degree of target organ damage (TOD) were found when data were analyzed on the basis of the AGT and AT1 genotypes, respectively. Potentially unfavorable combinations of genotypes were also investigated by K-means cluster analysis. Two subgroups of patients were identified (cluster 1, N = 70; cluster 2, N = 57), and each differed significantly with regards to the presence and degree of TOD and patterns of RAAS gene polymorphisms (F, 15.97 for ACR; F, 7.19 for IMT; F, 217.03 for LVMI; F, 3.91 for ACE; F, 4.06 for AGT; and F, 5. 22 for AT1; df 1 to 214, P < 0.02, for each one of the variables examined). CONCLUSION: The D allele of the ACE gene may be an independent risk factor for the development of target organ damage, and evaluating it could be useful for assessing cardiovascular risk in EH. Unfavorable patterns of RAAS genotypes seem to predispose patients to subclinical cardiovascular disease in EH.

Left ventricular geometry and function in patients with essential hypertension and microalbuminuria.

BACKGROUND: Microalbuminuria has recently emerged as a strong, independent predictor of cardiovascular mortality in patients with essential hypertension, yet the pathophysiological mechanisms underlying this association remain to be elucidated. OBJECTIVE: To study the relationship between microalbuminuria and left ventricular geometry and function and extra-cardiac vascular changes in a group of 211 untreated hypertensive patients. METHODS: Albuminuria was evaluated as albumin-to-creatinine ratio in three non-consecutive first morning urine samples. Left ventricular mass index and function were assessed by M-B mode echocardiography and carotid wall thickness by high-resolution ultrasound scan. RESULTS: The prevalences of microalbuminuria and left ventricular hypertrophy were 14 and 47% respectively. Patients in the top quartile of albuminuria showed a higher left ventricular mass index (57 +/- 1.8, 55 +/- 2, 47 +/- 1.4 and 48 +/- 1.6 g/m2.7, respectively; P< 0.0001) as well as a higher prevalence of left ventricular hypertrophy (72, 65, 26 and 25%, respectively; P< 0.001) and especially concentric hypertrophy (56, 47, 17 and 21%, respectively; P< 0.0001) in the four quartiles of albuminuria. Microalbuminuric patients showed depressed left ventricular performance as indicated by a reduced midwall fractional shortening (15.7 +/- 0.3, 15.9 +/- 0.3, 16.7 +/- 0.4 and 16.8 +/- 0.3%, respectively; P< 0.02). Furthermore patients in the top quartile of albuminuria showed increased carotid wall thickness as compared to normoalbuminuric patients (0.78 +/- 0.03, 0.7 +/- 0.04, 0.65 +/- 0.03 and 0.6 +/- 0.03 mm, respectively; P < 0.001). CONCLUSIONS: Hypertensive patients with microalbuminuria show a higher prevalence of unfavourable left ventricular geometric patterns, depressed left ventricular function and early signs of extra-cardiac vascular damage. These findings strengthen the role of microalbuminuria as an indicator of subclinical cardiovascular disease and may account for the worse outcome that is usually associated with increased urinary albumin excretion in essential hypertension.

Terminal settling velocity and bed-expansion characteristics of biofilm-coated particles.

Fluid dynamic behavior of biofilm-coated particles in ambient water has been investigated. New experimental results are presented and compared with published data. From experimental measurements of the single particle terminal settling velocity the corresponding drag coefficient was found to be larger (by a factor of 1.6) than that for a smooth, rigid sphere at the same Reynolds number. A new simple correlation describing this finding is suggested. For multiparticle systems the Richardson-Zaki equation, derived empirically for rigid particles, provided a satisfactory description of biological beds. Of the two numerical parameters characterizing the expansion law, i. e. the slope n and the extrapolation to voidage equal one ui, the first was found to be similar to that suggested by Richardson and Zaki (1954), whereas ui gave results smaller than the single-particle terminal settling velocity, in contrast with the mentioned work but in agreement with more recently published behavior.

Increased renal resistive index in patients with essential hypertension: a marker of target organ damage.

BACKGROUND: Increased renal resistance detected by ultrasound (US) Doppler has been reported in severe essential hypertension (EH) and recently was shown to correlate with the degree of renal impairment in hypertensive patients with chronic renal failure. However, the pathophysiological significance of this finding is still controversial. METHODS: In a group of 211 untreated patients with EH, we evaluated renal resistive index (RI) by US Doppler of interlobar arteries and early signs of target organ damage (TOD). Albuminuria was measured as the albumin to creatinine ratio (ACR) in three non-consecutive first morning urine samples. Left ventricular mass was evaluated by M-B mode echocardiography, and carotid wall thickness (IMT) by high resolution US scan. RESULTS: RI was positively correlated with age (r=0.25, P=0.003) and systolic blood pressure (SBP) (r=0.2, P=0.02) and with signs of early TOD, namely ACR (r=0.22, P=0.01) and IMT (r=0.17, P<0.05), and inversely correlated with renal volume (r=-0.22, P=0.01) and diastolic blood pressure (r=-0.23, P=0.006). Multiple linear regression analysis demonstrated that age, gender, ACR and SBP independently influence RI and together account for approximately 20% of its variations (F=8.153, P<0.0001). When clinical data were analysed according to the degree of RI, the patients in the top quartile were found to be older (P<0.05) and with higher SBP (P<0.05) as well as early signs of TOD, namely increased ACR (P<0.002) and IMT (P<0.005 by ANOVA), despite similar body mass index, uric acid, fasting blood glucose, lipid profile and duration of hypertension. Furthermore, patients with higher RI showed a significantly higher prevalence of microalbuminuria (13 vs 12 vs 3 vs 33% chi2=11.72, P=0.008) and left ventricular hypertrophy (40 vs 43 vs 32 vs 60%, chi2=9.25, P<0.05). CONCLUSIONS: Increased RI is associated with early signs of TOD in EH and could be a marker of intrarenal atherosclerosis.

Microalbuminuria is an early marker of target organ damage in essential hypertension.

Microalbuminuria has been associated with a cluster of metabolic and nonmetabolic risk factors, suggesting that it might indicate the presence of generalized microvascular damage in patients with essential hypertension. To explore whether microalbuminuria is associated with early target organ damage, two groups of essential hypertensive patients, with (n = 17) (HtAlb+) and without (n = 16) (HtAlb-) microalbuminuria, and a control group (C) of healthy normotensive subjects (n = 20) were studied. The study groups, selected among participants of a large epidemiologic trial, were carefully matched for several potentially confounding variables such as gender, age, duration of hypertension, and body mass index. Albumin excretion rate was evaluated by radioimmunoassay in three nonconsecutive timed overnight collections after 3 weeks of pharmacologic wash-out. Left ventricular mass was assessed by M-B-mode echocardiography, carotid wall thickness by a high resolution ultrasound scan, and renal vascular impedance by Doppler scan. Office as well as 24-h ambulatory pressure monitoring (Takeda TM-2420) were also evaluated. There was no difference between the two hypertensive groups for office and 24-h blood pressure levels except for a lower daytime/nighttime systolic blood pressure ratio in the group with microalbuminuria. Microalbuminuric patients showed signs of early organ damage as compared to normoalbuminuric patients and normal subjects, namely greater left ventricular mass indices (LVMI 167+/-7 g/m2 in HtAlb+; 139+/-9 g/m2 in HtAlb-; 118+/-5 g/m2 in C, P < .001) and increased wall thickness of common carotid arteries (intima plus media thickness 12.5+/-0.2 mm in HtAlb+; 11.7+/-0.3 mm in HtAlb-; 11.2+/-0.2 mm in C, P < .001) as well as higher intrarenal vascular resistance (mean resistive index 0.62+/-0.01 in HtAlb+; 0.59+/-0.01 in HtAlb-; 0.59+/-0.01 in C, P < .05). In conclusion, microalbuminuria is an early marker of diffuse target organ damage in essential hypertension and therefore can be useful to identify patients for whom more aggressive preventive strategies or additional treatment measures are advisable.

Hydrodynamic characteristics and gas-liquid mass transfer in a biofilm airlift suspension reactor.

The hydrodynamics and mass transfer, specifically the effects of gas velocity and the presence and type of solids on the gas hold-up and volumetric mass transfer coefficient, were studied on a lab-scale airlift reactor with internal draft tube. Basalt particles and biofilm-coated particles were used as solid phase. Three distinct flow regimes were observed with increasing gas flow rate. The influence of the solid phase on the hydrodynamics was a peculiar characteristic of the regimes. The volumetric mass transfer coefficient was found to decrease with increasing solid loading and particle size. This could be predominantly related to the influence that the solid has on gas hold-up. The ratio between gas hold-up and volumetric mass transfer coefficient was found to be independent of solid loading, size, or density, and it was proven that the presence of solids in airlift reactors lowers the number of gas bubbles without changing their size. To evaluate scale effects, experimental results were compared with theoretical and empirical models proposed for similar systems.

Prevalence and clinical correlates of microalbuminuria in essential hypertension: the MAGIC Study. Microalbuminuria: A Genoa Investigation on Complications.

The prevalence of microalbuminuria and its relationship with several cardiovascular risk factors and target organ damage were evaluated in a cohort of 787 untreated patients with essential hypertension. Albuminuria was measured as the albumin-to-creatinine ratio in three nonconsecutive, first morning urine samples. The prevalence of microalbuminuria was 6.7%. Albuminuric patients were more likely to be men and to be characterized by higher blood pressure, body mass index, and uric acid levels and lower HDL cholesterol and HDL cholesterol-to-LDL cholesterol ratio. Piecewise linear regression analysis demonstrated that uric acid and diastolic blood pressure significantly influence albuminuria and together account for a large part of its variations. K-means cluster analysis performed on the entire cohort of patients confirmed that microalbuminuria is associated with a worse cardiovascular risk profile. Furthermore, microalbuminuria was associated with the presence of target organ damage (eg, electrocardiographic [ECG] abnormalities and retinal vascular changes). Age and the presence of microalbuminuria act as independent risk factors for the development of ECG abnormalities and retinal vascular changes. Cluster analysis allowed us to identify three subgroups of patients who differed in the presence or absence of microalbuminuria, retinopathy, and ECG abnormalities. We conclude that the prevalence of microalbuminuria in essential hypertension is lower than previously reported. Increased urinary albumin excretion is associated with a worse cardiovascular risk profile and is a concomitant indicator of early target organ damage.

The deletion polymorphism of the angiotensin I-converting enzyme gene is associated with target organ damage in essential hypertension.

The activity of the renin-angiotensin-aldosterone system is thought to play a significant role in the development of target organ damage in essential hypertension. An insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene has recently been associated with increased risk for left ventricular hypertrophy and coronary heart disease in the general population. The D allele is associated with higher levels of circulating ACE and therefore may predispose to cardiovascular damage. The study presented here was performed to investigate the association between the ACE genotype, microalbuminuria, retinopathy, and left ventricular hypertrophy in 106 patients with essential hypertension. ACE gene polymorphism was determined by polymerase chain reaction technique. Microalbuminuria was evaluated as albumin-to-creatinine ratio (A/C) in three nonconsecutive first morning urine samples (negative urine culture) after a 4-wk washout period. Microalbuminuria was defined as A/C between 2.38 to 19 (men) and 2.96 to 20 (women). Hypertensive retinopathy was evaluated by direct funduscopic examination (keith-Wagener-Barker classification) and left ventricular hypertrophy by M-B mode echocardiography. The distribution of the DD, ID, and II genotypes was 27, 50, and 23%, respectively. The prevalence of microalbuminuria, retinopathy, and left ventricular hypertrophy was 19, 74, and 72% respectively. There were no differences among the three genotypes for age, known duration of disease, body mass index, blood pressure, serum glucose, uric acid, and lipid profile. DD and ID genotypes were significantly associated with the presence of microalbuminuria (odds ratio, 8.51; 95% confidence interval, 1.07 to 67.85; P = 0.019), retinopathy (odds ratio, 5.19; 95% confidence interval, 1.71 to 15.75; P = 0.005) and left ventricular hypertrophy (odds ratio, 5.22; 95% confidence interval, 1.52 to 17.94; P = 0.016). Furthermore, patients with DD and ID genotypes showed higher levels of A/C (3.6 +/- 0.9, DD; 2.6 +/- 0.7, ID; 0.9 +/- 0.2 mg/mmol, II; P = 0.0015 by analysis of variance) and increased left ventricular mass index (152 +/- 4.7, DD + ID versus 133 +/- 5.7 g/m2, II; P = 0.01) compared with II patients. The D allele was significantly more frequent in patients with microalbuminuria (odds ratio, 2.59; 95% confidence interval, 1.24 to 5.41; P = 0.013) and in those with retinopathy (odds ratio, 2.44; 95% confidence interval, 1.21 to 4.90; P = 0.015). Multiple regression analyses performed among the entire cohort of patients demonstrated that ACE genotype significantly and independently influences the presence of retinopathy, left ventricular hypertrophy, and microalbuminuria. In conclusion, the D allele of the ACE gene is associated with microalbuminuria as well as with retinopathy and left ventricular hypertrophy, and seems to be an independent risk factor for target organ damage in essential hypertension.

An experimental model of biofilm detachment in liquid fluidized bed biological reactors.

Dimensional analysis was applied for the description of biofilm detachment in liquid fluidized bed biological reactors. This technique allowed the identification of the significant parameters influencing detachment mechanisms and suggested suitable experiments for the characterization of involved phenomena. The influence of the significant variables was established on a lab-scale reactor and an empirical model was proposed to correlate experimental results. The detachment rate was strongly dependent on liquid velocity, while the influence of other parameters, such as solid hold-up and liquid shear stress, was found to be less important.

Prevalence of micro- and macroalbuminuria and their relationship with other cardiovascular risk factors in essential hypertension.

A cohort of 227 untreated essential hypertensive patients from north-western Italy was studied in order to evaluate the prevalence of micro- and macroalbuminuria and their relationship with other cardiovascular risk factors. Albuminuria was evaluated as the albumin to creatinine ratio (Alb/Cr) in three non-consecutive first morning samples. The prevalence of microalbuminuria and macroalbuminuria was 10% and 2.2%, respectively. Albuminuric patients showed higher blood pressure, serum creatinine, triglycerides and uric acid as well as a greater prevalence of retinopathy. Stepwise multiple regression analysis demonstrated that only a small part of variations in albuminuria was explained by changes in blood pressure. Duration of disease did not seem to influence microalbuminuria. The presence of hypertensive retinopathy was associated with greater albuminuria, longer duration of hypertension, and higher prevalence of major ECG changes, but not with higher blood pressure levels. Microalbuminuria, rather than a consequence of elevated blood pressure levels, seems to be a marker of a syndrome featuring, among other characteristics, essential hypertension. Furthermore, microalbuminuria must be considered as an independent cardiovascular risk factor.