Effect of biostimulation on biodegradation of dissolved organic carbon in biological filters

The addition of labile organic carbon (LOC) to enhance the biodegradation rate of dissolved organic carbon (DOC) in biological columns was studied. Acetate standard solution (NaAc) and Luria Bertrani (LB) medium were used as LOC as biostimulants in glass column system used for measurements of biodegradable dissolved organic carbon (BDOC). The addition of LOC related with the increase of total DOC in sample. The concentration of BDOC increased up to 7 and 5 times and was utilized after 24 min. contact time. The biodegradation rate constant was increased at least 26 times during adaptation-biostimulation period. There was a strong positive correlation between the biodegradation rate constant and the concentration of BDOC. Biostimulation period ranged from 24 to 53 h for NaAc biostimulant and from 20 to 168 h for LB. The study has shown that LOC could be used as stimulator to enhance the biodegradation rate of DOC during biofiltration

CLEANING OF CERAMIC ULTRAFILTRATION MEMBRANES AFTER FILTRATION OF HAY HYDROLYSATE

Hydrolysis of the lignocellulosic biomass results in the release of high-value chemicals that during industrial processing can be recovered with membrane technologies. To maintain an effective performance of the membranes used in the technological processing of biomass, their regular cleaning is essential. Although several guidelines may be found for membrane cleaning in the cases of organic fouling, the data for cleaning membranes fouled by hydrolyzed lignocellulosic biomass is limited. Current research is aimed to evaluate physical (air backpulse) and common cheap chemical membrane cleaning methods. The results showed that air backpulse alone had a minor (9%) effect on the membrane cleaning. The alternation of NaOH (1 %) solution with the NaClO (200 mg/L of Free chlorine) was the most effective approach for membrane cleaning. The cleaning effectiveness was 95.1 % for 50 nm membrane and 89 % for 200 nm membrane, indicating that membranes used for hydrolyzed lignocellulosic biomass filtration can be effectively cleaned using affordable and accessible chemicals

APPROBATION OF MICROBIALLY AVAILABLE PHOSPHORUS (MAP) DETERMINATION METHOD BY FLOW CYTOMETRY

Phosphorus (P) is among the most important nutrients required for bacterial growth. It has a great influence on microbial activity even at very small concentrations. Existing chemical methods are not able to determine P at low enough concentrations and to quantify biologically available phosphorus fractions. Therefore, a method of microbially available phosphorus (MAP) determination is used to quantify the amount of P at concentrations below 20 µg/l. Additionally, this method determines the amount of P that can be directly used by microorganisms. Originally it was determined by inoculating sample by Pseudomonas fluorescens (now Ps. brenneri) P17 strain and spread-plated on R2A agar for enumeration. Further, a more rapid method was developed by replacing heterotrophic plate count (HPC) by flow cytometry (FCM). In this paper the use of FCM for MAP determination is validated and compared with HPC method. The results of calibration are presented. The original pure P17 strain was used as inoculum and standards with different PO4-P concentrations were inoculated at 30°C. The gained yield factor by FCM was 1.59x108. FCM results showed strong correlation (R2=0.99) with HPC results, as pure culture was used. Therefore, flow cytometry is a rapid alternative to heterotrophic plate count method for microbially available phosphorus determination

The association of spatial T wave axis deviation with incident coronary events. The ARIC cohort

BACKGROUND: Although current evidence suggests that the spatial T wave axis captures important information about ventricular repolarization abnormalities, there are only a few and discordant epidemiologic studies addressing the ability of the spatial T wave axis to predict coronary heart disease (CHD) occurrence. METHODS: This prospective study analyzed data from 12,256 middle-aged African American and white men and women, from the Atherosclerosis Risk in Communities Study (ARIC). Following a standardized protocol, resting standard 12-lead, 10-second electrocardiograms were digitized and analyzed with the Marquette GE program. The median follow-up time was 12.1 years; incident coronary heart disease comprised fatal and non-fatal CHD events. RESULTS: The incidence rate of CHD was 4.26, 4.18, 4.28 and 5.62 per 1000 person-years respectively, across the spatial T wave axis quartiles. Among women for every 10 degrees increase in the spatial T wave axis deviation, there was an estimated increase in the risk of CHD of 1.16 (95% CI 1.04–1.28). After adjustment for age, height, weight, smoking, hypertension, diabetes, QRS axis and minor T wave abnormalities, this hazard rate ratio for women fell to 1.03 (0.92–1.14). The corresponding crude and adjusted hazard ratios for men were 1.05 (95% CI 0.96–1.15) and 0.95 (0.86–1.04) respectively. CONCLUSIONS: In conclusion, this prospective, population-based, bi-ethnic study of men and women free of coronary heart disease at baseline shows that spatial T wave axis deviation is not associated with incident coronary events during long-term follow up. It is doubtful that spatial T wave axis deviation would add benefit in the prediction of CHD events above and beyond the current traditional risk factors

An overview on the reactors to study drinking water biofilms

The development of biofilms in drinking water distribution systems (DWDS) can cause pipe degradation, changes in the water organoleptic properties but the main problem is related to the public health. Biofilms are the main responsible for the microbial presence in drinking water (DW) and can be reservoirs for pathogens. Therefore, the understanding of the mechanisms underlying biofilm formation and behavior is of utmost importance in order to create effective control strategies. As the study of biofilms in real DWDS is difficult, several devices have been developed. These devices allow biofilm formation under controlled conditions of physical (flow velocity, shear stress, temperature, type of pipe material, etc), chemical (type and amount of nutrients, type of disinfectant and residuals, organic and inorganic particles, ions, etc) and biological (composition of microbial community e type of microorganism and characteristics) parameters, ensuring that the operational conditions are similar as possible to the DWDS conditions in order to achieve results that can be applied to the real scenarios. The devices used in DW biofilm studies can be divided essentially in two groups, those usually applied in situ and the bench top laboratorial reactors. The selection of a device should be obviously in accordance with the aim of the study and its advantages and limitations should be evaluated to obtain reproducible results that can be transposed into the reality of the DWDS. The aim of this review is to provide an overview on the main reactors used in DW biofilm studies, describing their characteristics and applications, taking into account their main advantages and limitations.This work was supported by the Operational Programme for Competitiveness Factors COMPETE and by Portuguese Foundation for Science and Technology through Project Phyto disinfectants - PTDC/DTPSAP/1078/2012 (COMPETE: FCOMP-01-0124-FEDER-028765), the Post-Doc grant awarded to Lucia Simoes (SFRH/BPD/81982/2011). Also, this work was undertaken as part of the European Research Project SUS-CLEAN (Contract n_FP7-KBBE-2011-5, project number: 287514) and the COST Action FA1202. The authors are solely responsible for this work. It does not represent the opinion of the Community, and the Community is not responsible for any use that might be made of data appearing herein

T-vector and T-loop morphology analysis of ventricular repolarization in ischemic heart disease

Background Sudden cardiac death (SCD) is responsible for about half of all cardiovascular deaths in the western world. Heterogeneous ventricular repolarization (VR) is a common denominator in the genesis of malignant ventricular arrhythmias responsible for SCD and the presence of coronary artery disease (CAD) is an aggravating factor. A non-invasive method reliably reflecting VR heterogeneity could therefore play a significant role in the preventive strategy against SCD. This thesis focuses on VR in CAD and acute ischemia. Aims To study VR abnormalities in patients with CAD using 3-dimensional (3-D) vectorcardiography (VCG). To assess VR at rest and during acute ischemia in patients with/without major co-morbidities, including hypertension and left ventricular hypertrophy (LVH), applying recently developed VCG parameters. To assess VR alterations in relation to the amount of the ischemic myocardium. To explore the prognostic value of these parameters in terms of cardiovascular (CV) mortality and morbidity during long-term follow-up. Studies I-II As a first step, VR measures at rest and during acute ischemia were analyzed in a subgroup of 56 CAD patients selected to create a relatively homogeneous group without obvious confounders affecting the VR response, e.g. previous myocardial infarction (MI) or LVH. They were identified from a cohort of 187 patients planned for an elective single-vessel percutaneous coronary intervention (PCI). In the next step, the electrophysiological consequences of myocardial hypertrophy were assessed in all 187 CAD patients, including 33 with LVH and 54 with a history of hypertension. VR was examined in terms of the maximum T-vector orientation in space by azimuth and elevation and the angular relationship with the main depolarization vector, the QRS-T angle. The planarity of the T loop (Tavplan), its shape and roundness (Teigenv) and the area under the 3-D T-wave (Tarea) were analyzed as well. At rest, the Tarea and Teigenv differed significantly between CAD patients and healthy controls. Acute ischemia most consistently reduced T-loop planarity and increased its roundness and area under the T-wave. Only occlusion of the left anterior descending artery (LAD) significantly changed the T-vector orientation. Patients with LVH had not only the most abnormal VR at rest but also a significantly more pronounced VR response during coronary occlusion. Patients with a history of hypertension (without LVH) had mean parameter values between the LVH patients and those with neither hypertension nor LVH. Study III The relationship between the size and location of the myocardium at risk (MAR) and the VR response during ischemia was studied during elective PCI in another cohort of 35 CAD patients. Tc-99m-sestamibi was administered intravenously immediately after coronary occlusion. The perfusion defect severity and MAR were quantified by automated software. The VR measures during maximum ischemia was compared with baseline and the changes (delta) were related to the MAR and the occluded artery. There were significant correlations between MAR size and ST-segment alterations (STC-VM, deltaST-VM), as previously shown, but also with deltaTavplan and deltaTeigenv, although they were most prominent during LAD occlusion, which induced the largest MAR size. Study IV In a longitudinal cohort study, the 187 CAD patients (Study II) were followed for 8±1 years. There were 16 CV deaths, 19 new MIs and more then 70 additional revascularizations. CV death was independently predicted by a prolonged QRS duration and a widened QRS-T angle, along with left ventricular dysfunction or hypertrophy. MI was most consistently predicted by increased Tavplan. Repeat revascularization was predicted by the presence of diabetes and the absence of stent implantation. Conclusion CAD patients displayed changes in VR compared with the healthy controls, even in the absence of major co-morbidities. Short-lasting LAD occlusion induced the most pronounced VR changes, which were associated with the largest amount of jeopardized myocardium compared with the other coronary arteries. Myocardial hypertrophy was associated not only with the most abnormal VR at baseline but also with the most exaggerated VR response during ischemia. These observations are consistent with epidemiological, experimental and autopsy data showing a predominance of LAD disease and/or myocardial hypertrophy in SCD victims. A widened QRS-T angle was independently associated with the CV deaths, which is consistent with previous studies, and an increased distortion of the T-loop (Tavplan) with subsequent MI, which is a novel finding. VCG-based VR analysis might prove to be a useful tool in assisting the identification of risk individuals and for following the effects of preventive therapies

Current research about biological stability of drinking water in the Riga water supply system

Literatūras apskats par faktoriem, kas ietekmē dzeramā ūdens mikrobioloģisko stabilitāti

Aksiālās dispersijas ietekme uz dzeramā ūdens kvalitātes izmaiņām dzeramā ūdens apgādes tīklā

Tīrs dzeramais ūdens ir jebkuras civilizācijas pamatā, līdz ar to tā kvalitātei ir jāpievērš ļoti liela uzmanība. Lai arī dzeramā ūdens kvalitāte ūdens sagatavošanas un attīrīšanas iekārtās ir augsta, tā mēdz pasliktināties dzeramā ūdens apgādes tīklā. Pasaulē problēmas, kas saistītas ar dzeramā ūdens estētiskām īpašībām, dzīvībai bīstamu dezinfekcijas blakusproduktu samazināšanu, kā arī attiecīga rīcības plāna sagatavošanai, gadījumos, ja patērētāji saindējas ar nekvalitatīvu dzeramo ūdeni, arvien biežāk parādās prasībās dzeramā ūdens apgādes sistēmu apkalpojošajiem uzņēmumiem. Šīs visas problēmas ir saistītas ar dzeramā ūdens kvalitātes izmaiņām dzeramā ūdens apgādes tīklā. Šādu problēmu risināšanai un prognozēšanai tiek izmatotas datorsimulācijas. Datorsimulācijām izmantotās modelēšanas programmas ir neprecīzas, jo tās nespēj precīzi modelēt, kā dzeramā ūdens apgādes sistēmā izplatās ķīmisko vai bioloģisko vielu daļiņas, jo visās līdz šim izstrādātajās modelēšanas programmās ir iestrādāts pieņēmums, ka daļiņas cauruļvados kustas tikai ar advekcijas mehānisma palīdzību un netiek ņemta vērā aksiālās dispersijas ietekme. Tas ir, tiek pieņemts, ka daļiņas kustas reizē ar ūdens daļiņām. Cauruļvados plūstošu šķidrumu aksiālā jeb garuma dispersija rodas masas transporta procesā, kad piesārņojuma daļiņas ūdenī nevienmērīga plūsmas šķērsgriezuma ātruma sadalījuma ietekmē izplešas garenvirzienā. Darba mērķis ir ar mērījumiem speciāli izveidotā miniatūrā ūdensapgādes tīklā, noskaidrot aksiālās dispersijas ietekmi uz piesārņojuma izplatību ūdenī un līkumu ietekmi uz to, kā arī pilnveidot ūdensapgādes tīklu modelēšanā izmantoto programmu Epanet 2.0 iekļaujot tajā aksiālās dispersijas ietekmi. Lai noteiktu potenciāla piesārņojuma izplatību, tiek veikti eksperimenti pielietojot tā saucamo „treiseru” metodi. Eksperimentos ūdens apgādes sistēmā tiek ievadīts šķidrums ar paaugstinātu elektrovadītspēju (EVS), kurā pēc tam tālāk tīklā tiek mērīta ar rokas un on-line EVS mērītājiem (Cond 315i, (WTW, Germany) ar mērījumu precizitāti 1.5% un HACH 3400scTM (Dr.Bruno Lange GmbH&Co, Germany) ar mērījumu precizitāti 2 %). Kopumā tika veikti 48 eksperimenti, lai noskaidrotu piesārņojuma izplatīšanās atkarību no līkumu skaita cauruļvadā, attāluma un plūsmas ātruma. Eksperimentu veikšanai tiek izmantota daļa no RTU ŪITK telpās esošās pilota iekārtas, kā arī tika speciāli konstruēts 36 metru garš taisns cauruļvads. Attēlā redzama atšķirība starp modelēto piesārņojuma izplatību un eksperimentāli noteikto. Darba rezultāti ļaus paredzēt citu vielu piemēram Bacillus subtilis sporu, izplatību minētajā pilota iekārtā, kā arī dos iespēju pilnīgāk izprast vielu koncentrāciju izmaiņas ūdensapgādes sistēmās

The Full-Scale Study on Phosphorus Addition to Biologically Activated Carbon Filters

Darbā apskatīta fosfora dozēšanas ietekme uz organisko vielu izdalīšanu bioloģiski aktīvās ogles filtros. Pētījums veikts ūdens attīrīšanas iekārtās, kurās mikroorganismu attīstību limitē fosfors. Organisko vielu izdalīšanu biofiltros mērījām nosakot kopējā organiskā oglekļa (TOC) koncentrāciju, ķīmiskā skābekļa patēriņu un ultraviolēto absorbciju. Mikroorganismu koncentrāciju biofiltru izplūdē noteicām mērot heterotrofo koloniju skaitu. TOC koncentrācija biofiltrā ar fosfora (50 µg P/l) dozēšanu bija 5.13 mg l-1 un filtrā bez dozēšanas 5.52 mg l-1. HPC izplūdes ūdenī no biofiltra ar fosfora dozēšanu bija par vienu kārtu lielāks nekā filtrā bez fosfora dozēšanas jeb 2573 kolonijas veidojošās vienības ml-1 and 265 kvv ml-1katrā. Pētījums parādīja, ka nebija ievērojamas statistiskas atšķirības organisko vielu izdalīšanai filtrā ar fosfora dozēšanu un filtrā bez dozēšanas