Application of ARIMAX model for forecasting paddy production in Trincomalee district in Sri Lanka

In the post-war climes, the government’s mandates focus on reviving one of the paddy production region Trincomalee district in SriLanka to meet the growing demands of the nation. Such a rehabilitation program requires the understanding of how the paddy producing industry has fared along the historical time-lines. This understanding is essential for developing the necessary development plans for the Rice sector. When an ARIMA model includes other time series as input variables, the model is referred to as an ARIMAX model. Pankratz (1991). In this paper, ARIMAX model has been applied to forecast annual paddy production with includes rainfall time series as input variable for both seasons in this district. The validity of the model is verified with various model selection criteria such as Adj R2, minimum of AIC and SBC lowest MAPE value

Submerged microfiltration coupled with physcio-chemical processes as pretreatment to sea water desalination

In this study, the critical flux of the submerged membrane system was experimentally evaluated when it was used for seawater with and without pre-treatment. In this study, different processes such as flocculation with ferric chloride (FeCl3) and different doses of PAC adsorption were used as a pre-treatment. The pretreatment of flocculant of 2 mg/L of FeCl3 and adsorption with the dose of 1 g/L PAC showed an improvement in the critical flux from 5 L/m2.h to 6.7 L/m2.h and 13.3 L/m2.h respectively. The performance of these pretreatments was also determined in terms of modified fouling index using ultrafilter membrane (UF-MFI). UF-MFI and SDI indicated that PAC adsorption was a better pretreatment than flocculation for the seawater used in this study. Molecular weight distribution (MWD) of seawater organic matter was also examined after different pretreatments. MWD of the raw seawater was mainly in the range from 1510 to 130 Da. It is observed that FeCl3 flocculation and PAC adsorption as pretreatments partially removed the organic matter of 1510 Da and 130Da respectively. © 2009 Desalination Publications

Review of stormwater quality, quantity and treatment methods part 2: Stormwater: Quality modelling

In this paper, review of stormwater quality and quantity in the urban environment is presented. The review is presented in three parts. This second part reviews the mathematical techiques used in the stromwater quality modelling and has been undertaken by examining a number of models that are in current use. The important features of models are discussed

Is semi-flocculation effective as pretreatment to ultrafiltration in wastewater treatment?

In this study, ferric chloride (FeCl3) flocculation was used as a pretreatment to ultrafiltration (UF) in treating synthetic wastewater containing synthetic organic matter (SOM). The effect of flocculant dose was studied in terms of organic removal and membrane flux decline. The UF with optimum dose of FeCl3 (68 mg L-1) did not experience any flux decline during the whole operation of 6 h. The preflocculation with a smaller dose of 20 mg L-1 of FeCl3 led to a severe flux decline in the UF (more than 65% in 6 h). To understand the phenomenon of the flux decline of UF, the MW ranges of SOM removed by different doses of FeCl 3 and by the post treatment of UF were studied. Flocculation with at least 50 mg L-1 of FeCl3 dose was found to be necessary to avoid any significant flux decline and to obtain superior DOC removal. © 2004 Elsevier Ltd. All rights reserved

Membranes coupled with physico chemical treatment in water reuse

In this study, short-term experiments were conducted with different configurations of membrane hybrid systems to treat biological treated sewage effluent containing refractory organic pollutants: (i) submerged hollow fiber microfiltration (SMF) alone; (ii) spiral flocculator (SF)-SMF without settling; (iii) SF-PAC-SMF without settling and (iv) SMF with magnetic ion exchange resin MIEX® pretreatment. The results indicated that the pre-flocculation of SF could improve the mitigation of membrane fouling significantly even when the system was operated at a high membrane filtration rate. The transmembrane pressure (TMP) of SF-PAC-SMF only increased marginally (0.8 kPa over 8 hours). SF-SMF without the addition of powdered activated carbon (PAC) also took a relatively long duration for the TMP to increase. The TMP only increased by 2.5 kPa over 8 hours. The SF-PAC-MF system resulted in a high dissolved organic carbon (DOC) removal of more than 96%. When used as pre-treatment to submerged membranes, the fluidized bed MIEX® contactor could remove a significant amount of organic matter in wastewater. This pre-treatment helped to reduce the membrane fouling and kept the TMP low during the membrane operation. © IWA Publishing 2010

Enhanced removal of nitrate in an integrated electrochemical-adsorption system

© 2017 Elsevier B.V. The electrochemical (EC) method of removing pollutants in water is a widely used process in water and wastewater treatment. An EC-adsorption integrated system was investigated to test whether the simultaneous removal of nitrate by the two processes would be better than removal utilising the individual EC and adsorption methods. In the integrated system, an adsorbent (ion exchange resin - Dowex 21k XLT) was placed inside a stainless steel box that served as an anode with a Cu plate as cathode. In an experiment using 2 L nitrate solution containing 20 mg N/L and 2 g adsorbent the rate of nitrate removal in the integrated system was initially fast with 35% removed in 30 min, though slowing down later. The rate of removal increased with increasing current, voltage and pH up to 7 but decreased as the distance between the electrodes also increased. The optimum nitrate removal of 67% was obtained at pH 7, 1 A, and 31 V for a distance of 1 cm between the electrodes after 180 min. The amount of nitrate removed fell when sulphate was present in the integrated system due to sulphate competing with nitrate for adsorption. Concentration of ammonium produced by nitrate reduction in the EC system was reduced in the presence of adsorbent. Nitrate removal in the integrated system is approximately equal to the sum of the removals in the two individual processes

Influence of bioreaction on a long-term operation of a submerged membrane adsorption hybrid system

This study investigates the long-term performance of a submerged membrane adsorption hybrid system (SMAHS) for organic matter removal from synthetic wastewater representing biologically treated wastewater by using a low dose of powdered activated carbon (PAC). A simple periodic backwash system is used to de-clog the hollow fiber membrane. In this reactor, bioreaction takes place due to the growth of the biomass in the system. This hybrid system was able to remove effectively the small- and large-molecular weight organic matters from 270 to 36,270 Da. The effect of PAC replacement in the reactor was also studied and it was shown that PAC replacement could enhance both biological activity and adsorption. With PAC replacement of 2.5%(total amount) per day, the total organic carbon (TOC) removal efficiency was 10% higher than without PAC replacement. In another long-term experiment, the TOC removal efficiency was maintained over 85% even after 55-day operation (with PAC replacement rate of 2.5%(total amount) every two days). © 2006

Impact of prospective measurement of outflow tracts in the prediction of coarctation of the aorta

Background: Prenatal diagnosis of coarctation of the aorta (COA) is associated with reduced mortality and morbidity, however, accurate prenatal prediction remains challenging. To date, studies have measured the outflow tracts retrospectively to gauge the potential to predict COA. Our primary objective was to evaluate prospectively acquired measurements of the outflow tracts in prenatally suspected COA. A secondary aim was to report the postnatal prevalence of bicuspid aortic valve in this cohort. Methods: Measurement of the aortic valve, pulmonary valve, distal transverse aortic arch (DTAA) and arterial duct (AD) diameters were undertaken routinely in fetuses with suspected COA between 2002–2017. Using published reference ranges based on >7000 fetuses from our own unit, z scores were computed. Results: COA was confirmed after birth in 77/149 (52%) cases. DTAA z score and the z score of DTAA:AD were smaller in cases with confirmed COA compared to false positive (FP) (-2.8 vs -1.9, p=0.039; -3.13 vs -2.61, p=0.005, respectively). Multiple regression analysis demonstrated that z scores of DTAA and AD were the only significant predictors (p=0.001). Bicuspid aortic valve was identified in 30% of the FP group. Conclusion: Measurement of the DTAA and AD z scores can be used to attribute risk for postnatal COA in a selected cohort. The significance of the high incidence of bicuspid aortic valve in FP cases merits further study both with respect to aetiology and longer- term significance

Simultaneous adsorption of Cd, Cr, Cu, Pb, and Zn by an iron-coated Australian zeolite in batch and fixed-bed column studies

© 2015 Elsevier B.V. Excessive levels of heavy metals in water are an environmental hazard. An Australian zeolite with (ICZ) and without (Z) iron-coating, was used to remove five heavy metals from aqueous solutions using adsorption in batch and column experiments. The batch study showed that the Langmuir adsorption capacities of heavy metals on Z and ICZ at pH 6.5 and ionic strength 10-3M NaNO3 were in the order Pb>Cu>Cd>Cr, Zn for single metal (5.0-11.2mg/g) and for mixed metals solution (3.7-7.6mg/g). The data for the kinetics of adsorption satisfactory fitted to both the pseudo-first and second order models with fits slightly better for the latter model. Data fitted to a diffusion model revealed that adsorption took place in two or more than two different stages: a fast external surface adsorption, and a gradual adsorption controlled by both film diffusion and intra-particle diffusion. The column adsorption data were fairly well described by Thomas model, with the order of Thomas adsorption capacity following a similar trend as in the batch study. In both batch and column experiments, the adsorption capacities were higher for ICZ than for Z and were generally lower in mixed metals system than in single metals system. Leaching of used ICZ columns with 0.1M HCl, resulted in 64-93% of adsorbed metals being desorbed, and 10% of Fe being dissolved from the ICZ

Reference ranges for the size of the fetal cardiac outflow tracts from 13 to 36 weeks gestation: a single-center study of over 7000 cases

BACKGROUND: Assessment of the outflow tract views is an integral part of routine fetal cardiac scanning. For some congenital heart defects, notably coarctation of the aorta, pulmonary valve stenosis, and aortic valve stenosis, the size of vessels is important both for diagnosis and prognosis. Existing reference ranges of fetal outflow tracts are derived from a small number of cases. METHODS AND RESULTS: The study population comprised 7945 fetuses at 13 to 36 weeks’ gestation with no detectable abnormalities from pregnancies resulting in normal live births. Prospective measurements were taken of (1) the aortic and pulmonary valves in diastole at the largest diameter with the valve closed, (2) the distal transverse aortic arch on the 3 vessel and trachea view beyond the trachea at the distal point at its widest systolic diameter, and (3) the arterial duct on the 3 vessel and trachea view at its widest systolic diameter. Regression analysis, with polynomial terms to assess for linear and nonlinear contributors, was used to establish the relationship between each measurement and gestational age. The measurement for each cardiac diameter was expressed as a z score (difference between observed and expected value divided by the fitted SD corrected for gestational age) and percentile. Analysis included calculation of gestation-specific SDs. Regression equations are provided for the cardiac outflow tracts and for the distal transverse aortic arch:arterial duct ratio. CONCLUSIONS: The study established reference ranges for fetal outflow tract measurements at 13 to 36 weeks’ gestation that are useful in clinical practice