Filtrate Quality Research Articles

Digital audio signal filtration based on the dual-tree wavelet transform

A new method of digital audio signal filtration based on the dual-tree wavelet transform is described. An adaptive approach is proposed that allows the automatic adjustment of parameters of the wavelet filter to be optimized. A significant improvement of the quality of signal filtration is demonstrated in comparison to the traditionally used filters based on the discrete wavelet transform.

Evaluation on the dewatering process of cyanobacteria-containing AlCl3 and PACl drinking water sludge

Most researches focused on the high efficiency removal of cyanobacteria from water phase during drinking water treatment, but did not address the potential danger of cyanobacterial cells being transferred into the sludge, especially during the dewatering process. In this study, the characteristics of cell lysis and microcystin (MC) release in the filtration of cyanobacteria-containing sludge were investigated. By evaluating filtration rates, filtrate microcystins (MCs) and turbidity levels, and SEM micrographs of the sludge in different operating conditions, the influences of mechanical actions and physical/chemical effects on the integrity of cyanobacterial cells were explicated, and the corresponding operation conditions were also optimized. The results showed that the sludge accumulation on unit filter area had significant influence on sludge dewatering characteristics, and with increase in the volume of sludge filtrated, more and more sludge accumulated on the surface of the filter media, resulting in reduced filtration rates and potential cyanobacteria lysis. More hydrophilic filter media with lower porosity should be chosen to enhance filtration efficiency. Compared with positive pressure filtration, vacuum filtration with low-destructibility should be a better choice considering the MC release. Under increased vacuum pressure, cyanobacteria-containing sludge had increasing filtration rate without causing damage of cyanobacterial cells. While the storage time of cyanobacteria-containing sludge should be severely restricted in actual water supply factories (4d for AlCl3 sludge and 2d for PACl sludge) to avoid the adverse influences of cyanobacteria lysis on sludge dewaterability and filtrate quality. This study produced deeper knowledge on the fate of cyanobacterial cells and intracellular MCs in the sludge dewatering process, and the results provided valuable scientific references for volume reduction of cyanobacteria-containing sludge in the actual treatment operations.

Effects of metal ions with different valences on colloidal aggregation in low-concentration silica colloidal systems characterized by continuous online zeta potential analysis

In the removal of silicate and impurities in the acid treatment of high-alumina fly ash, the transition from silica sol to gel in the presence of metal cations has a major role in filtration and product quality. In this work, an online physical analysis method that can continuously measure zeta potential, pH, and viscosity is established for low-concentration colloidal systems. The change in zeta potential can be explained by Derjaguin.Landau.Verwey.Overbeek (DLVO) theory and model of electric double layer, which is verified by the morphology of colloids in different periods. The influences of metal cations with different valences and contents on the transition from silica sol to gel are investigated in detail. Results show that trivalent ions have a positive role in the delayed coagulation because of their hydrolysis and complexation in relatively low concentrations. By contrast, divalent and monovalent ions have a negative role in the transition from sol to gel because of the bridging effect. In terms of concentration, divalent ions have greater influence on the transition from sol to gel than monovalent ions. This established method is adaptable for the analysis of a low-concentration colloidal system and could be applied in the acid treatment of silicon-containing solid wastes. (C) 2015 Elsevier B.V. All rights reserved.

Malaysia's largest river bank filtration and ultrafiltration systems for municipal drinking water production

This paper presents a case study of Wakaf Bunut water treatment plant (the ‘plant’) in Kelantan, Malaysia. The plant was successfully commissioned in February 2013 and started operating in March 2013. It is capable of supplying up to 14 million liters a day of potable water to Tok Bali. Feasibility studies were carried out on the combination of river bank filtration (RBF) and ultrafiltration (UF) to reduce operating costs while maintaining filtrate quality. The plant is the largest municipal drinking water treatment plant in Malaysia using combined RBF and UF technologies. Actual operating data from the plant were collected and are discussed in this paper.

The Use of Free Chlorine and PolyDADMAC Coagulants to Improve Filtrate Quality and Reduce Dose in Thermally Hydrolyzed Anaerobically Digested Biosolids

The Use of Free Chlorine and PolyDADMAC Coagulants to Improve Filtrate Quality and Reduce Dose in Thermally Hydrolyzed Anaerobically Digested Biosolids

Impact of suspended solids concentration on sludge filterability in full-scale membrane bioreactors

The relation between activated sludge filterability and mixed liquor suspended solids (MLSS) concentration in membrane bioreactors (MBRs) is framed in a single hypothesis, explaining results seemingly contradictory. A total of 44 activated sludge samples were collected and analyzed on a variety of parameters, i.e. filterability, MLSS concentration, soluble microbial products (SMP) concentrations and particle size distribution in the range of 2–100μm and of 0.4–5.0μm. The sludge filterability was assessed by using the Delft Filtration Characterization method (DFCm). In order to investigate the impact of MLSS concentration, identical samples were diluted with permeate. Results showed that dilution of the samples led to an increased activated sludge filterability, but only when the starting MLSS concentration was below the apparent critical value of 10.5g/L. As opposed, the filterability of sludge with MLSS concentrations above 10.5g/L, and which was characterized by a moderate to good filtration quality, i.e. ΔR20<1 [×1012m−1], worsened when diluted. The specific resistance times the particle concentration of a cake layer obtained when filtrating sludge of moderate to good filterability and MLSS concentration above the apparent critical value was 5.5 times smaller compared to the cake layer of sludge with MLSS concentration below the critical value. Results from SMP assessment and particle counting in the range 2–100µm showed that reduction in sludge mass and de-flocculation occurred, upon dilution of all samples. However, when diluting sludge samples with MLSS concentrations exceeding 10.5g/L and which were characterized by a moderate to good filtration characteristics, there was also release of particles below 0.4µm, opposite to dilutions of samples with MLSS concentrations below 10.5g/L. We postulate that sludge, which is characterized by a moderate to good filterability, having an MLSS concentration above the apparent critical value of 10.5g/L, is likely to retain particles smaller than 0.4μm in its mass, as opposed to sludge with MLSS concentration below the apparent critical value. Our work indicates that there are optimal MLSS concentration ranges in MBR technology, to promote good filterable sludge quality in order to avoid fouling.

PERIODIC SIGNAL FILTRATION USING DIGITAL FILTERING SYSTEM CALCULATION OPTIMIZED BY APPROXIMATION

The article assesses the filtration of periodic signals of different shapes with the use of optimized calculation of discrete low pass filtering system (LPFS) orders. The calculation is based on the minimization of the difference between approximated values and filtered values of a noisy signal. To assess the feasibility of the calculation of the optimized discrete filtering system order, a series of experiments has been carried out on generation and filtration of noisy periodic signals with different signal shapes and various signal-to-noise ratios. For all of the noisy signals, optimal (relative to the original noise-free signals) and optimized (relative to the approximated signals) LPFS orders based on a minimal mean squared error (MSE) have been calculated. After calculation of MSE between filtered and original signals, it was observed that the optimal and optimized filters allow us to get comparable noisy signal filtration quality. The article is completed by the conclusions about the possibility of using the discrete filtering system order calculation optimized by approximation.

Dead-End Dynamic Ultrafiltration of Juice Expressed from Electroporated Sugar Beets

Membrane dead-end ultrafiltration of sugar beet juice (obtained from pulsed electric field assisted nonthermal pressing) was studied as an alternative method to the conventional liming-carbonation purification. A dead-end filtration module, Amicon 8200, was first used to investigate the purification efficiency of ultrafiltration with various polyethersulfone membranes (10 kDa, 50 kDa, and 150 kDa). The purity of sugar beet juice was increased from 93.6 ± 0.5 to 96.4 ± 0.8 % with a 10-kDa membrane. In order to improve the filtration flux, which declined tremendously during dead-end filtration due to membrane fouling, a rotating disk module (RDM) was then applied, and the investigation of the dynamic filtration behavior and filtrate quality of sugar beet juice was carried out. Compared with Amicon stirred module, the RDM had a much higher permeate flux and filtrate purity. The effect of rotating speed and molecular weight cutoff (MWCO) of membranes were studied. The permeate flux increased with rotating speed and pore size of membrane. The permeate flux increased significantly when the rotating speed was raised from 500 to 1,000 rpm, while it slightly increased at higher rotating speed (2,000 rpm). The purification efficiency of dynamic RDM filtration was about twice than that of filtration performed with Amicon stirring module.

Optimization of Polymer Dose Based on Residual Polymer Concentration in Dewatering Supernatant

Optimization of sludge conditioning and dewatering is a continuing challenge for wastewater treatment plants. This study investigated the use of an in-line UV–vis spectrophotometer to optimize the polymer dose during sludge dewatering. The study established a relationship between the optimum polymer dose and residual polymer concentration in filtrate using UV–vis absorbance measurements at 191.5 nm. Experiments were carried out with four different polymers (FloPolymer CA 475, CAB 4500, FloPolymer CB 4350, and FloPolymer CA 4600), and similar results were obtained from all polymers. Detection limits of the polymers ranged from 0.35 to 0.95 mg/L in centrate. The optimum polymer dose was determined based on capillary suction time (CST) and filtration tests, and a relationship between the filtrate absorbance at 191.5 nm and optimum polymer dose was established. In the under-dose range, increasing the polymer dose resulted in a decrease in filtrate absorbance due to improvement in filtrate quality. The optimum polymer dose corresponded to the minimum filtrate absorbance at 191.5 nm. When the optimum dose was exceeded, absorbance values started to increase corresponding to the increase in the residual polymer concentration in filtrate in the over-dose range. These results indicate that real-time optimization of polymer dose can potentially be achieved at wastewater treatment plants using an in-line UV–vis spectrophotometer based on the absorbance of centrate or filtrate samples at 191.5 nm.

One-year operational experience with ultrafiltration as pretreatment of seawater reverse osmosis desalination system (Maspalomas-I Plant)

The selection of a proper pretreatment for reverse osmosis (RO) systems is essential to produce a high-quality feed water in order to ensure a more sustainable and reliable operation. Traditionally, seawater RO installations have been operated with conventional pretreatments based on single- or two-staged media filtration, and occasionally preceded by coagulation/flocculation processes. In recent years, however, hollow fiber ultrafiltration (UF) technology has increasingly gained acceptance as a viable pretreatment alternative for seawater desalination, due to advantages such as greater capability to cope with fluctuations and high solid loads in raw waters (typical of open intakes), smaller footprint, higher and more consistent filtrate water quality, and higher environmental sustainability, ultimately demonstrating lower total water cost in the long-term operation. In this article, design and operational aspects of the country’s largest integrated UF and RO system to treat seawater in a remote island of Spain will be provided. Special emphasis will be given on the benefits that the UF technology has brought to the operator compared to the conventional pretreatment it replaced.

Fabrication of an anti-viral air filter with SiO2–Ag nanoparticles and performance evaluation in a continuous airflow condition

In this study, SiO2 nanoparticles surface coated with Ag nanoparticles (SA particles) were fabricated to coat a medium air filter. The pressure drop, filtration efficiency, and anti-viral ability of the filter were evaluated against aerosolized bacteriophage MS2 in a continuous air flow condition. A mathematical approach was developed to measure the anti-viral ability of the filter with various virus deposition times. Moreover, two quality factors based on the anti-viral ability of the filter, and a traditional quality factor based on filtration efficiency, were calculated. The filtration efficiency and pressure drop increased with decreasing media velocity and with increasing SA particle coating level. The anti-viral efficiency also increased with increasing SA particle coating level, and decreased by with increasing virus deposition time. Consequently, SA particle coating on a filter does not have significant effects on filtration quality, and there is an optimal coating level to produce the highest anti-viral quality.

New pretreatment media filtration for SWRO membranes of desalination plants

It is well known that seawater is contaminated with suspended solids, colloidal particles, and organic matters. Therefore, unless the contaminants are removed from the feed water prior reverse osmosis (RO) membrane, they will cause a severe membrane fouling problem by deposition on its surface. It is also known that the Foraminifera genus, Amphistegina, are found on the coasts of the Red and the Mediterranean Seas in very large quantities. Therefore, our attention in this paper is to evaluate the applicability of Amphistegina tests as new pretreatment media filtration compared with conventional sand filtration technique used for seawater desalination plants. In this work, Amphistegina tests were separated directly by sieving from fresh beach sediments with mesh size 1.0–1.5 mm. According to the operating conditions for each media filtration system, the performance of the two different systems has been evaluated. From studying the filtrate quality parameters, both media filtration systems demonstrated a similar performance in removing particulates from the feed seawater and produced permeates of acceptable quality for feeding RO systems at different temperatures of 20, 30, and 40°C and different flow rates of 20, 40, and 60 l/min. The optimum conditions were obtained using 20 l/min and 40°C, and the amphistegina filter produced water with much better quality compared with that produced by sand filter. This study is based on a semi-pilot desalination unit located in the Egyptian Petroleum Research Institute (EPRI).

Filtration characterization method as tool to assess membrane bioreactor sludge filterability-the delft experience.

Prevention and removal of fouling is often the most energy intensive process in Membrane Bioreactors (MBRs), responsible for 40% to 50% of the total specific energy consumed in submerged MBRs. In the past decade, methods were developed to quantify and qualify fouling, aiming to support optimization in MBR operation. Therefore, there is a need for an evaluation of the lessons learned and how to proceed. In this article, five different methods for measuring MBR activated sludge filterability and critical flux are described, commented and evaluated. Both parameters characterize the fouling potential in full-scale MBRs. The article focuses on the Delft Filtration Characterization method (DFCm) as a convenient tool to characterize sludge properties, namely on data processing, accuracy, reproducibility, reliability, and applicability, defining the boundaries of the DFCm. Significant progress was made concerning fouling measurements in particular by using straight forward approaches focusing on the applicability of the obtained results. Nevertheless, a fouling measurement method is still to be defined which is capable of being unequivocal, concerning the fouling parameters definitions; practical and simple, in terms of set-up and operation; broad and useful, in terms of obtained results. A step forward would be the standardization of the aforementioned method to assess the sludge filtration quality.

Study of water quality improvements at a riverbank filtration site along the upper course of the River Ganga, India

Along the upper course of the River Ganga, at Haridwar (India), production wells (PWs) (each of 10 m diameter), located at a distance of 4–250 m from the bank of either river or canal, are being used to abstract mixture of groundwater and river/canal water after passage through the soil. Water samples from river/canal and 16 PWs were analyzed in monsoon and non-monsoon periods from 2005 to 2006. A comparison of water quality clearly differentiates PW water from the surface water. TDS, conductivity, alkalinity, and hardness were found to be more in water from the PWs. During monsoon, surface water exhibited increased turbidity by 100–150 times, bacterial count by around 10 times, and conductivity by around 1.2 times compared to non-monsoon samples. The bacteriological quality of the bank filtrate was not found to vary significantly. The conductivity, however, was reduced by 20% in non-monsoon period. In monsoon months, riverbank filtration resulted in reduction of turbidity and total coliform by 2.9 and 2.6 logs, respectively. Removal of turbidity and coliform in non-monsoon was more than 0.4 and 4.2 logs, respectively. UV absorbance measured in non-monsoon period was found to be reduced by 0.4 log.

Influence of operating parameters on the performance of a household slow sand filter

The biosand filter (BSF), an intermittently operated household slow sand filter, is one of the commonly used household water purification methods in the rural areas of developing countries. In this study, long-duration tests were conducted in the laboratory to investigate the influence of two important operating parameters, namely the pause period (idle time) and the charge volume on the performance of BSF by using full-scale BSFs. The filters were charged daily with 20 or 40 L of tap water spiked with Escherichia coli or sewage with different pause periods. Results indicated that during the ripening (maturation) of the filter, which took about one month, E. coli removal was low, with an average value &amp;lt;90.0%. Maximum E. coli reduction observed in the test was around 3 log10 units. Doubling the daily charge volume from 20 L to 40 L significantly reduced E. coli removal by at least one log10 unit. Reducing residence time within the filter also impaired the filtrate quality. Cleaning of the filter considerably reduced the bacterial removal efficiency. The aesthetic quality of treated water was good, with a mean effluent turbidity of &amp;lt;1.5 NTU, and was not affected by the variations in charge volume and pause period.

Methodology for Evaluating and Monitoring of Waterworks Performance Efficiency—Part 2: Test of Filterability

The effectiveness of deep-bed filtration with respect to suspension formed during the preceding processes is evaluated by the test of filterability. The properties and concentration of the suspension being filtered are affected by the efficiency of the preceding aggregation and separation processes. The basic principles of the test of filterability are based on the mechanistic model of filtration. The equations in the mathematical model of the mechanistic conception of filtration are derived from the theory of filtration. The arrangement of the pilot filtration plant for the determination of filterability of flocculent suspension is presented in this paper. The test of filterability is carried out with a thin-layer filter element. The design of a filter element arrangement and its installation are also disclosed in this paper. The inter-dependence of the coefficient of filtration efficiency on the specific volume of intercepted suspensions, filter media grain sizes and different filtration velocities are graphically presented. In addition, the effect of the filter bed clogging resulting from the properties of different suspensions on the head loss generated, the length of filtration cycle and quality of filtrate produced are also shown in this paper.

Dynamic filtration––influence of different precipitation agents on the filtration performance using an inside-out filtration module

Recently, a new type of wastewater treatment system became the focus of scientific research: the dynamic membrane bioreactor. It is a modification of the membrane bioreactor (MBR), with the main difference that a mesh filter is used instead of the membrane for sludge separation. The effluent is not of the same excellent quality as with MBRs due to the much larger size of the mesh openings. Nevertheless, the new system has all the other advantages of MBRs, including substitution of the settling tank as well as elevated sludge concentration resulting in decreased basin volumes. However, so far little experience on performance under practical conditions is available. In this study, for the first time, results concerning the impact of different precipitation agents on filtration performance are reported. Correlation between precipitation agents, the mesh size and the operational conditions was investigated. For this purpose, dead end and cross-flow filtration tests were carried out using real wastewater samples. According to the experience, flocculation strongly interferes with the dynamic filtration process. In contrast to initial expectations, lower filtrate quality compared with the untreated reference was observed. Despite on the observed impact of flocculation on the filtration performance, dependent on the type of flocculating agent, the dynamic filtration system can be efficiently used for phosphorus removal applications.

다목적 여과저류지에서 여과수의 산출율과 수질개선도에 관한 실험연구

Abstract : A pilot-scale test-bed was operated employing three soils with different grain sizes dredged from the Nakdong River to obtain the design and operation parameters of the multi-purpose filtration pond, such as the filtrate productivity of the filter sand, the appropriate removal period of the surface clogging and the contaminant removal efficiency. The cross-flow velocities were applied stepwise ranging from 0 to 40 cm/sec in order to simulate the various velocities in the artificial stream of the pond. Results showed that a filtrate production rate of 5~3 m 3 /m 2 -day was maintained by removing the surface clogging every 7 to 13 days and that the filtrate quality was not affected by the factors of the filtrate production rate, the grain size of the filter sand and the cross-flow velocity. Results also showed that most of the removal occurred within 50 cm of the top soil and that the removal efficiencies with the filtration distance of 2.4 m were 80~95% for turbidity, 20~30% for COD, 75~90% for BOD, 5~20% for total nitrogen and 20~60% for total phosphorus, which suggested that particulate matters had a high removal efficiency.

Effect of bilateral filtration on fractal estimation of optical images of loaded material surfaces

The influence of adaptive bilateral filtration on the calculation of the fractal dimension of optical images is estimated. Filtration parameters are chosen on the basis of various criteria. The use of the maximum dispersion of the probability as the most effective parameter of estimating the image filtration quality is considered.

Separation of polyphenols and proteins from flaxseed hull extracts by coagulation and ultrafiltration

This work is devoted to the separation of polyphenols and proteins, extracted from flaxseed hulls. The separation comprised two steps: (i) coagulation of proteins by adjustment of pH and subsequent centrifugation, and (ii) ultrafiltration of supernatants. The value of pH, used for extract coagulation, varied from 13.2 to 3.0. Ultrafiltration experiments were carried out in the concentration mode (up to the final volume reduction factor of 7.5) using a batch dead-end stirred filtration cell and hydrophilic polyethersulfone membranes with nominal molecular weight cut-off 30kDa. The impact of pH on the efficiency of protein coagulation and filtration steps of polyphenol purification was investigated and optimal conditions of purification were determined. The purity of polyphenols in filtrate increased from 33.6% to 56.0% after coagulation and centrifugation at pH=4.4, and it was additionally increased to 76.6% after the ultrafiltration. The impact of pH on filtration rate decline and rejection of polyphenols and proteins was demonstrated. Filtration rate decreased and filtrate purity increased as pH decreased from 13.2 to 4.4. The decrease of filtration rate at lower values of pH was explained by formation of a less permeable filter cake of residual proteins. It was demonstrated that filter cake formation significantly increased the selectivity and resulted in a better filtrate quality.