Filter Head Loss Research Articles

A Performance Comparison of Pilot-Scale Sand Filtration and Membrane Filtration of Glafkos River Water

Surface-water treatment plants use the flocculation–precipitation method followed by gravity filters to remove suspended solids. In the present work, the replacement of gravity filters with ultrafiltration membrane units is suggested to improve the efficiency of water treatment and to reduce fixed and operational costs. A parametric pilot-scale study was conducted to compare the filtration efficiency of a deep bed and a membrane module for water-simulating river water of various turbidity degrees. Suspensions of kaolinite were prepared to simulate turbidity of the Glafkos River, Achaia Region of Greece and were filtered using a laboratory sand-bed column and a pilot ultrafiltration (UF) membrane unit. Operational parameters such as the particle concentration ratio, the flow rate, and the filter head loss were studied in the case of the granular bed. In the case of membrane filtration, the permeate flux, turbidity, and membrane permeability loss due to fouling were tested. A discussion in terms of the operational cost and environmental impacts was performed. Filtration capacity of the sand filter is a decreasing function of the flow rate and it was found less efficient than membrane ultrafiltration for increased turbidity or increased particle concentration values. Membrane ultrafiltration could achieve long-term economic profit while it is characterized by minimum environmental impact since the use of chemical reagents and the production of waste sludge are limited.

Hydraulic Performance of Self-priming Mesh Filter for Micro-irrigation in Northwest China

Using Manas riverbed sediment in Northwest China as filter media, a comprehensive study was conducted on the hydraulic performance of the mesh filter, including filtration performance and sewage performance, head loss and sewage time. Relationship among filter head loss, sewage time, flow rate, sand content, filter aperture and particle gradation was established. The results showed that at the filter aperture of 0.100 mm and the influent flow rates of 160 m3/h, 180 m3/h, 200 m3/h and 220 m3/h, the corresponding maximum head loss was 8.97 m, 11 m, 12.95 m and 15.81 m, respectively. With the increase in the influent flow rate, the head loss increased. Influent flow rate, sewage flow rate, sand content, filter aperture and particle gradation jointly affected the sewage time. The sewage time was determined to be in the range of 20–45 s. Mathematical expressions for head loss and sewage time were established through theoretical analysis and verified by the test results. The results showed that the error for the head loss and sewage time between the predicted and experimental results was less than 10%, and the regression coefficient was higher than 0.95. It has been demonstrated that the proposed equations of head loss and sewage time can be used to evaluate self-priming screen filters under various working conditions. From the results, when the sewage time was 45 s, the mesh filter can achieve a higher sewage effect and ensure the efficient operation of the next filtration cycle.

Influence of Gravel as Protection Layer on the Filter Run Time

Abstract: Since the beginning of the usage of slow sand filter (SSF) as one of the water treat-ment technologies, studies on how to enhance the performance have been conducted to date. One of the limitations in the current knowledge is regarding the method to increase the filter run time. The addition of protection layer may extend the filter run time. This paper focuses on the influence of gravel as the protection layer to the filter run time and turbidity removal. Gravel was chosen as the material of protection layer because of its low-cost and availability. A system-atic investigation by comparing only one different factor within the filter, which was protection layer, was conducted under the laboratory scale. The experimentconsisted of two filter columns namely K1 and K2. Both filters were constructed using the same filter depth, type of sand, and grain size distribution. The protection layer was added to filter K1, but not to filter K2. The sol-ids penetration and the increase of filter head loss wasused to evaluate the filter run time. A sta-tistical analysis was also carried out to examine the difference on the turbidity removal from both filters. The findings showed that by adding the protection layer, the filter run time could be extended up to 70%. Regarding to the turbidityremoval, there was insignificant difference between two filters.

Full‐Scale Prechlorine Removal: Impact on Filter Performance and Water Quality

Conversion from direct filtration to biofiltration in a full‐scale drinking water treatment plant in Halifax, N.S., was assessed in terms of filter performance (e.g., turbidity, head loss) and water quality during a 48‐month project. Conversion was achieved by removing prechlorination, with the overall objective of reducing disinfection by‐product formation. As a result of prechlorine removal, it was hypothesized that the anthracite‐sand filters would provide both particle removal and biological treatment in a single process step. When prechlorine was removed, adenosine triphosphate concentrations on the filter media increased from ∼50 to ∼200–500 ng/cm3. Filter performance analysis revealed that conversion increased the filter effluent turbidity and reduced the filter head loss accumulation rate. Unit filter run volumes and filter run times were maintained. Water quality monitoring indicated that finished water total disinfection by‐products were reduced by ∼10–20 μg/L for trihalomethanes and ∼6–10 μg/L for haloacetic acids.

Integrating organic micropollutant removal into tertiary filtration: Combining PAC adsorption with advanced phosphorus removal

Direct addition of powdered activated carbon (PAC) to a deep-bed filter was investigated at pilot-scale as a single advanced treatment stage for simultaneous removal of organic micropollutants (OMPs) and phosphorus from secondary effluent. PAC doses of 10–50 mg/L were assessed with regard to their impacts on filter performance and removal of 15 selected OMPs over a period of 18 months. The PAC was effectively retained by the filter and had no negative effect on filter head loss. Filter runtime until particle breakthrough depended mainly on coagulant dose and did not decrease significantly due to the additional PAC load. Removal of suspended solids and phosphorus by coagulation was effective independent of the PAC dose. A PAC dose of 35 mg/L PAC was suitable to remove well-adsorbing OMPs (e.g. carbamazepine, diclofenac) by >80% and medium adsorbing OMPs (e.g. primidone, sulfamethoxazole) by 50–80%. Median removals were 50–80% for well-adsorbing and 30–50% for medium adsorbing OMPs with 20 mg/L PAC. Abatement of all OMPs was low (<50%) with 10 mg/L PAC, possibly because of the high effluent organic matter content (median dissolved organic carbon (DOC) concentrations of 11.2 mg/L). In addition to adsorptive removal, relevant concentration decreases of certain OMPs (e.g. 4-formylaminoantipyrine) were attributed to biological transformation in the filter. Adsorption onto accumulating PAC in the top layer of the filter bed led to improved OMP adsorption with increasing filter runtime. The comparison of OMP removal in the pilot filter with laboratory adsorption tests demonstrates that batch test results can be applied to estimate adsorptive OMP removal in real applications.

A NEW MODEL FOR HEAD LOSS ASSESSMENT OF SCREEN FILTERS DEVELOPED WITH DIMENSIONAL ANALYSIS IN DRIP IRRIGATION SYSTEMS

ABSTRACTThis study is based on data of the hydraulic analysis of 15 types of screen filters, incorporating such technical parameters as the pipe inlet/outlet inner diameter Dp, angle between filter body and inlet/outlet a, filter pore diameter ds, filter mesh number M, water velocity of inlet/outlet vi, and average water velocity of filter pore vm to develop a dimensional head loss model. The regression coefficient is 0.951 and the correlation coefficient R between the measured value and predicted value is 0.97. Using the model to study filter head loss variations as different structure parameters change, and the variation of structure parameters would lead to the changes of vi, vm, Re and Fr, consequently resulting in head loss variation. It was found that the head loss decreases significantly as the inlet/outlet diameter and filter mesh diameter decrease. An increasing angle or filter mesh size (while keeping the filter diameter constant) does not have a significant impact on the screen filter head loss. For the screen filter structural design, the proper inner diameter of inlet/outlet and filter mesh diameter should be selected to reduce both water head loss along the path and local head loss. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Statistical significance testing of parallel pilot-scale coagulation optimization study to compare aluminum sulfate and polyaluminum chloride performance

A 14 month pilot-scale coagulation optimization study was conducted at the Peterborough Water Treatment Plant (Ontario, Canada) to compare treatment performance resulting from the application of aluminum sulfate vs. polyaluminum chloride (PACl). This paper describes results obtained from applying a statistical analysis approach to evaluate impacts on pH, turbidity, total organic carbon (TOC), ultraviolet absorbance (UVA), particle counts, chlorine residuals, filter head loss, flow rate, trihalomethanes (THMs), and nine haloacetic acids (HAA 9 ). To allow a direct comparison, parallel pilot trains were operated such that they achieved equal settled water TOC by adjusting PACl dose, (52–74% of the alum dose by weight). Settled water turbidity was significantly higher (on average 0.23 NTU) in the alum treated water when compared to PACl. For equivalent filter run-times, head loss was greater by 0.002–0.011 m h −1 when applying alum. An increase in pH by approximately 0.7 units when using PACl was observed to cause a significant increase in THM formation (10–30%).

Artificial neural networks vs. Gene Expression Programming for estimating outlet dissolved oxygen in micro-irrigation sand filters fed with effluents

Sand media filters are specially used to avoid emitter clogging when water with large amount of organic pollutants like effluents are used in micro-irrigation systems. Estimation of water quality parameters such as dissolved oxygen at sand filter outlet (DOo) is of great interest for irrigation engineers. Artificial neural networks (ANN), Gene Expression Programming (GEP) and Multi Linear Regression (MLR) based models were trained for estimating DOo using data from 769 experimental filtration cycles. Instead of considering a single configuration of the training and test data sets, which is the usual procedure for those applications in agricultural studies, the performance of those models was assessed through k-fold testing, ensuring a complete performance evaluation. In general, the GEP model tended to provide the most accurate estimations, followed by ANN and, lastly, by MLR models. After the evaluation of the models, the GEP approach was used to provide a new equation to estimate DOo based on the complete data set. This procedure revealed that only inlet DO, pH, electrical conductivity and filter head loss were necessary to feed the models. Furthermore, the consideration of leave one out or, at least, k-fold assessment should be advisable to perform a suitable evaluation of the model performance. Otherwise, conclusions drawn might be only partially valid.

Tertiary Physico-chemical Treatment of Secondary Effluent from the Chania Municipal Wastewater Treatment Plant

The present study investigated tertiary physico-chemical treatment of the secondary effluent from the Chania municipal Wastewater Treatment Plant (WTP). Laboratory experiments were carried out with the aim of studying coagulation efficiency regarding reduction of turbidity, soluble COD and phosphorus both in a conventional Coagulation-Settling treatment scheme, as well as by means of Contact Filtration. The results showed that high doses of coagulants (0,5 mmol Me+3 l-1 or higher) are required to achieve significant removals of turbidity after settling. At these high doses, soluble COD can be removed by about 50%, while soluble Phosphorus by 80-95%. Ferric Chloride demonstrated slightly better removal ability as compared to Alum. The Chania WTP effluent was also treated by Contact Filtration, using a very low dose of coagulants, 0,1 mmol Me+3 l-1. Turbidity was removed by around 50%, while at this low coagulant dose removals of COD and Phosphorus were insignificant. Filtration was effective in the first 35cm of the filter bed. No significant differences were observed between the coagulants Alum and FeCl3 in the elimination of turbidity. Nevertheless, with the use of Alum a smaller filter headloss was observed, during the first two hours of continuous filtration, in comparison with the use of FeCl3 (nearly double). No difference was observed between the headloss developed at a filter depth of 5cm as compared to that developed at a depth of 70cm. This indicates that the headloss increase was due to the accumulation of suspended and colloidal solids within the first layers of the sand filter.

Optimization of conventional water treatment plant using dynamic programming

In this research, the mathematical models, indicating the capability of various units, such as rapid mixing, coagulation and flocculation, sedimentation, and the rapid sand filtration are used. Moreover, cost functions were used for the formulation of conventional water and wastewater treatment plant by applying Clark's formula (Clark, 1982). Also, by applying dynamic programming algorithm, it is easy to design a conventional treatment system with minimal cost. The application of the model for a case reduced the annual cost. This reduction was approximately in the range of 4.5-9.5% considering variable limitations. Sensitivity analysis and prediction of system's feedbacks were performed for different alterations in proportion from parameters optimized amounts. The results indicated (1) that the objective function is more sensitive to design flow rate (Q), (2) the variations in the alum dosage (A), and (3) the sand filter head loss (H). Increasing the inflow by 20%, the total annual cost would increase to about 12.6%, while 20% reduction in inflow leads to 15.2% decrease in the total annual cost. Similarly, 20% increase in alum dosage causes 7.1% increase in the total annual cost, while 20% decrease results in 7.9% decrease in the total annual cost. Furthermore, the pressure decrease causes 2.95 and 3.39% increase and decrease in total annual cost of treatment plants.

The effect of media bed characteristics and internal auxiliary elements on sand filter head loss

Sand filters are beds of granular material placed in cylindrical metal containers. They are used as one approach for irrigation water filtration, mainly to remove organic and algae contaminants. The field effectiveness of these devices depends on their proper operation. The objectives of this study were to evaluate three commercial sand filter models, to study the effects of the internal auxiliary elements (the diffuser plate and the underdrains) and its interaction to sand particle size and media bed depth on the head loss as a function of the water flow velocity at clean water conditions. The experiment was divided in two parts. First, to assess the effects of the internal elements, the tanks (empty sand filter containers) head losses were characterized for water flow directions coincident with the processes of filtering and backwash. Second, the interactions of the internal elements with three sand particle sizes and three media bed depths were evaluated in light of the filtering flow direction. The results for the tanks showed that the different internal auxiliary elements significantly affected head loss, with the backwash flow direction generating values higher than the filtering flow direction for all evaluated equipment types. Additionally, it was observed that the head loss values were significantly affected by the sand particle size, the bed depth, the filtration velocity, and the interactions among these variables. The different models of internal elements generate distinct hydraulic performances of the sand filters, showing that they may exhibit different removal efficiencies for identical operating conditions. The research identifies the need to develop new procedures for the design of the internal elements of sand filters and for field operation conditions in order to improve localized irrigation performance.

Effects of intermittent polyelectrolyte addition on water quality in direct filtration

The effects of intermittent polyelectrolyte addition on the quality of effluent water and on the development of filter headloss were studied. Anionic and cationic polyelectrolytes were applied to two similarly constructed pilot sand filters. The surface water used in the study was obtained from Ömerli, which is one of the main drinking water reservoirs of Istanbul. Six sets of experiments were carried out. The objective of the experiments in the first three sets was to determine the type and dose of suitable polyelectrolyte. The polyelectrolytes were then added intermittently and continuously in the last three sets. Intermittent addition of polyelectrolyte produced better effluent quality and reduced the polyelectrolyte consumption by half with much less headloss. Ives' Filterability Index, which incorporates the important filtration design parameters such as effluent quality, the headloss and the velocity of filtration into a dimensionless number, was used for the comparison of the experimental results.

Small City Tackles Radium in Well Water

This article discusses a pilot study by the city of Goodview, Minnesota, for the removal of radium with hydrous manganese oxide (HMO) and coprecipitation with iron from its well water. Dual media, sand, and manganese greensand media were tested in the pilot plant, and results showed that the manganese greensand media had the lowest filter headloss buildup and would produce the longest filter runs. The media also produced the best quality water with the highest removal rate of radium and iron.

CFD Modeling of Particulate Matter Fate and Pressure Drop in a Storm-Water Radial Filter

This study examined a common form of filtration, a passive radial cartridge filter (RCF) system, to physically separate hetero-disperse particulate matter in rainfall-runoff. The RCF tested utilizes aluminum-oxide coated media with a uniform pumice substrate ( d50m =3.56 mm) gradation. To examine the RCF, this study applied laser diffraction and real-time pressure sensor measurements to validate a computational fluid dynamics (CFD) model to predict particle separation and filter head loss for hetero-disperse particulate matter (PM). Filter hydrodynamics are resolved using a macroscopic approach for the porous media with a k-e turbulence model coupled with the Ergun equation. PM fate was resolved using a discrete phase model. CFD results closely followed measured data for filtration and head-loss response for all flow rates. With influent PM at 200 mg∕L ( d50m =16.3 μm) , effluent PM ranged from 32 to 57 mg∕L for surface loading rates of 24 to 189 L∕ m2 min , respectively. There was agreement between measu...

Adaptive Neuro-Fuzzy Modeling of Head Loss in Iron Removal with Rapid Sand Filtration

Breakthrough and terminal head loss are the main parameters that determine the performance of rapid sand filters. Carman-Kozeny and Ergun equations can be applied to estimate head loss, but can only be applied to clean filter beds. Elaborated models are needed to predict head loss in dirty filters. In this study, a neuro-fuzzy modeling approach was proposed to estimate head loss in dirty filters. Hydraulic loading rate, influent iron concentration, bed porosity, and operating time were selected as input variables. Various types of membership functions were tried. Two rule-base generation methods--subtractive clustering and grid partition--were used for a first-order, Sugeno-type inference system. Using 11 rules and the grid-partition method, an optimum rule base set was developed and the lowest root mean squared error (RMSE) was obtained. Tap and deionized waters were used to obtain testing RMSE values of 1.094 and 0.926, respectively. The fit between experimental results and model outputs was excellent, with the multiple correlation coefficient (R2) greater than 0.99. Based on these findings, the authors conclude that neuro-fuzzy modeling may successfully be used to predict filter head loss.

Using chloramine as a coagulant aid in enhancing coagulation of Yellow River water in China

Considering that contaminated raw water mostly contains high Ammonia-N and a majority of water treatment plants use prechlorination process in China, efficiency of chloramines as a coagulant aid in enhancing coagulation was investigated by Jar stirring and pilot-scale tests, using Yellow River water containing high concentration of natural organic matters (NOM) and bromide in winter. The jar tests results showed that, compared with no preoxidation, preformed chloramine apparently decreased the turbidity of settled and filtered water with low dosage (2.0 mg/L), and the aid-coagulation efficiency was further enhanced with the increase of chlorine (Cl2) to Ammonia-N (N) ratio. Pilot-scale studies indicated that, in comparison to the case without preoxidation, the turbidity removal efficiency of flotation and filtration effluent water was significantly improved, the particle counts of filtered water were decreased 63.4%, the average rate of filter head loss was reduced 18.2%, and filter run time was prolonged 15.7%. Therefore, chloramine preoxidation may substantially enhance the particle separation efficiency.

Innovative physico-chemical treatment of wastewater incorporating Moringa oleifera seed coagulant

Moringa oleifera is a pan tropical, multipurpose tree whose seeds contain a high quality edible oil (up to 40% by weight) and water soluble proteins that act as effective coagulants for water and wastewater treatment. The use of this natural coagulant material has not yet realised its potential. A water extract of M. oleifera seed was applied to a wastewater treatment sequence comprising coagulation–flocculation–sedimentation–sand filtration. The study was laboratory based using an actual wastewater. Overall COD removals of 50% were achieved at both 50 and 100 mg/l M. oleifera doses. When 50 and 100 mg/l seed doses were applied in combination with 10 mg/l of alum, COD removal increased to 58 and 64%, respectively. The majority of COD removal occurred during the filtration process. In the tests incorporating alum, sludge generation and filter head loss increased by factors of 3 and 2, respectively. These encouraging treatment results indicate that this may be the first treatment application that can move to large scale adoption. The simple water extract may be obtained at minimal cost from the presscake residue remaining after oil extraction from the seed. The regulatory compliance issues of adopting ‘new materials’ for wastewater treatment are significantly less stringent than those applying to the production of potable water.

Dynamic analysis of coagulation of low turbidity water sources using Al- and Fe-based coagulants

The direct filtration system is widely used in the treatment of source waters with low and stable turbidity. We have previously indicated the importance of optimizing agitation strength GR and time TR in rapid mixing tanks in order to decrease filter head loss and treated water turbidity in direct filtration. In the present study, we employ a batch-type coagulation experimental apparatus that incorporates a high-sensitivity particle counter, where the particulate concentrations are measured continuously after injection of coagulant, in order to clarify the fundamental coagulation and microfloc formation dynamics. Specifically, it is shown that, after injection of the coagulant, coagulation and microfloc formation occur through distinct periods: an agglomeration preparation period, followed by an agglomeration progression period, and then finally an agglomeration stabilization period, and that optimization of the GR value is the most important consideration, although both the coagulant concentration and GR influence the time at which agglomeration begins in the preparatory period, the time at which agglomeration stabilizes after the progression period, and the concentration of initial particles with diameters of 1-3 microm at completion of agglomeration.

Dynamic analysis of coagulation of suspended particles in low-turbidity water sources with PACl and PSI coagulants

The direct filtration system is widely used in the treatment of source waters with low and stable turbidity. We have previously indicated the importance of optimizing agitation strength GR and time TR in rapid mixing tanks in order to decrease filter head loss and treated water turbidity in direct filtration. In the present study, we employ a batch-type coagulation experimental apparatus that incorporates a high-sensitivity particle counter, where the particulate concentrations are measured continuously after injection of coagulant, in order to clarify the fundamental coagulation and microfloc formation dynamics. Specifically, it is shown that, after injection of the coagulant, coagulation and microfloc formation occurs through distinct periods: an agglomeration preparation period, followed by an agglomeration progression period, and then finally an agglomeration stabilization period, and that optimization of the GR value is the most important consideration, although both the coagulant concentration and GR influence the time at which agglomeration begins in the preparatory period, the time at which agglomeration stabilizes after the progression period, and the concentration of initial particles with diameters of 1–3 μm at completion of agglomeration.

Improving Filtrate Quality Using Agrobased Materials as Coagulant Aid

Abstract In the present study, an evaluation of agrobased materials (ABM) as a coagulant aid in conjunction with alum has been conducted to determine their efficacy in water treatment. The agrobased materials evaluated are Surjana seed (Moringa oleifera), Nirmali seed (Strychnos potatorum) and maize (Zeemays). Experiments have been conducted simulating a conventional water treatment train consisting of coagulation-flocculation-settling and granular media filtration. Emphasis has been given to the filtration aspect of the treatment train using synthetic turbid water. The filter performance was defined by water quality and head loss development across the filter bed. When Nirmali seed or maize was used as a coagulant aid, the alum dose required was 25 and 15 mg/L, respectively, and the filtrate turbidity achieved was less than 0.2 NTU, whereas alum alone with a dose of 45 mg/L achieved filtrate turbidity levels higher than 1 NTU. Thus, the use of ABM improved the filtrate quality. Head loss in filter with Surjana seed and Maize as coagulant aids was comparable to that of alum alone, whereas it was higher when Nirmali seed was used as a coagulant aid.