Particles In Effluent Research Articles

A New Polyelectrolyte Dosing Method: Injection into Deep Bed Filter Media

The aim of this paper was to investigate a novel method of polyelectrolyte injection into deep bed filter media. The raw water and the filter media used in the pilot filters were obtained from the Omerli Reservoir that supplies one million m3/day of water to the greater city of Istanbul. A cationic polyelectrolyte was injected at the entrance of the filter and at different depths of the sand bed. The effect of polyelectrolyte injection location and method was evaluated by measuring the effluent turbidity, effluent particle count, and the head losses at different locations of the sand media. It was observed that the simultaneous injection of the polyelectrolyte on top of the filter bed and at the center can lengthen the filter run time while achieving an effluent turbidity as low as 0.06 NTU (nephelometric turbidity unit) and 4 log (99.99%) particle removal.

Modeling the Inactivation of Microorganisms Occluded in Effluent Wastewater Particles to Enhance Operation of Filtration and Disinfection Systems

In disinfection systems, incomplete penetration of chlorine into effluent wastewater particles can result in a residual population of viable microorganisms. In this work, a combined experimental and numerical approach was used to quantify inactivation of microorganisms in effluent particles and identify combinations of particle removal and chlorine dose that would result in a reduction of occluded microorganisms for six full-scale facilities in the United States with different nitrification levels. The results reveal that combined chlorine is more effective for inactivating occluded microorganisms than free chlorine; model calibration results suggest that free chlorine is less effective because it is more reactive. However, nitrified effluents appear to have lower effluent particle concentrations, and decreases in particle concentrations significantly reduce the chlorine required. Additionally, in disinfection systems that are designed and operated based on inactivation of indicator organisms, the chlorine dose may be insufficient to inactivate occluded pathogens to levels consistent with current regulations.

Crushed recycled glass as a filter medium and comparison with silica sand

AbstractThe objective of this work was to evaluate crushed recycled glass as a medium for rapid filtration. In the first part of this work, physical and hydraulic characteristics of the glass medium were studied. In the second part, pilot scale inline filtration experiments were carried out using raw waters from three different water sources. Two physically identical filter columns were operated in parallel in all the experiments. One filter contained a silica sand medium that is widely used in Turkey, whereas the other filter contained crushed recycled glass. Experiments were repeated five times as follows: (i) Without the use of a coagulant, (ii–iii) with 5 mg/L and 10 mg/L of alum, and (iv–v) with 5 mg/L and 10 mg/L of ferric chloride. Turbidity, particle counts, and head losses were measured and compared as functions of time. The following were observed: (1) Provided that a coagulant was used, the filter containing crushed glass produced effluent turbidities and particle counts similar to those obtained with the sand filter. (2) The crushed glass medium generated both a smaller clean‐bed head loss and smaller clogging head losses than those of the sand filter. It is concluded that crushed glass shows significant promise as an alternative to silica sand in rapid filtration.

Model to Quantify Removal and Inactivation of Microorganisms Occluded in Effluent Wastewater Particles Using Filtration and Disinfection Systems

A model is presented to quantify microbial occlusion in effluent particles and improve understanding of the removal and inactivation of occluded microorganisms in filtration and disinfection systems. Microbial occlusion in particles is described in the model as a function of the particle size distribution, the microbial density ( N1 ) , which is the average quantity of target microorganisms within the subset of particles that contain microorganisms, and the frequency of association ( N2 ) , which is the ratio of particles that contain at least one target microorganism. To demonstrate the model, undisinfected secondary effluent samples were collected from an extended aeration treatment facility and analyzed to determine values for the model variables, N1 and N2 for heterotrophic bacteria and aerobic endospores and N2 for total coliform bacteria. Heterotrophic bacteria were present in most effluent particles (73–100%) at high densities (7–93 per particle), whereas aerobic endospores and total coliform bacte...

Comparative analysis of macrofiltration processes used as pre-treatment for municipal wastewater reuse

Three macrofiltration processes were evaluated as a first stage of tertiary treatment of municipal wastewater. The processes studied were pressure sand filter (PSF), disc filter (DF) and mesh filter (MF). The performance of each process was assessed by analysing the effluent for suspended solids, turbidity, E. coli, nematode eggs and particle distribution analysis. In all processes, the quality of the effluent with respect to suspended solids and turbidity was found to be dependent on the influent, with the PSF achieving the best results. The effluent particle analysis likewise indicated a superior retention capacity by PSF, while the DF and MF presented an increase in small particles. All effluent contained E. coli and pathogenic nematode eggs were not detected. However, other types of nematode eggs were observed, so the presence of this pathogen in effluents cannot be discarded. Costs analysis reveal than DF and MF present a higher cost than PSF, owing to the high power consumption. These technologies may be applied as pre-treatment of tertiary disinfection process, pointing up the PSF as the most effective process, allowing direct water reuse for uses with lower quality demands.

Particle properties in granular activated carbon filter during drinking water treatment

The elemental composition and bacteria attached in particles were investigated during granular activated carbon (GAC) filtration. The experimental results showed that trapped influent particles could form new, larger particles on GAC surface. The sloughing of individuals off GAC surface caused an increase in effluent particles in the size range from 5 to 25 μm. The selectivity for element removal in GAC filters caused an increasing proportion of metallic elements in the effluent particles. The distribution of molar ratio indicated a complicated composition for large particles, involving organic and inorganic substances. The organic proportion accounted for 40% of total carbon attached to the particles. Compared with dissolved carbon, there was potential for the formation of trihalomethanes by organic carbon attached to particles, especially for those with size larger than 10 μm. The pure carbon energy spectrum was found only in the GAC effluent and the size distribution of carbon fines was mainly above 10 μm. The larger carbon fines provided more space for bacterial colonization and stronger protection for attached bacteria against disinfection. The residual attached bacteria after chorine disinfection was increased to 10 2–10 3 CFU/mL within 24 hours at 25°C.

The impact of flow surges on rapid gravity filtration

In drinking water treatment flow fluctuations or surges can occur at the filtration stage. Pilot plant tests were carried out to investigate the impact of flow surges on filter performance in this study. Moreover a filtration model was applied to analyse the impact of flow surges on filter performance and predict the experimental data obtained from pilot plant tests. Experimental results showed that flow surges caused an increase in effluent particle concentration and head loss. Theoretical analysis in this study showed that the impact of a flow surge became more significant as the filtration run approaches the particle breakthrough stage. The model was also used to fit the data from one water treatment plant. The comparison demonstrated a good agreement.

Chitosan and metal salt coagulant impacts on Cryptosporidium and microsphere removal by filtration

Maintenance of appropriate chemical pretreatment is a critical component of ensuring proper filtration performance. Pilot-scale in-line filtration studies were performed to investigate the relative impacts of chitosan, alum, and FeCl 3 coagulation on the removal of Cryptosporidium parvum oocysts and oocyst-sized polystyrene microspheres by granular media filtration. Similar removals of oocysts and microspheres were achieved when optimal coagulant doses were utilized. Sub-optimal alum and FeCl 3 coagulation resulted in a deterioration filter effluent turbidity (0.2–0.3 NTU) and total particle counts (30–100 total particles ≥2 μm/mL) that were accompanied by reduced (by ∼2–3-log) median oocyst and microsphere removals by filtration. At all doses investigated, chitosan coagulation resulted in excellent turbidity and particle reductions by filtration. Nonetheless, chitosan coagulation at doses of 0.1, 0.5, and 1.0 mg/L did not result in appreciable improvements in C. parvum oocyst removal relative to complete coagulation failure (median oocyst removals were <∼1-log). As well, oocyst-sized polystyrene microspheres appear to be reasonable indicators of C. parvum oocyst removal by in-line filtration preceded by alum and FeCl 3 coagulation, but not chitosan coagulation.

Particle size distribution dynamics during precipitative softening: Declining solution composition

Particle removal is a critical step in the treatment of surface water for potable use, and the majority of drinking water treatment plants employ precipitative coagulation processes such as alum and iron “sweep-floc” coagulation or lime softening for particle pre-treatment. Unfortunately, little is quantitatively known about how particle size distributions are shaped by simultaneous precipitation and flocculation. In an earlier paper, we demonstrated the effects of the saturation ratio, the mixing intensity and the seed concentration on the rates of homogeneous nucleation, precipitative growth and flocculation during precipitation of calcium carbonate at constant solution composition using electronic particle counting techniques. In this work, we extend those findings to systems more closely emulating the conditions in actual softening processes ( i.e., declining solution composition). Key findings include the strong dependence of the rate of flocculation on the initial saturation ratio and demonstration of the benefits of seeding precipitative softening from the perspective of optimizing the effluent particle size distribution. The mixing intensity during precipitation was also shown to strongly influence the final particle size distribution. Implications of the findings with respect to softening practice are discussed.

Characterizing Shape of Effluent Particles by Image Analysis

Particle shape of wastewater effluents were investigated by implementing a dynamic particle image analyzer which provided data on the particle count, size, shape and circularity concurrently with images. The goals of this study were to characterize removal efficiency based on size and shape parameters for an in‐line filtration process and to study correlation between size and shape parameters. Results showed that filter removal efficiency can be determined by various size and shape parameters, where different information is obtained for each analysis. This method has potential in evaluating treatment process efficiencies by coupling size and shape parameters into a meaningful tool.

Treatment of textile plant effluent by ultrafiltration and/or nanofiltration for water reuse

The textile wastewater treatment by membrane processes presents some limitations such as membrane fouling which causes a rapid flux decline. In fact, the membrane processes efficiency can be affected by membrane pore blocking or/and cake formation. In order to limit the effect of membrane fouling caused by plugging particles in textile effluent, a combination between two membrane processes was studied. The ultrafiltration (UF) was used as pretreatment for nanofiltration (NF) process. A comparison between direct NF and UF/ NF combination performances was carried out. Experimental results showed that the second treatment improved the textile permeate quality by increasing the retention values of the majority of analyzed parameters. In fact, color retention was about 95%, conductivity and total dissolved salts retentions were about 80% and the bivalent ions retention values exceeded 95%. In the case of direct NF, permeate flux remained constant until a volume reduction factor (VRF) reaching 1.35. After coupling UF with NF process, a stable permeate flux was observed until a VRF equal to 2.77. This result showed that using UF process as pretreatment for NF process improved the efficiency of textile effluent treatment by increasing the membrane run-time.

Removal of particle-associated bacteriophages by dual-media filtration at different filter cycle stages and impacts on subsequent UV disinfection

This bench-scale study investigated the passage of particle-associated bacteriophage through a dual-media (anthracite-sand) filter over a complete filter cycle and the effect on subsequent ultraviolet (UV) disinfection. Two model viruses, bacteriophages MS2 and T4, were considered. The water matrix was de-chlorinated tap water with either kaolin or Aldrich ® humic acid (AHA) added and coagulated with alum to form floc before filtration. The turbidity of the influent flocculated water was 6.4 ± 1.5 NTU . Influent and filter effluent turbidity and particle counts were measured as well as headloss across the filter media. Filter effluent samples were collected for phage enumeration during three filter cycle stages: (i) filter ripening; (ii) stable operation; and (iii) end of filter cycle. Stable filter operation was defined according to a filter effluent turbidity goal of < 0.3 NTU . Influent and filter effluent samples were subsequently exposed to UV light (254 nm) at 40 mJ / cm 2 using a low pressure UV collimated beam. The study found statistically significant differences ( α = 0.05 ) in the quantity of particle-associated phage present in the filter effluent during the three stages of filtration. There was reduced UV disinfection efficiency due to the presence of particle-associated phage in the filter effluent in trials with bacteriophage MS2 and humic acid floc. Unfiltered influent water samples also resulted in reduced UV inactivation of phage relative to particle-free control conditions for both phages. Trends in filter effluent turbidity corresponded with breakthrough of particle-associated phage in the filter effluent. The results therefore suggest that maintenance of optimum filtration conditions upstream of UV disinfection is a critical barrier to particle-associated viruses.

Filtration in a Porous Granular Medium: 2. Application of Bubble Model to 1-D Column Experiments

This paper describes the formulation of a quasi-1-D network model, referred to as the ‘bubble model’, and its application for simulating particle transport and filtration through a granular filter bed. The model comprises a series of homogeneous sites linked through bundles of cylindrical bonds that represent flow pathways through distributions of pores and pore throats. This model incorporates pore scale processes of particle sieving and infiltration are based on numerical simulations described in a companion paper. The modeling of infiltration is further refined based on detailed experimental observations and measurements of the filtration of a dilute suspension of acrylic particles through a column of glass beads reported by Yoon et al. (2005 Water Resour. Res., to appear). Their data distinguish (a) between the collection of particles on grain surfaces and at grain-to-grain contact points, and (b) between particles that are fully entrapped and those that are hindered (temporarily collected) and can later become detached. These effects are represented by two parameters that characterize the probability of attachment and are linked to the surface roughness of the grains; one that describes the minimum particle size that can be fully entrapped, and one that describes the detachment rate. These parameters can be readily calibrated from conventional measurements of effluent concentration and effluent particle size distribution. Detailed comparisons with the data reported by Yoon et al. show that the proposed bubble model is able to achieve reliable predictions of the spatial distribution of particles within the filter bed following phases of particle injection and washing.

Aspects of particle attachment in filtration

Granular media filtration is used almost universally as the last particle removal process in conventional water treatment plants, but every particle cannot be removed. Laboratory-scale filtration experiments were performed at a filtration velocity of 5 m/h using spherical glass beads with mean diameter of 0.55 mm as collectors; the 10 cm depth ensured particles would be in the effluent. Particle suspensions (Min-U-Sil 5) with 1.7 μm mean particle size were filtered at pH values of 3.0, 4.0, and 5.0, all above the isoelectric point (near pH 2.0). Zeta potential distribution (ZPD) and particle size distribution (PSD) of influent and effluent particles were measured. More favorable particles, i.e. particles with smaller surface charge, were well attached to the collectors during the early stage of filtration. This selective attachment of the lower charged particles caused the ZPD of the effluent to move to a more negative range. However, the ZPD did not keep moving to a more negative range during later stages of filtration, and this result was thought to be caused by two reasons: ripening effects and detachment of flocs. In the early stages of filtration, particles were captured better at pH 3.0 than at the higher pH values (as expected), but this trend reversed at a cumulative hydraulic loading (CHL) of only 5–10 m3/m2. Particle breakoff apparently occurs as flocs of particles that are initially captured individually, as indicated by the trends for different particle sizes. At pH 3.0, particles in the 3–5 μm range had worse removal after a CHL of 5 m3/m2, whereas removal improved through the entire CHL of 20 m3/m2 for all size particles at pH 4.0. Chemical parameters such as zeta potential can be important during the initial stage of filtration, but their importance can decrease over time depending on the specific chemical conditions. The influent particle size distribution and the removal of certain size particles during the initial stage can significantly influence ripening which, in turn, can influence the overall particle removal efficiency. Better initial particle removal does not necessarily mean better overall particle removal.

Impact of suspended particles and enhancement techniques on ultraviolet disinfection of a secondary effluent

The concentration of suspended solids in the secondary effluent often varies widely, leading to frequent adjustment of the UV dosage to meet the disinfection criterion. In addition, a desired disinfection rate is difficult to achieve sometimes. The authors studied the particle size distribution, contribution of particle-associated Fecal Coliform (F.C.), and their influences on UV disinfection. A combined disinfection process (chlorination with a subsequent UV disinfection) was tested to improve the disinfection effect. The results indicated that the content of suspended solids, especially that of large particles, has a strong impact on UV disinfection efficiency; Dτ;10µm particles associated F.C. are difficult to be disinfected and are the main part of the tailings of F.C. inactivation curves. Pre-chlorination could decrease the number of particles in the secondary effluent and transform the large particles into small ones, reducing the influence of particles on UV disinfection and enhancing the resistance ability of the combined process to particle loading.

Suspended particle effects on ultraviolet light disinfection of effluent and the improvement

The concentration of suspended solids of effluent from secondary clarifiers often varies in a wide range, therefore the dose of ultraviolet light (UV) disinfection process need to be adjusted to meet the disinfection criterion at high frequency, and the desired disinfection effect is difficult to be ensured. The particles size and particle-associated Fecal Coliform (F.C.) contribution, and their influence on UV disinfection effects were investigated, and chlorination/UV combined disinfection process (chlorination/UV disinfection process) was used. The results showed that suspended solids content has a major impact on UV disinfection efficiency, especially the large particle size fraction. D&amp;gt;10µm particles associated F.C. is difficult to be disinfected and is the main part of the tailings of F.C. inactivation curve. Pre-chlorination could reduce the number of particles in effluent, and make large particles decrease to small ones. Therefore, the influence of particles on UV disinfection could be reduced after pre-chlorination, and the resistance ability to particle loadings of combined process was enhanced. Furthermore, the combined process has the advantage of low toxicity, low operational/maintenance costs, and is easy to be established not only in wastewater plants constructed already but ones to be about to be constructed.

The effect of polymeric flocculants on floc strength and filter performance

Polymeric flocculants are widely used throughout the water industry as flocculant aids, they are known to increase floc density and aid settlement in the clarification stage of the water treatment process. In this research, polymeric flocculants were used to improve floc strength prior to filtration on a dissolved air flotation (DAF) plant in an attempt to prevent filter breakthrough. A modified jar test procedure using a PDA (photometric dispersion analyser) optical flocculation monitor was developed in order to evaluate the system floc strength. Filtration trials were carried out on a pilot filter rig situated on a surface water treatment works in Yorkshire. The filter feed originated from the main plant filter channel. Filter performance was assessed by continuous online monitoring of effluent particle counts, turbidity and headloss over the period of the filter run. Results indicated that low doses of polymeric flocculants had a beneficial effect on filtered water quality, as measured by particle counts, turbidity, UV254 absorption and dissolved organic carbon (DOC). Polymeric flocculants also had the effect of extending filter run length. The modified jar test results indicated that the flocculants used improved the floc strength and enhanced reflocculation of the micro flocs present after the flotation process.

Use of biogenic sulfide for ZnS precipitation

A 600 ml continuously stirred tank reactor was used to assess the performance of a zinc sulfide precipitation process using a biogenic sulfide solution (the effluent of a sulfate-reducing bioreactor) as sulfide source. In all experiments, a proportional-integral (PI) control algorithm was used to control the pH and the sulfide (S 2−) concentration at the desired level in the precipitator. The pS (defined as: −log [S 2−]) and pH were optimised using a chemical Na 2S solution as sulfide source. A S 2− concentration of 10 −15 M (i.e. pS 15) was found to be optimal for zinc sulfide precipitation, resulting in a residual zinc concentration of 0.07 mg/l from a 3 g/l Zn 2+ influent, for both chemical Na 2S and biogenic sulfide solutions. The mean particle size of the ZnS precipitates at pS 15 and pH 6.3 was 7.5 and 10.2 μm when using biogenic sulfide and chemical Na 2S, respectively, indicating that both sulfide sources are adequate for solid–liquid separation by sedimentation. When biogenic sulfide instead of chemical Na 2S was used, the efficiency of the ZnS precipitation process slightly decreased both in terms of zinc effluent concentration (at pS 10 and 20) and particle size of the precipitate (at pS 10, 15 and 20). This was shown to be attributed to the presence of various substances (phosphate, micro-nutrients, acetate, EDTA) present in the sulfate-reducing reactor effluent.

Dispersion and re-deposition of fine particles and their effects on saturated hydraulic conductivity

Measurements of saturated hydraulic conductivity (K) have been used to study the rates of structural breakdown and pore clogging which occurred during leaching of 2 contrasting soils, Balkuling agricultural soil and a mining residue. Soil columns were leached with solutions of different electrolyte concentrations under saturated conditions using a Marriotte constant-head device. Measurements were made with either abrupt change of concentration from 500 to 1 mmol/L or gradual decreasing concentration from 500 through 100, 50, 10, to 1 mmol/L of NaCl followed by deionised water. The relative hydraulic conductivity (K/Ko) decreased substantially with time and with decrease in electrolyte concentrations for both soils. The decreases were attributed to various extents of internal swelling, dispersion, and decreases of pore radii as a result of detachment followed by re-deposition of the clay fraction during leaching. There was little difference in ultimate reductions in permeability between the abrupt and gradual changes of concentration from 500 to 1 mmol/L for both soils. The mining residue was clearly more prone to structural deterioration than the agricultural soil. Whereas the effluent particles from the Balkuling soil included domains or aggregates of clay crystals, those from the mining residue columns appeared to consist essentially of primary clay crystals indicating the less cohesive nature of this disturbed material. We also estimated the extent of permeability reductions using theoretical investigations based on particle size distribution. Predicted simulations agreed reasonably well with experimental data for both soils following column leaching with 1 mmol/L, with the best agreement observed for the mining residue.

A fast inverse solver for the filtration function for flow of water with particles in porous media

Models for deep bed filtration in the injection of seawater with solid inclusions depend on an empirical filtration function that represents the rate of particle retention. This function must be calculated indirectly from experimental measurements of other quantities. The practical petroleum engineering purpose is to predict injectivity loss in the porous rock around wells. In this work, we determine the filtration function from the effluent particle concentration history measured in laboratory tests knowing the inlet particle concentration. The recovery procedure is based on solving a functional equation derived from the model equations. Well-posedness of the numerical procedure is discussed. Numerical results are shown.