Ppm Silica Research Articles

The Impact of Silica Addition on Floc Volume Density in the Biofloc System for Juvenile Red Tilapia (Oreochromis niloticus)

Biofloc technology is a solution to the problem of waste management in aquaculture. Biofloc systems are beneficial because they not only reduce inorganic nitrogen waste from feed residues and fish excrement but also produce flocs. The aim of this research is to determine the effect of silica addition on floc volume density in the biofloc system for juvenile red tilapia. The research was conducted from January to March 2024 at the Center of Excellence in Science and Technology (PUI-PT) for Functional Nano Powder at Padjadjaran University. This study uses a Completely Randomized Design (CRD) experimental method with four treatments and three replications. The treatments used were (A) control, (B) 15 ppm silica, (C) 20 ppm silica, and (D) 25 ppm silica. The study used cylindrical containers with a capacity of 19 liters filled with 15 liters of water, a stocking density of 10 juvenile red tilapia per cylinder, with the juvenile measuring 3-4 cm and weighing 3-4 g. The parameters observed were floc volume density and water quality. The data on floc volume density and water quality were analyzed descriptively. The results showed that the addition of 25 ppm silica in the biofloc system was the best treatment for floc volume density. This was evidenced by the results in treatment D (25 ppm) achieving a floc volume density of 26.5 ml/L, which falls into the dense category. Therefore, the addition of silica concentration in the biofloc system can increase floc volume density.

Quantitation of Silica Contents in Lung Explants of Transplanted Patients: Artificial Stone-Induced Silicosis vs. Idiopathic Pulmonary Fibrosis.

Spectrophotometric techniques provide qualitative but not quantitative data on lung particles. We aimed to quantitate silica content in biopsies of lung-transplanted silicosis patients by applying X-ray fluorescence (XRF) spectrometry. Lung biopsies of 17 lung-transplanted artificial patients were quantitated for silica and other minerals particles by Niton XL3 XRF spectrometry. Occupational and clinical history data were assessed. Lung biopsies of artificial stone-induced silicosis (ASIS) patients contained significantly higher levels of silica compared to those of idiopathic pulmonary fibrosis (IPF) patients (7284.29 ± 4693.75 ppm vs. 898.88 ± 365.66 ppm, p < 0.0001). Silica content correlated negatively with age, body mass index, and pulmonary function test results. A 1128 ppm silica cut-off value yielded 100% sensitivity and 94% specificity for predicting ASIS (AUC = 0.94, p < 0.0001). In conclusion, XRF measurements in lung biopsies can differentiate between silica and mineral particles in ASIS and IPF.

A new model for silicification of cyanobacteria in Proterozoic tidal flats.

Microbial fossils preserved by early diagenetic chert provide a window into the Proterozoic biosphere, but seawater chemistry, microbial processes, and the interactions between microbes and the environment that contributed to this preservation are not well constrained. Here, we use fossilization experiments to explore the processes that preserve marine cyanobacterial biofilms by the precipitation of amorphous silica in a seawater medium that is analogous to Proterozoic seawater. These experiments demonstrate that the exceptional silicification of benthic marine cyanobacteria analogous to the oldest diagnostic cyanobacterial fossils requires interactions among extracellular polymeric substances (EPS), photosynthetically induced pH changes, magnesium cations (Mg2+ ), and >70ppm silica.

Employing logistic model to predict the egg production of quails receiving digestibility enhancer supplementation

This study aimed to predict the egg production of quails supplemented with a combination of betaine and silica+. Three hundred and fifty laying quails were divided into two dietary treatments and seven replicates of 25 quails. The treatments consisted of control (T0), and supplementation with digestibility enhancer mixture consisted of 0.12% betaine and 200 ppm silica+ (T1). Egg production data were collected for three periods of 28 days, and they were subjected to T-test. The data were plotted to obtain the egg production curve. A logistic regression model was employed to identify the trend of the egg production pattern. The T1 groups produced more eggs than T0 groups (P<0.05), which attributed to the higher egg production during period II and III (P<0.01). The egg production curves indicated that production rose sharply soon after the beginning of lay. The T1 groups had a higher peak production than T0 (76.43% vs 69.20%). Furthermore, production rate was 0.17 and 0.18 and prediction accuracy was 97% and 98% for T0 and T1, respectively. Thus, the logistic model proved to be employed to analyse the biological impact of egg production in quails with a high prediction accuracy.

Agronomic and Physiological Response of Rice Plant to Application of Silica from Different Sources

Aims: The research aimed to study the response of agronomy and physiology of rice plant to different silica sources.&#x0D; Study Design: Completely randomized design.&#x0D; Place and Duration of Study: The research was conducted in screen house of Faculty of Agriculture, Andalas University, Padang, Indonesia from April to December 2018.&#x0D; Methodology: Completely randomized design was used in the assay. The treatment was 10 Si sources (No silica, Si 1 ppm, Si 2 ppm, Si 3 ppm, husk charcoal 50 g/plant, husk charcoal 100 g/plant, husk charcoal 150 g/plant, husk ash 50 g/plant, husk ash 100 g/plant, husk ash 150 g/plant). The variety was Anak Daro. Each treatment was replied 3 times so that 30 experimental units were obtained. The data was analysed by using F test in 5% and followed by Duncan’s Multiple Range Test (DNMRT) in 5%. The data analysis using software Statistic Tool for Agricultural Research (STAR).&#x0D; Results: Silica sources affected the agronomic and physiological characters of rice plant. 2,3 ppm of silica, 100 and 150 g of husk charcoal and 100 g of husk ash were the best silica source for plant height. 3 ppm silica affected the number of tiller of rice plant. In number of chlorophyll, 150 g of husk ash affected the number of chlorophyll A and the silica sources did not affect the number of chlorophyll B.&#x0D; Conclusion: The sources of silica affected the agronomic and physiological response of rice plant which can be useful for rice cultivation in the region.

The impacts of silica nanoparticles coupled with low-salinity water on wettability and interfacial tension: Experiments on a carbonate core

Two main reservoir mechanisms that impact oil recovery factors are wettability alteration and interfacial tension (IFT) change. In this study, these two key mechanisms are evaluated experimentally for samples from the Asmari (carbonate) oil reservoir utilizing silica nanoparticles in the presence of low-salinity water. The nanofluid, rock formation and crude oil samples were prepared meticulously to ensure meaningful experimental could be conducted over a range of low-salinity conditions. The results show that across the range of salinities studied, the absolute value of zeta potential of nanofluids decreases with increasing total dissolved solids (TDS) in the water treated with silica nanoparticles interacting with the formation samples. This indicates that increasing the salinity, decreases the stability of the low-concentration (<2000 ppm) silica nanofluids studied. The results of the IFT and wettability alteration experiments for silica-particle nanofluids on this carbonate reservoir suggest that: 1) by increasing the concentration of nano-silica, IFT generally decreases; 2) IFT increases when TDS of the water increases.; 3) contact angle alteration becomes more significant as the concentration of nano silica increases, resulting in significant changes in the reservoir rock’s wettability towards more water-wet conditions; 4) contact angle alteration decreases as TDS of the water increases; and, 5) minimum IFT (about 14.29 dyne/cm) occurred at 5000 ppm nano-silica concentration and salinity of 9000 ppm, whereas the maximum degree of wettability alteration (about 126.2 degree) occurred at 5000 ppm nano-silica concentration and salinity of 1000 ppm.

Silica accumulation rates for siliceous sinter at Orakei Korako geothermal field, Taupo Volcanic Zone, New Zealand

The rate of silica accumulation on glass slides over 895 days (2 years 5 months and 12 days) was determined using in-situ experiments in the discharge channel of Map of Australia hot pool, located at Orakei Korako, Taupo Volcanic Zone (TVZ), New Zealand. The discharge channel consisted of constantly flowing alkali chloride water with a temperature of 75 °C, pH of 7, 269 ppm silica, a flow rate of 1.4 l/s and mass flow of 1.36 kg/s. One slide was placed parallel to the flow, while another slide was perpendicular to the flow direction. Amorphous silica (opal-A spheres) deposited on both slides to form abiotic, sub-aerial, lily-pad textures which grew on basal sub-aqueous sinter structures. Lily-pad sinter forms by capillary motion of the water reaching and wetting the sub-aerial sinter surface, where the silica accretes to previously formed sinter surfaces parallel to the pool water level. In our experiment, silica deposition was greater in the horizontal direction than the vertical direction. Silica accumulation was up to four times greater on the front face of each slide. The maximum vertical and horizontal growth rates of sinter observed in our experiment were 3.9 and 7.6 mm/year, respectively. The observation that very little sinter grows below the water line is consistent with most of the sinter precipitating as a result of cycles of wetting, evaporation and drying. Quantitative calculations show that the observed growth rates are within the maximum amount of sinter expected to be deposited by evaporation. These measurements provide a constraint on the mass flow and time required to form siliceous sinter deposits of a known thickness, at extinct hot spring sites. Better constraining siliceous sinter growth rates improves our understanding and reconstruction of paleo-hydrological hot spring conditions.

The Mutual Effect of Irrigation Scheduling and Foliar Spray of Silica Nanoparticles on Basil Plant

Afield experiment was conducted during 2016 and 2017 in the Research Farm of Sakha Agricultural Research Station, Kafr El-Sheikh Governorate, Egypt to evaluate the mutual effect of irrigation scheduling and silica nanoparticles on Ocimum basilicum L. vegetative growth, yield, chemical composition and some water relations. Irrigation scheduling treatments were 1.2, 1.0 and 0.8 of cumulative pan evaporation (CPE) while a foliar spray of silica nanoparticles at 30, 60, 90 ppm and distilled water as a control. Results showed that 0.8 of CPE decreased vegetative growth characters, fresh and oil yield ha-1 and transpiration rate nevertheless, increased chlorophyll content, oil% and stomatal resistance value in the two cuts of both seasons. Silica nanoparticles at 60 and 90 ppm increased all characters likely oil yield increased by 52.2% over the control. Irrigation at 1.0 of CPE with silica nanoparticles at 60 ppm recorded the highest values of vegetative growth, fresh and oil yield, chlorophyll content and oil%. The highest essential oil components were α –terpineol and linalool in plants sprayed with 60 and 90 ppm silica nanoparticles under all irrigation treatments. The greatest values of seasonal consumptive use and applied irrigation water were observed from plants treated with 1.2 of CPE while, the lowest values obtained from 0.8 of CPE. The highest values of productivity of irrigation water and water productivity were recorded after 1.0 of CPE. Finally, plants treated with 1.0 of CPE combined with silica nanoparticles at 60 ppm showed enhanced vegetative growth, fresh and oil yield, stomatal resistance value, oil components while, decreased transpiration rate. Furthermore, decreased water consumptive use 7% and applied irrigation water 5% while, increased water productivity by 24% and productivity of irrigation water by 20 % compared to 1.2 of CPE without silica nanoparticles spray.

CCD series no-16: opened vs. closed circuit SWRO batch desalination for volume reduction of Silica containing effluents under super-saturation conditions

Opened-circuit desalination (OCD) of a high salinity source (>10,000 ppm) also containing large amounts of Silica (>124 ppm) by the application of a single-element module batch apparatus under the conditions of fixed applied pressure of declined flux at low pH was reported to proceed with 80–85% recovery by a high-energy process of low permeate productivity through high super-saturation conditions of silica. The present study describes theoretical model simulations of OCD and closed-circuit desalination (CCD) processes of same feed source (10,000 ppm NaCl–125 ppm SiO2) with different apparatus of identical single-element (SWC6-MAX) modules which execute either closed- or opened-circuit desalination under fixed pressure (47 bar) of variable flow conditions. The results of this theoretical study reveal milder batch process conditions for CCD compared with OCD manifested by longer sequence duration (23.35 instead of 15.95 min), much lower energy consumption (1.57 instead of 7.93 kWh/m3) with average TDS of permeates about the same for both processes up to ~75% batch recovery, and higher for the former process (531 instead of 316 ppm TDS) at the ultimate batch recovery of both (~83%) with same pattern also repeated for the average Silica content in permeates (6.76 instead of 3.65 ppm silica). Silica in the recycled concentrates of both CCD and OCD processes is found in the range of 125–728 ± 6 ppm) and reveals desalination under high super-saturation conditions with Silica maximum of ~5.8-fold (~580%) excess over its ordinary saturation level.

Passive Q-switched Erbium-doped fiber laser with graphene–polyethylene oxide saturable absorber in three different gain media

A Q-switched Erbium-doped fiber laser (EDFL) is proposed and demonstrated using graphene/polyethylene oxide thin film as a passive saturable absorber. The multi-layered graphene saturable absorber is incorporated into ring cavity of EDFL. Three different gain media are tested for the EDFL and they are 7 m long silica Erbium-doped fiber (EDF) with 400 ppm Erbium concentration, 4.5 m long EDF with 2,000 ppm Erbium concentration and 0.5 m long Bismuth EDF with 3,000 ppm Erbium concentration. The threshold pump powers for stable and seft-starting Q-switching are 33.7, 98.5 and 59.5 mW for 400, 2,000 and 3,000 ppm EDF, respectively. Corresponding pulse repetition rates are 24.2, 9.8 and 22.5 kHz at the threshold pump powers. The shortest pulse width of 2.48 μs is obtained with EDFL configured with 0.5 m long Bismuth EDF. The highest pulse energy of 40.69 nJ is obtained at pump power of 98.5 using 2,000 ppm silica EDF.

규산과 질소형태별 처리에 따른 벼의 수분 및 질소흡수와 이용효율 비교

2001년 국립식량과학원 인공기상실에서 수경재배로 규산의 시용 여부가 영양생장기 벼의 수분과 질소흡수량에 미치는 효과를 조사하여 규산시용 여부 및 공급된 질소의 형태별 처리에 의한 시험품종들의 수분과 질소이용효율을 산출한 결과는 다음과 같다. 1. 처리 67일 후의 벼 건물중은 규산처리 시험구 및 <TEX>$NH_4+NO_3$</TEX> 혼합시용 처리구가 규산을 처리하지 않은 시험구 및 NH4 단독시용 처리구보다 유의하게 증가하였음. 2. 이앙 후 67일간 조사된 벼의 수분흡수량은 규산처리와 규산 무처리 간의 차이가 없었으나 질소흡수량은 규산 무처리에 비해 규산처리구에서 유의하게 증가하였음. 3. 질소형태별로는 <TEX>$NH_4$</TEX> 단독 시용보다<TEX>$NH_4+NO_3$</TEX> 혼합시용에서 규산처리 여부와 관계없이 수분과 질소흡수량이 월등히 많았음. 4. 수분이용효율은 규산처리 시험구가 규산을 처리하지 않은 시험구에 비해 유의하게 증가하였으나 질소형태별 처리에서는 차이가 없었음. 5. 질소형태의 혼합처리가 암모늄태 단독처리보다 질소 흡수량은 유의하게 많았으나 질소이용효율은 감소하였음. This experiment was carried out to elucidate the effects of silicate and different application forms of N on the uptake of water and N by rice plants. Three rice cultivars, Ilpum, Anda and M202, were grown under the hydroponics in a phytotron. One-hundred ppm silica was applied for silicate treatment. For nitrogen application forms were 100% <TEX>$NH_4$</TEX> and <TEX>$NH_4+NO_3$</TEX> in 2:1 ratio were applied. Silica treatment, compared to silica free, was very effective on the nitrogen uptake and dry weight increase of rice plants. Although silica application demonstrated no significant effect on the amount of water uptake, it improved increased water and nitrogen use efficiency. Therefore, sufficient application of silicate in paddy field will be useful for the growth of rice plants and water saving.

PH modification for silica control

ABSTRACT Lowering solution pH slows the polymerization of silica and formation of silica scale. In batch systems, lowering the pH of approximately 200 ppm silica solutions prevents scale formation for over 300 h. Silica scale forms most quickly near pH 8. Solutions with pH 3.6–3.7 can maintain silica levels of 1,000–3,000 ppm for roughly 90 h. Bench-scale membrane testing showed that silica scale formation lag times of approximately 72 h were achievable after lowering the pH to 4.5–4.7, which might allow flushing of silica-laden solutions through, for example, flow reversal, before scale formation occurs during water treatment.

Additive-Driven Dissolution Enhancement of Colloidal Silica. 1. Basic Principles and Relevance to Water Treatment

The effect of various chemical additives (small molecules and polymers) on the dissolution of two kinds of colloidal silica (Aerosil 200 and laboratory-synthesized, SSD) is systematically studied at pH 10. The silica scale dissolvers tested are 5-carboxybenzotriazole (CBZT), amino-tris(methylene phosphonic acid) (AMP), a phosphino-polycarboxylic acid (PPCA), diethylenetriamine pentacarboxylic acid (DETPA), a proprietary polymer (Genesol 40), poly(acrylic acid) (PAA), ethylenediamine-tetrakis(methylenephosphonic acid) (EDTMP), phosphonobutane-1,2,4-tricarboxylic acid (PBTC), sodium metaborate, and N-phosphonomethylimino-diacetic acid (PMIDA). Of the polymeric additives only Genesol 40 shows some dissolution activity, dissolving ∼280 ppm silica at 10 000 ppm dosage after 72 h. PBTC and DETPA are the best-performing additives of all those tested. PBTC is effective even at the 2500 ppm dosage, as it solubilizes ∼290 ppm silica after 72 h. Its efficiency is dosage-dependent. DETPA is also an effective silica d...

炭素繊維電極への微生物の電気的吸着に及ぼすシリカの影響

We have considered a method to collect and sterilize bacteria using a positively-charged carbon fiber electrode. The feature of this method is that it can sterilize spores, which could not be sterilized by heating or bactericidal agents. However, the capacity to collect Bacillus subtilis spores decreased in the silica solution. To investigate this matter, we measured the effective surface area and bacteria affinity of the carbon fiber dipped in 100 ppm silica solution for 24 hr, and investigated the method to improve the collecting capacity. The results were as follows. The surface coverage of silica was 57%, calculated from the weight change, or 53%, calculated from the electrolytic current change. The zeta potential of the carbon fiber decreased from −11 mV to −15 mV, and Bacillus subtilis spores were not adsorbed into the carbon fiber on their own. When a constant cathodic current of 1 A was applied to the carbon fiber, the capacity to collect the Bacillus subtilis spores increased from 88.05% to 99.88%, and the surface coverage of silica was about 5%. Therefore, it was considered that silica was dissolved in water, and the capacity to collect bacteria could be recovered.

The simulated silicification of bacteria--new clues to the modes and timing of bacterial preservation and implications for the search for extraterrestrial microfossils.

Evidence of microbial life on Earth has been found in siliceous rock formations throughout the geological and fossil record. To understand the mechanisms of silicification and thus improve our search patterns for evidence of fossil microbial life in rocks, a series of controlled laboratory experiments were designed to simulate the silicification of microorganisms. The bacterial strains Pseudomonas fluorescens and Desulphovibrio indonensis were exposed to silicifying media. The experiments were designed to determine how exposure time to silicifying solutions and to silicifying solutions of different Si concentration affect the fossilization of microbial biofilms. The silicified biofilms were analyzed using transmission electron microscopy (TEM) in combination with energy-dispersive spectroscopy. Both bacterial species showed evidence of silicification after 24 h in 1,000 ppm silica solution, although D. indonensis was less prone to silicification. The degree of silicification of individual cells of the same sample varied, though such variations decreased with increasing exposure time. High Si concentration resulted in better preservation of cellular detail; the Si concentration was more important than the duration in Si solution. Even though no evidence of amorphous silica precipitation was observed, bacterial cells became permineralized. High-resolution TEM analysis revealed nanometer-sized crystallites characterized by lattice fringe-spacings that match the (10-11) d-spacing of quartz formed within bacterial cell walls after 1 week in 5,000 ppm silica solution. The mechanisms of silicification under controlled laboratory conditions and the implication for silicification in natural environments are discussed, along with the relevance of our findings in the search for early life on Earth and extraterrestrial life.

The Effect of Post-Treatment of a High-Velocity Oxy-Fuel Ni-Cr-Mo-Si-B Coating Part 2: Erosion-Corrosion Behavior

In this paper, a study of the erosion-corrosion characteristics of a Ni-Cr-Mo-Si-B coating applied by the high-velocity oxy-fuel (HVOF) process on to an austenitic stainless steel (UNS S31603) substrate are reported. The coatings were studied in the as-sprayed condition, after vacuum sealing with polymer impregnation and after vacuum furnace fusion. The erosion-corrosion characteristics were assessed in an impinging liquid jet of 3.5% NaCl solution at 18 °C at a velocity of 17 m/s at normal incidence in two conditions: (1) free from added solids and (2) containing 800 ppm silica sand. The methodology employed electrochemical control and monitoring to facilitate the identification of the separate and interrelated erosion and corrosion contributions to the erosion-corrosion process. The rates of erosion-corrosion damage were drastically accelerated in the presence of the suspended solids. The application of cathodic protection significantly reduced the deterioration process. The study showed the effect of sealing with polymer impregnation did not significantly alter the erosion-corrosion behavior of the sprayed coating. However, there was a significant improvement in erosion-corrosion durability afforded by the postfusion process. The mechanisms by which the improved performance of vacuum-fused coatings is achieved are discussed.

Effect of Silicate on Passive Films Anodically Formed on Iron in Alkaline Solution as Studied by Electrochemical Impedance Spectroscopy

Abstract Studies using electrochemical impedance spectroscopy (EIS) were carried out on an iron disk electrode in 0.01 mol/L sodium hydroxide (NaOH) + x ppm silica (SiO2) (x = 250, 500, and 750 ppm...

Optimizing chemical treatment of a power plant water softener

The Piñon Pine Plant of Sierra Pacific Power Company near Reno, Nevada is a zero discharge facility. To maintain zero discharge operation a side-stream softener is used to control circulating cooling water (circ-water) and discharge pond water quality. During plant startup, this softener was not performing to its design objectives, which specified maximums of 30 ppm calcium as Ca, 10 ppm magnesium as Mg, and 20 ppm silica as SiO2 in the softened water. Jar tests were conducted to determine the best chemicals and optimum dosages for the side-stream softener. The optimum pH range for softening was in the range of 11.3–11.5. Replacing the Polyaluminum Hydroxychlorosulfate (PAC) coagulant with 25–50 mg/L of Mg(OH)2 greatly improved flocculation. In addition to Mg(OH)2 solution, MgSO4 was required at a dosage of 50 mg/L as Mg to reduce the silica concentration to 20 mg/L as SiO2. The optimum dosage of Na2CO3 (soda ash) was 750 mg/L to reduce the calcium concentration to 30 mg/L as Ca. The optimum dosage of flocculent (a Polyacrylamide based anionic polymer) was 10–15 mg/L. Dispersant addition was adversely effecting the softening process.

Optimizing chemical treatment of a power plant water softener

The Pitton Pine Plant of Sierra Pacific Power Company near Reno, Nevada is a zero discharge facility. To maintain zero discharge operation a side-stream softener is used to control circulating cooling water (circ-water) and discharge pond water quality. During plant startup, this softener was not performing to its design objectives, which specified maximums of 30 ppm calcium as Ca, 10 ppm magnesium as Mg, and 20 ppm silica as SiO2 in the softened water. Jar tests were conducted to determine the best chemicals and optimum dosages for the side-stream softener. The optimum pH range for softening was in the range of 11.3–11.5. Replacing the Polyaluminum Hydroxychlorosulfate (PAC) coagulant with 25–50 mg/L of Mg(OH)2 greatly improved flocculation. In addition to Mg(OH)2 solution, MgSO4 was required at a dosage of 50 mg/L as Mg to reduce the silica concentration to 20 mg/L as SiO2. The optimum dosage of Na2CO3 (soda ash) was 750 mg/L to reduce the calcium concentration to 30 mg/L as Ca. The optimum dosage of flocculent (a Polyacrylamide based anionic polymer) was 10–15 mg/L. Dispersant addition was adversely effecting the softening process.

The effect of home water softeners: Added sodium may be hazardous to your health

The Pitton Pine Plant of Sierra Pacific Power Company near Reno, Nevada is a zero discharge facility. To maintain zero discharge operation a side-stream softener is used to control circulating cooling water (circ-water) and discharge pond water quality. During plant startup, this softener was not performing to its design objectives, which specified maximums of 30 ppm calcium as Ca, 10 ppm magnesium as Mg, and 20 ppm silica as SiO2 in the softened water. Jar tests were conducted to determine the best chemicals and optimum dosages for the side-stream softener. The optimum pH range for softening was in the range of 11.3–11.5. Replacing the Polyaluminum Hydroxychlorosulfate (PAC) coagulant with 25–50 mg/L of Mg(OH)2 greatly improved flocculation. In addition to Mg(OH)2 solution, MgSO4 was required at a dosage of 50 mg/L as Mg to reduce the silica concentration to 20 mg/L as SiO2. The optimum dosage of Na2CO3 (soda ash) was 750 mg/L to reduce the calcium concentration to 30 mg/L as Ca. The optimum dosage of flocculent (a Polyacrylamide based anionic polymer) was 10–15 mg/L. Dispersant addition was adversely effecting the softening process.