What is the correct pH for the jar test procedure?
· Its small scale nature allows operators to test a variety of chemical dosing and mixing parameters to evaluate their impact on the effectiveness of coagulation. After a jar test has been completed, operators will test the water in the jars for turbidity, pH, alkalinity, organics, and other parameters that may be key to coagulation process control.
What type of water should be used for jar test?
Add 1 or 2 drops of coagulant solution. Mix at high speed for 1 to 3 minutes. Turn off mixer and observe the coagulation (agglomeration) of the precipitated particles.
What is a jar test for coagulants?
· Using a clean 1-mL syringe, add 0.1-mL of the 100% solution of each coagulant being tested. Mix for two minutes at medium speed. Add 0.10-mL of aluminum sulfate or existing inorganic metal salt coagulant. Mix for one minute at medium speed, after stopping the mixer, look for small particles in the wastewater referred to as “microfloc particles.”
What is a successful jar testing procedure?
After 5 minutes of settling: Place syringe ~1/2-in below surface and pull in 25 mL of water over a time period of 12 seconds (25 mL/12 sec). Jar Test - Filterability Test. Syringe ~ 25 mL from jar (after 5 minutes of settling) Attached filter holder housing 1.2 um membrane filter to syringe.
What is the best pH for a jar test?
A jar test procedure as described above can help to establish the optimum pH within the 7.5 to 11 range. For adjusting pH, sodium hydroxide is recommended. However, other common chemicals can be used — such as soda ash and lime. For some applications (nickel complexes) magnesium hydroxide is an effective reagent.
How does coagulant work in wastewater?
Adding coagulants to the wastewater creates a chemical reaction in which the repulsive electrical charges surrounding colloidal particles are neutralized, allowing the particles to stick together creating clumps or flocs. The aggregation of these particles into larger flocs permits their separation from solution by sedimentation, flotation, filtration or straining. When required, flocculants with an anionic charge are commonly used to facilitate the agglomeration of the flocs and their settling.
What is the function of cationic polymers in precipitants?
Some precipitants contain cationic polymers that neutralize the precipitated particles. The cations (positive charges) from the polymer reduce or reverse the negative charges of the precipitate which, in turn, permits the coagulation and flocculation of the particles.
What is the insoluble particle formed by adding a precipitating reagent to a wastewater solution?
The suspended stability of such particles is due to both their small size and to the electrical charge (usually negative) on their surface causing them to repel their neighboring particles.
What is the effect of low solubility on precipitants?
These precipitants, with low solubility, can achieve very high removal efficiencies. When used as a “polishing” precipitant, the dosage of a precipitant can be lowered depending on the quantity of metals that are precipitated as hydroxides by pH adjustment.
Why is pH important?
That is, dissolved heavy metal ions can be precipitated chemically by adjusting the pH of a wastewater stream. The pH is important because all metals have a pH at which their solubility is minimal.
How long does it take for a precipitating reaction to be complete?
Please note that, although the precipitating reactions appear to be instantaneous, a retention time of up to 15 minutes may be required to obtain a complete reaction.
What is a coagulant jar?
Coagulant Jar testing on your wastewater is a useful method in determining the correct product to fit your company needs . By jar testing on a sample of wastewater generated from your production line, significant benefits emerge such as product compatibility and validation, correct chemical dose and injection rate, and projected use-cost. Below we lay out how to jar test coagulants and flocculants in 9 simple steps.
How long to mix a coagulant?
Using a clean 1-mL syringe, add 0.1-mL of the 100% solution of each coagulant being tested. Mix for two minutes at medium speed.
How long to mix anionic flocculant solution?
Set the mixer to a low speed, using a clean 1 mL syringe, add 1 mL of existing anionic flocculant solution to each beaker, mix for one minute.
How long to settle water in a jar?
Assign a designated cuvette for each jar. After 25 minutes of settling, quickly dip cuvette below surface to fill. Do this for each jar and measure settled water turbidity.
How fast should you paddle a coagulant?
Fill jars with source water prior to coagulant injection and set paddle speed at 30 rpm
How long to slow mix a jar of flc?
Slow mix for 5 minutes (30 rpm for 1 liter jars, up to 40 rpm for 2 liter jars), (10 minutes for delay floc formation)
How to remove bubbles from NTU?
Micro bubbles can adhered to glass causing false NTU readings. To remove bubbles, tilt cuvette up to 90 degrees.
How long does it take for a floc to work?
Floc up to 10 Minutes when Needed
How much of plant off line for filter media change out?
50% of plant off-line for filter media change out
What is UV absorbance?
UVA – UV absorbance is calculated as a relative measure of the amount of light absorbed by a water sample compared with the amount of light absorbed by a pure water sample.
Which coagulant has the highest filtered sulphate?
As expected, the sulphate-containing coagulant, PAX-XL52 had the highest level of filtered sulphate, while the other two coagulants had similar filtered sulphate levels.
Does coagulant increase chloride levels?
Therefore, adding coagulant to water may increase the levels of chloride and/or sulphate in the finished water. In this study, all selected coagulants contain chloride in their major ingredients, and PAX-XL52 contains sulphate. Ontario and Health Canada have the same AOs for both chloride and sulphate of 250 mg/L and 500 mg/L, respectively (MECP, 2006; Health Canada, 1987; Health Canada, 1994). The filtered chloride and filtered sulphate results are shown in Figure 6.
Why do plants need jar testing?
Jar testing is beneficial for plants so that they can optimize their treatment process
Which turbidity corresponds to the lowest TOC?
With the Ferric, the lowest turbidity corresponded to the lowest TOC and lowest UV (and the plant would have met the TOC removal regulation)
Is there a difference in TOC between 20 and 30 ppm?
There was no difference in TOC between the 20 and 30 ppm Ferric dosages – a plant could get the same TOC removal with less chemical
Is 20 ppm alum the same as 30 ppm?
20 and 30 ppm Alum dosage had the same turbidity, but there was slightly better TOC removal with the 30 ppm But…
Does alum have the same turbidity?
20 and 30 ppm Alum dosage had the same turbidity, but the TOC went down with the 30 ppm (even though UV went up)
Is UV a good indicator of TOC removal?
Spoiler alert: turbidity and UV were not always the best indicator of optimum TOC removal
What to do after flocculation and settling?
After flocculation and settling, sample the settled water to determine which coagulant dose was best
How effective is coagulation in water treatment?
150 times more effectively than when they received water from a coagulation process that was not optimized. Effective coagulation not only improves pathogen removal in the sedimentation basin, but in the filters, as well. And the degree of improvement demonstrated in Dugan’s study is huge. When the coagulant dose is optimized, there will, most likely, be less subsequent pH adjustment required to stabilize the finished water pH at an acceptable level. Further, with fewer particles in the filtered water, one may reasonably expect that the oxidant demand of the water would be less, so smaller disinfectant doses may be required. Therefore, efficient coagulation, flocculation, and sedimentation can also make multiple treatment processes more cost effective.
What is representative jar testing?
Representative jar testing means that the jar test procedure will imitate the coagulation, flocculation, and settling conducted in the water plant. There is no single jar test procedure will duplicate all of these processes for all plants, however, experience shows that jar test procedures can be individually tailored to accurately predict performance for almost every plant.
Which is key to effective sedimentation?
Figure 2: Good Coagulation is Key to Effective Sedimentation
Why do surface water treatment plants use a multi-barrier approach?
Because of the potential to transmit pathogens or other harmful constituents in surface water to the customers, surface water treatment plants (SWTPs) use a multi-barrier approach to remove and inactivate bacteria, viruses, and protozoa and protect public health. SWTP barriers . Removal and inactivation .
What is the purpose of surface water treatment?
The purpose of surface water treatment is to eliminate pathogens, which are microbes that can make people sick. Lakes and rivers are subject to contamination by numerous sources of pathogens, from septic fields to animal waste.
Why is surface water treated?
Because of the potential to transmit pathogens or other harm ful constituents in surface water to the customers, surface water treatment plants (SWTPs) use a multi-barrier approach to remove and inactivate bacteria, viruses, and protozoa and protect public health.
What are the barriers to water supply?
Very generally, as shown in Figure 1, these barriers include source water protection, coagulation-flocculation, sedimentation, filtration, disinfection, and distribution.
What happens when coagulants are added to water?
When metal coagulants are added to water, several hydrolysis species are formed. Some of these species are positively charged, depending primarily on water pH. These posi-tively charged species will attach to negatively charged particles and reduce or neu-tralize the particles’ negative charges. This charge neutralization results in a reduc-tion or elimination of the electric repulsion between particles. Cationic polyelectrolytes also can reduce the negative charges and repulsive forces. Note, however, that if the dosage of a cationic polymer is substantially greater than that needed to neutralize the negative charges on particles, then the particles can become positively charged and restabilized, a condition that hinders particle removal.
Why do we use positively charged metal coagulants?
Therefore, positively charged metal coagulants or polymers are used to decrease the extent of the negative surface charge on the particles so that when they come in contact with each other they can stick together and form larger particles (flocs).
What is the next step after coagulation?
The next treatment process after coagulation typically is flocculation. The main objec-tive of flocculation is to bring together the particle solids created and/or conditioned in the coagulation step, which ultimately changes the size distribution of the particles. Essentially, a large number of small particles are transformed into a smaller number of larger particles. Traditionally, the objective of flocculation has been to produce par-ticles large enough and dense enough to settle in the clarifier (sedimentation basin). Since the 1980s, several plants have replaced conventional sedimentation with filtra-tion without clarification (direct filtration) or dissolved air flotation (DAF). For these types of treatment processes, the goal of flocculation and floc size production is modi-fied since both of these processes work well with flocs that are considerably smaller than the size of flocs needed for sedimentation. For direct filtration and DAF plants, shorter flocculation times are used as compared to the times employed at plants with conventional sedimentation basins.
When polymers are added to water, what happens to the polymeric chains?
When high-molecular-weight polymers are added to water, part of the polymeric chains can attach to the surface of one particle with the remaining length of the chains extend-ing into the solution. If these extended chains find other particles with vacant sites not
What is NOM in water?
NOM is generally classified into two components: humic substances (HSs) and nonhumic substances (nHSs). HSs are usually the major components of NOM in water with humic acids (HAs) and fulvic acids (FAs) as the major fractions. The major fractions of nHSs are proteins, polysaccharides, and carboxylic acids.
What are the sizes of water particles?
Particle size may vary by several orders of magnitude. Most inor- ganic particles have sizes ranging from 0.1 to 5 micrometers (one-millionth of a meter, or μm). Figure 1-1 shows a comparison of sizes that may be encountered in water supplies. Biological particle size is dependent on the classification of the microorgan- ism. Viruses, for example, are the smallest biological particles and have sizes of 3–100 nanometers (one billionth of a meter, or nm). Bacteria are larger than viruses and have sizes from slightly less than 1 μm to over 10 μm. Algae and protozoan cysts are even bigger and have sizes from a few μm to a several hundred μm. Operators are often familiar with the terms colloidal/suspended particlesand sus- pended/dissolved solids. These terms are based on particle size and sometimes can be confusing. Colloidal particles are particles with at least one of their dimensions less than about 1 μm or 0.5 μm and generally are not filtered out in the suspended solids test. Dissolved solids contain both colloidal particles and the impurities that are in dissolved form. By definition, colloidal particles do not include constituents that are in true dis- solved or molecular form, which typically have sizes of less than 1 nm. Particle size is important in water treatment because it is one of the key factors in determining the settling characteristics of the particle. For example, the settling veloc- ity of a particle is directly proportional to the square of its diameter. Natural particles in the colloidal size range do not settle quickly enough to be removed in sedimentation basins, so they must be agglomerated together into larger particles, i.e., floc. The size of the floc particle is important for effective settling. Particles passing through the sedi- mentation process (and flocculated particles in direct filtration treatment plants) may be removed in the filtration process. Again, the size of the particle determines whether the particle will be removed in the top layer of the filter or will penetrate deeper into the filter bed.
What are oxidants used for?
Use of oxidants to change surface properties of particles . Use of oxidants prior to filtration has been shown to benefit filter performance at numerous plants. Reported benefits include a reduction in filtered water turbidity or particle counts or both, a decrease in turbidity peak during the filter ripening period, and a shorter dura- tion for filter ripening. Oxidants generally used for this purpose are free chlorine and ozone. However, other oxidants such as chlorine dioxide and potassium permanganate exhibit similar benefits. A recent study (Becker et al. 2004) indicated that one of the major mechanisms for these benefits is on the effect of oxidation on particle stability. As mentioned previously, most particles in water carry some kind of NOM coating on their