We treat portions of the sample with various coagulants to determine which performs best for floc formation, settling rate, and supernatant clarity. Coagulants include chemicals such as ferric chloride, aluminum sulfate (alum), polyaluminum chlorides (PACl), and cationic polymers.
Discover How Jar Testing Can Provide Treatment Guidance
Jar testing allows us to decide which chemicals and their optimal dosages are needed to improve water clarity and remove colloidal solids. We also perform jar tests to determine the ideal chemical treatment to meet regulatory limits. Our lab uses a Phipps & Bird, six-jar stirrer to perform the jar testing.
Coagulation occurs when a sample is treated with a positive charged chemical that neutralizes the negative charge on solid particles. By neutralizing the charge, the particles can join, or coagulate, and form larger particles that settle more quickly than the smaller, charged particles.
Once a coagulant has been chosen and an optimum dose determined, we treat portions of the sample with different coagulant doses. We then compare the settling characteristics of the sample treated with the different dosages.
Flocculant Screening and Dosing
Once we have determined the optimum coagulant dosage, the sample may need a polymer flocculant to improve the settling rate and supernatant clarity. To determine the optimum flocculant, we treat sample portions with the coagulant and then perform a polymer screening on the coagulated solids.
Lime softening is used to soften hard water to prevent scaling in pipes and tanks. The process raises the pH of a slurry by mixing it with hydrated lime (Ca(OH)2) to precipitate calcium and magnesium ions. This reduces the hardness and/or alkalinity of the slurry. Raising the pH through lime softening can also precipitate other ions.
Ballasted flocculation is usually needed when the solids in a sample are too fine or light to settle quickly, even with coagulation and flocculation. Adding a fine sand, or some other seed particle, and a flocculant to a feed slurry produces a ballasted floc. Mixing the slurry with coagulants/polymers and the ballasted floc sand causes the smaller particles attached to the sand to produce larger, heavier particles that settle quickly and leave a clearer supernatant.
Ballasted Floc Dosing
We determine the amount of sand, or seed, and flocculant needed to settle the solids by jar testing. We test various doses of seed with the previously determined chemical treatment. We then compare the settling rate and supernatant clarity results from each dose and use the optimal seed dose in further testing.
Solids Contact Clarification Testing
Solids contact clarification is similar to ballasted floc because solids are added to the feed slurry to act as a seed to improve the solids removal and settling. However, instead of a separate source for the seed, a solids contact clarifier recycles the solids in the underflow to seed the slurry feed. We can determine the mass of solids that need to be recycled for the feed slurry, and then size a clarifier with sedimentation testing.
High Density Sludge Testing
High density sludge (HDS) testing is accomplished by mixing hydrated lime with a portion of previously precipitated solids, raising the pH, then mixing this with the acid water to be treated. The key to this is achieving a pH that will precipitate the metal ions present in the acid water. Mixing the previously precipitated solids with hydrated lime creates a seed that precipitating metal ions can form on. This process results in shorter reaction times for metals removal, reduced super saturation, and a slurry with much better thickening and filtration characteristics.
Through pH adjustment and other chemical treatments, many metals, metalloids, and even a few non-metals can be precipitated and removed from a slurry. Metals such as calcium and magnesium are precipitated through lime softening to reduce the hardness and/or alkalinity of a slurry. Other slurries may have toxic or hazardous levels of some metals such as lead, nickel and zinc, or metalloids such as arsenic or selenium. pH adjustment can precipitate these elements, and filtration or thickening can remove the precipitated solids.
- AltaFlo™ High-Rate Thickener
- CONTRAFLO® Solids Contact Clarifier
- Conventional Clarifier
- Conventional Gravity Thickener
- Deep Bed™ Paste Thickener
- Flocculating Clarifier
- HiDensity™ Paste Thickener
- HiFlo™ High-Rate Thickener
- RapiSand™ Ballasted Flocculation
- RapiSand Plus™ Package Treatment Plant
- Solids CONTACT CLARIFIER™
- SuperSettler™ Inclined Plate Clarifier
- Titan™ Traction Thickener
- Trident® HS Package Water Treatment Plant
- Trident® HSC Package Water Treatment Plant
- Trident® HSR Package Water Treatment Plant
- Trident® Package Water Treatment Plant
Other Testing Solutions
Lab testing helps determine chemical pretreatment, percent recycle, float layer solids concentration, and subnatant clarity.
This service helps you determine precoat material, filter cloth, filter cake moisture, polymer screen, and filtrate clarity.
We provide guidance on equipment decisions related to thickening and clarification.