At what pH is calcium carbonate more likely to precipitate out of solution in a water treatment system?

Calcium carbonate is more likely to precipitate out of solution at a pH of 8, as this is closer to the neutral to slightly alkaline range where calcium carbonate solubility decreases.

Source: Water treatment engineering fundamentals

What type of system has a higher fouling or scaling potential when operated on identical feed water?

A system with a higher concentration of scaling ions or particulate matter has a higher fouling/scaling potential. This is due to the increased likelihood of precipitation and deposition of solids on the membrane surface, which can lead to reduced system performance and increased maintenance requirements. The type of system that would experience higher fouling/scaling potential would be one with a higher recovery rate or without adequate pretreatment, such as coagulation, sedimentation, or filtration, to remove particulate matter and reduce scaling ion concentrations.

Source: Standard reverse osmosis system design principles

What factors must be determined to predict the scaling potential of a reverse osmosis unit?

To predict the scaling potential of an RO unit, several factors including the Langelier Saturation Index, Ryznar Stability Index, and the concentrations of scaling ions such as calcium and magnesium must be determined. Additionally, other factors like pH, temperature, and the recovery rate of the RO system also play a crucial role in determining the scaling potential.

Source: Water treatment engineering fundamentals

How is the Silt Density Index (SDI) calculated when given the initial and final plug times, and what does it represent in the context of reverse osmosis pretreatment?

The SDI is calculated as 1.0 / (T2 - T1) * (T / T1) * 100, where T1 and T2 are the initial and final plug times in seconds, and T is the total test time in minutes. Given T1 = 30 seconds, T2 = 60 seconds, and T = 15 minutes, the SDI would be 1.0 / (60 - 30) * (15 / 0.5) * 100 = 3.3, indicating the likelihood of fouling in a reverse osmosis system.

Source: Standard reverse osmosis system design principles

What is the typical method for removing cation-anion scalants in a water treatment system?

Cation-anion scalants can be removed by using an acid to dissolve the scale, as the acid can break down and solubilize the scaling compounds, allowing for their removal from the system.

Source: Water treatment engineering fundamentals

What type of reverse osmosis system configuration has a higher fouling and scaling potential when operated on identical feed water?

A system with a higher recovery rate or a system without adequate pretreatment has a higher fouling and scaling potential. This is because higher recovery rates concentrate impurities, increasing the likelihood of scaling, and inadequate pretreatment fails to remove foulants, leading to membrane fouling.

Source: Standard reverse osmosis system design principles

How are organic compounds removed using activated carbon in water treatment?

Organic compounds are removed within molecular-sized pores of activated carbon granules, where they are adsorbed due to van der Waals forces and other intermolecular interactions.

Source: Physical chemistry principles of aqueous systems