Sediment & Sludge

Sediment

Material that settles to the bottom of a liquid
Solid fragments of inorganic or organic material

Turbidity

Turbidity refers to suspended solids i.e. muddy water is very turbid.

Turbidity is undesirable for 3 reasons:-

Aesthetic considerations
May contain heavy metals, pathogens and other contaminants.
Turbidity degreases the effectiveness of water treatment techniques by shielding pathogens from chemical or thermal impairment, and in the case of UV treatment, absorbing the UV light itself. This effect is known as "shadowing" and allows bacteria to enter a system using microscopic debris as a shield against the light source.

It is important for re-circulating water to have as low turbidity (suspended solids) as possible.

Sludge

The three most common types of sludge's are coagulant / polymeric: chemical softening: and oxidized iron/manganese.

If a raw water source has a high concentration of Total Suspended Solids (TSS), the alum/iron coagulant sludge's will contain a high level of gelatinous hydroxide precipitants. Iron manganese sludge's will also tend to comprise of gelatinous hydroxide solids.

Chemical softening sludge's primarily consist of crystalline calcium carbonate with the magnesium hydroxide portion of the solids increasing as the magnesium content of the raw water increases.