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Tertiary treatment

Advanced cleaning of wastewater that goes beyond the secondary or biological stage, removing nutrients such as phosphorus, nitrogen, and most BOD and suspended solids.


Total Hardness. The sum of calcium and magnesium hardness, expressed as a calcium carbonate equivalent.


Trihalomethanes, by-products of chlorination.

Total Dissolved Solids (TDS)

The concentration of dissolved solids in a wastewater or effluent, ie the residue after evaporation and drying, expressed in milligrams per litre of sample.

Total solids

All the solids in wastewater or sewage water, including suspended solids and filterable solids.

Trade effluent

Wastewater produced by trade and industry; not domestic sewage.

Transfer (water)

System where drinking water or raw water is moved around a region.


The ability of an aquifer to transmit water.


The process by which water vapour is released into the atmosphere after transpiring of living plants.

Treatment works

A processing site used by a water company to take water from a river or underground source and make it safe to drink.

Trickling filter

A wastewater treatment unit that contains medium material with bacteria. The stream of wastewater is trickled over the medium and the bacteria break down the organic wastes. Bacteria are collected on the filter medium.

Trunk sewer

A sewer which receives many tributary branches or discharges from other large sewers and serves a large area.


Total Solids. The weight of all present solids per unit volume of water. It is usually determined by evaporation. The total weight concerns both dissolved and suspended organic and inorganic matter.


Interference with the passage of light rays through a liquid, caused by the presence of suspended matter.

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