Tertiary polishing carbon for industrial and municipal effluent — colour, chemical oxygen demand and refractory organics taken out ahead of discharge or reuse.
Everything upstream decides whether the bed lasts a year or a month.
Industrial effluent carries a narrow but concentrated set of organics, often coloured, often refractory to biological treatment. The carbon is there for exactly that fraction. Where solids, oil or an unstable biological stage reach the bed instead, capacity is consumed by material that a filter or a clarifier should have taken out, and the changeout interval collapses.
55–75
% COD reduction
Typical tertiary polishing performance on a correctly pre-treated effluent.
The carbon is one stage in a train, not the whole of it.
The existing train is assessed before any carbon is specified. Solids, oil and biological stability at the carbon inlet decide whether a bed is viable at all.
The actual effluent is run against candidate grades, since competing organics in a real effluent behave nothing like a single-compound isotherm.
Contact time is set longer than potable duty because the load is heavier and the molecules larger, with backwash frequency matched to the solids that still arrive.
Spent carbon is removed on a monitored breakthrough and routed to reactivation or licensed disposal according to what it has adsorbed.
The grades that fit wastewater treatment — and what each is good at.
Coal based · 8x30, 12x40
Broad pore distribution for high-molecular-weight organics and colour, with the hardness to survive frequent backwashing on a solids-bearing feed.
Lignite and coal blends
Dosed into an activated sludge or clarification stage to absorb shock loads and toxicity without a dedicated vessel.
High hardness · reactivable
Specified where spent carbon volumes justify thermal reactivation, so the same fill returns to service several times rather than to landfill.
What each property actually governs once the bed is running.
The mesopore indicator, and the figure that governs where colour and large refractory molecules dominate the load.
Capacity for the smaller fraction of the load. Read alongside the molasses number rather than on its own in effluent duty.
Effluent beds are backwashed hard and often. Hardness decides how much of the fill survives to the end of the cycle.
Sets carbon mass per vessel and the backwash rate needed to expand the bed and lift the accumulated solids.
Longer than potable duty. Large, slowly diffusing molecules need the additional residence to reach the internal surface.
Rarely constraining in discharge duty, but it matters where the treated effluent is being recovered for reuse in process.
At the end, after solids removal, oil separation and biological treatment. It is a polishing stage for what nothing upstream can remove, and putting it earlier converts an adsorbent into an expensive filter.
Typically twenty to forty minutes empty bed contact time, considerably longer than drinking water duty, because the molecules are larger and diffuse into the granule more slowly. The figure is confirmed on the actual effluent by column test.
Almost always suspended solids or oil arriving at the bed. Carbon has no capacity for either; they accumulate in the void space, drive head loss up and shorten the run long before the adsorption capacity is exhausted.
It depends on volume and on what has been adsorbed. Above a certain annual tonnage the economics are clear, but carbon loaded with certain regulated substances may be excluded from reactivation and must go to licensed disposal instead.
Within limits, and better than most stages, because a bed buffers concentration swings. Genuine step changes in composition still need to be characterised, since a grade chosen for one organic profile may be poorly matched to another.
Send the effluent analysis at the carbon inlet, the consent to be met and the upstream train, and we will come back with the grade, the bed size and the changeout interval.
