Municipal Wastewater
Getting more out of a works that cannot get bigger — chemically enhanced primary treatment, tertiary polishing to tight nutrient consents, and wet-weather capacity without new tankage.
The problem is usually space, not chemistry
Most municipal works needing intensified clarification are not failing because the chemistry is difficult. They are failing because the population grew, the consent tightened, or the storm flow got worse — and the site boundary did not move.
High-rate separation is the direct answer to that. A clarifier that occupies a fifth to a tenth of the conventional plan area for the same duty means capacity can be added inside the existing fence line, and in many cases inside existing tanks.
Chemically enhanced primary treatment
Dosing coagulant and polymer ahead of high-rate primary settling raises suspended solids removal from the 50–60 % typical of plain sedimentation to 80–90 %, and takes 40–60 % of the BOD out with it. That has two effects worth having: the biological stage receives a much lighter organic load, which frees aeration capacity and often defers an activated sludge extension; and more of the carbon is captured as primary sludge, which is a better feedstock for anaerobic digestion than the same carbon oxidised in an aeration basin.
Tertiary polishing and phosphorus removal
For consents in the 0.5–1 mg/L range, high-rate clarification with a single coagulant dose is normally sufficient. Below 0.1 mg/L the margin gets thin and the case for magnetite ballasting becomes strong: total phosphorus below 0.05 mg/L and suspended solids below 2 mg/L are achievable without a downstream filtration stage, which is often the difference between a scheme that fits on the site and one that does not.
Works uprating
Where an existing circular or rectangular clarifier is hydraulically limiting, magnetite ballasting can frequently multiply its throughput several-fold with no change to the tank itself — the added equipment is dosing, two reaction tanks, a shear mixer and a recovery drum. The comparison to make is against the cost of a new clarifier and the civil works that come with it.
| Design parameter | Typical range |
|---|---|
| CEPT suspended solids removal | 80–90 % |
| CEPT BOD removal | 40–60 % |
| Primary clarifier rise rate | 25–60 m/h |
| Tertiary clarifier rise rate | 20–40 m/h |
| Tertiary effluent TSS | < 5–10 mg/L (< 2 mg/L with KWS-MAG) |
| Tertiary effluent total phosphorus | < 0.1 mg/L; < 0.05 mg/L with KWS-MAG |
| Coagulant | Ferric chloride / sulphate, alum or PACl |
| Typical coagulant dose | 30–120 mg/L as product, water dependent |
| Polymer dose | 0.3–1.5 mg/L anionic |
| Primary sludge concentration | 2–4 % DS with KWS-HRC |
Doses and removals depend strongly on wastewater strength and alkalinity, and are confirmed by jar testing on your own influent.
Average and peak flow, influent BOD, COD, TSS and total phosphorus with their variability, the discharge consent, and a site plan or the dimensions of the tanks you want to reuse. That is enough for a platform recommendation and an indicative footprint.
Uprating a municipal works?
Send the flows, the influent analysis and the consent. We will tell you what fits inside the site you have.