What Actually Moves Your Cost per Cubic Metre of Leachate

Ask three contractors for a cost per cubic metre on the same leachate and you will get three numbers spread by a factor of two. Almost none of the difference sits in the price of the polymer. It sits in what each of them quietly assumed about dose, haul distance, rework and how much water they would be adding.

Start With a Cost Stack, Not a Price

A typical on-site job breaks down roughly like this: polymer 55-70% of the total, haulage 15-25%, labour and plant 10-15%, testing and administration 3-5%, and rework — the loads that come back or get re-dosed — anywhere from zero to 20% depending on how disciplined the site is. That last line is the one nobody puts in the quote.

At a dose of 1 kg per 40 L, a cubic metre needs about 25 kg of polymer. Halve the absorption performance — a saltier leachate, an old stock of powder, a grade matched to the wrong duty — and you have doubled the largest line in the stack. No amount of negotiating on the bag price recovers that.

The Five Real Drivers

Ionic strength comes first. Conductivity above roughly 25 mS/cm starts to cost real money, because the gel’s ability to swell is suppressed by the surrounding ions. Two cells on the same site can differ by 40% in dose purely on age and cover condition. This is measurable in ten minutes with a handheld meter and it is the first thing to check when a budget overruns.

Haul distance and weight come second. You are paying to move water. Every 1% of extra water in the load is 1% of extra tonnage across every kilometre. Over-dosing by 15% to be safe adds mass as well as polymer, so the penalty is paid twice — once at the bag, once at the weighbridge.

Third is the water you add yourself. A pre-mix slurry at 1% polymer is 99% water, and that water goes into the drum and onto the truck. On a 10 m3 batch dosed with 2 m3 of slurry, you have added 2 m3 of clean water to a waste stream you will be charged to dispose of. Some of it is unavoidable; a 3% slurry instead of 1% cuts the added volume by two thirds and is usually still pumpable.

Fourth is batch size and the rework rate. Small batches mean more cleaning, more wash water and more operator judgement per cubic metre. Below about 2 m3 per event, handling cost per cubic metre rises steeply regardless of polymer price. Rework is worse: a rejected load costs the original dose, the haul both ways, and the re-dose.

Fifth is testing frequency. Cheap compared with the rest, and the cheapest insurance in the stack. A weekly cup test and a conductivity reading costs almost nothing and catches the drift that produces rework.

How to Compare Two Quotes Properly

Ask each contractor for four numbers: dose rate in kg per cubic metre, expected absorption in L/kg at the site’s measured conductivity, added water volume per cubic metre, and the rework allowance they have priced. A quote at a lower cost per cubic metre with an unstated 20% rework allowance is not cheaper; it is a quote with a hole in it. Then ask what happens if the liquid changes mid-project — who carries that risk, and at what threshold does the rate get renegotiated.

The limit worth stating plainly: cost per cubic metre is the wrong unit for comparing solidification against biological or membrane treatment. Those alternatives have completely different volume reduction and residue profiles, and their cost sits in energy and membranes rather than polymer and trucks. Compare cost per tonne of material actually leaving site, and compare it over a full year, not a single campaign.

We publish absorption ranges against conductivity bands so that the first line of the cost stack can be estimated before you tender, on the SAP powder product range.