What 500 g of Gel Powder Covers in a Field Sanitation Kit

The pouch is 500 g, the instruction card is laminated A6, and the bucket is a 20 litre jerry can with the top cut off. That is the sanitation module in a relief kit designed for a family of five for one week. Whether it is enough depends on three numbers that are never on the card: how many litres a person passes in a day, how much powder it takes per litre in that climate, and what happens when the powder runs out on day five.

This article works through the rationing arithmetic for field kits, the climate adjustments that catch agencies out, and the packaging choices that make 500 g last longer in practice than it does on paper.

The base arithmetic, and why it is optimistic

At 12 g per litre, 500 g treats 41 litres. A healthy adult passes 1.0 to 1.5 litres a day, so a family of five produces 5 to 7.5 litres a day, and one week needs 35 to 52 litres of treatment. The pouch covers a light week and fails a hot one.

Climate pushes the figure the wrong way twice. In 38 C heat, urine volume rises toward 2 litres a day per person for anyone drinking adequately, which is exactly what public health teams instruct. And concentrated urine, common when water is rationed, needs 15 to 18 g/L rather than 12. A hot, water-scarce setting can therefore double the requirement to 90 to 120 litres of treatment capacity per family-week.

Rationing by sachet rather than by scoop

The kits that work issue 10 g sachets in strips of ten, not a 500 g pouch with a scoop. Fifty sachets is a countable resource, and counting changes behaviour. A family can see that ten sachets is two days at five per day, and the strip can be hung on a nail inside the shelter where it stays dry.

Dose per use, not per litre, in the field. A 10 litre bucket filled to the 8 litre mark gets six sachets, which is 7.5 g/L and slightly under the ideal but adequate for a bucket that will be emptied within twelve hours. Under-dosing a little and emptying often beats over-dosing and leaving the bucket to stand.

What to do when the powder runs out

Every kit needs a documented fallback, because the powder will run out before the week does in a hot deployment. The cheapest fallback is a covered latrine with a soil or ash cover, which controls odour and flies without any polymer. The second is a shallow trench with daily covering, sited at least 30 metres from any water source and downwind of the shelter.

Write the fallback on the same card as the dosing instruction. A card that only describes the polymer teaches a family to depend on a supply that may not arrive, and the failure mode is a bucket left open in a living space.

Packaging that survives the first rain

Powder in a paper sachet inside a cardboard carton is a single rain event away from becoming a solid block. Specify foil or metallised film sachets with a 60 micron minimum, packed in a polyethylene bag inside the carton, and add a desiccant where the kit will be stored for more than six months. A 500 g pouch of clumped powder is functionally zero grams, and the family has no way to know until they open it.

Also specify a wide-mouth container. Dosing into a narrow-necked bottle in the dark, with a sachet torn by hand, spills a measurable share of a scarce resource. A cut-down jerry can with a lid costs almost nothing and saves perhaps 5 per cent of the supply.

The number to put on the procurement sheet

Litres treated per kilogram at the ambient temperature of the deployment, not at 20 C in a laboratory. Ask the supplier for the figure at 35 C, in 1.0 per cent saline, and multiply by 0.8 for field losses. For a standard grade that lands near 33 litres per kilo, which means a 500 g pouch is realistically 16 litres of treatment, or three days for a family of five.

Once that figure is on the sheet, the kit design decision becomes obvious: either double the pouch to 1 kg, or halve the assumed deployment from seven days to three and plan a resupply. Both are defensible. Assuming 41 litres and shipping 500 g is not.

For relief and field sanitation programmes we supply foil sachets from 10 g to 500 g in low-dust grades with hot-climate absorption data, and the pack specifications are at the SAP powder product range.