HTH Calcium Hypochlorite for Large-Scale Camp Water Treatment: A Field Guide for WASH Teams in DRC and Uganda

A WASH coordinator managing a new displacement camp in Kyangwali or Nakivale does not have the luxury of waiting for chlorine supplies to clear Mombasa port and travel upcountry. With an average of 2,500 new refugees arriving in Uganda each week — the vast majority fleeing the Democratic Republic of Congo — the window between site assessment and the first water distribution is often less than 72 hours. The question of which disinfectant to specify, how much to order, and how to dose it correctly must be answered before the emergency begins, not after.

The DRC cholera outbreak, declared the country's worst in 25 years, has recorded 64,427 cases and 1,888 deaths since the start of 2025, according to UNICEF. As Congolese refugees cross into Uganda and South Sudan, they bring with them the epidemiological risk profile of an active transmission zone. Cholera incubation takes hours to days. Water system failure at the entry point of a transit camp can seed an outbreak before humanitarian agencies have completed their initial needs assessment.

HTH calcium hypochlorite granules — available in 45 kg drums — are the workhorse disinfectant for large-scale camp water treatment. This guide explains why, how to dose correctly, and what field teams need to know before the first truck arrives at the distribution point.

Quick answers for field teams:

• HTH calcium hypochlorite (65–70% available chlorine) is effective at 0.5 mg/L FRC at the point of distribution under normal conditions; during active cholera transmission, raise the target to 1.0 mg/L FRC at the source

• A standard 45 kg drum at 65% available chlorine treats approximately 585,000 litres of water to a 1 mg/L dose — enough to supply roughly 29,000 person-days at the Sphere minimum of 20 L/person/day

• Sphere Handbook minimum for emergency water supply is 15 L/person/day; UNHCR operational target is 20 L/person/day

• Always test free residual chlorine at the distribution point and at household level — never rely on source-dose calculations alone

Why Calcium Hypochlorite Outperforms Alternatives at Camp Scale

Three disinfectant options are used across humanitarian WASH programmes: sodium hypochlorite solution (liquid chlorine), point-of-use tablets such as Aquatabs, and calcium hypochlorite granules or powder. Each has its place, but for treatment of bulk water volumes at new displacement camps, calcium hypochlorite has operational advantages that matter in the field.

Sodium hypochlorite solution degrades rapidly — typically losing 20–30% of its active chlorine within 30 days in tropical storage conditions. Transporting liquid chlorine in bulk from Kampala or Juba to remote sites requires specialist containers and cold chain management. Aquatabs and similar tablets are the correct tool for household-level point-of-use treatment and for distribution to dispersed populations where centralised treatment is not yet functional. They are not designed to treat 100,000-litre bladder tank systems.

Calcium hypochlorite granules at 65–70% available chlorine retain potency for 12–18 months when stored in sealed drums in a dry, shaded environment. A single 45 kg drum is compact enough to transport by light vehicle and carries sufficient active ingredient to treat volumes that would require hundreds of litres of equivalent sodium hypochlorite solution. The WHO technical note on measuring chlorine in water supplies confirms that calcium hypochlorite is among the most practical options for emergency bulk disinfection precisely because of this stability and concentration advantage.

For WASH procurement managers working under IOM Core Pipeline or UNICEF supply arrangements, calcium hypochlorite also offers a cost-per-litre-treated advantage over liquid alternatives once transport and storage losses are factored in. Specialized Logistics Solutions (SLS) holds stock of HTH calcium hypochlorite drums in Juba and Kampala, available without the six-to-eight week lead times that international procurement entails.

Dosing Calculations: What Field Teams Get Wrong

The most common field error is calculating chlorine dose at source and assuming that figure holds across the distribution system. It does not. In hot, high-turbidity conditions typical of eastern DRC and northern Uganda settlement sites, free residual chlorine (FRC) at the point of collection can fall to zero within hours of treatment, even when the source reading appeared compliant.

The Sphere Handbook sets the standard at 0.2–0.5 mg/L FRC at the point of delivery. The WASH Cluster guidance on chlorination specifies 0.5 mg/L at the filling point during normal conditions, rising to 2 mg/L when cholera risk is present — with the intent of arriving at 0.2 mg/L or above at the household tap or collection point. Peer-reviewed research published in the Journal of Water and Health recommends targeting 1.0 mg/L FRC at the source in high-temperature settings as the minimum threshold to deliver measurable residual protection after distribution lag.

Working calculation for field teams:

• Determine daily volume: population × 20 L/person/day (UNHCR target)

• Determine dose: 1 mg/L = 1 gram per cubic metre (1,000 litres)

• Account for chlorine demand of raw water: test with a jar test or demand test if turbidity is above 5 NTU — in high-turbidity conditions, chlorine demand can absorb 3–5 mg/L before residual protection begins

• Calculate gross dose: demand + target residual + distribution loss estimate

• Dissolve granules in a small volume of clean water to form a stock solution before adding to the tank — never add granules directly to the bulk distribution system

For a 10,000-litre bladder tank targeting 2 mg/L at source, the gross dose is 20 grams of 100%-active chlorine equivalent. At 65% available chlorine, the actual granule weight required is approximately 31 grams per tank fill. This scales linearly: a site running four 10,000-litre tanks through two fill cycles daily requires approximately 248 grams of granules per day — or roughly one 45 kg drum every 180 operating days at that scale.

These are estimates. Every site has a different raw water chlorine demand. Field teams should conduct daily FRC monitoring at the source, at the distribution point, and at a sample of household collection points. The MSF Medical Guidelines on water supply during cholera response provide a practical chlorine demand-testing protocol suitable for camp conditions.

The DRC–Uganda Corridor: Why Pre-Positioned Stock Matters

Uganda currently hosts more than 1.5 million refugees, the vast majority from DRC and South Sudan. UNHCR reports that the country's open-door policy is under sustained pressure from the speed and scale of new arrivals driven by the conflict in eastern Congo. Nakivale Refugee Settlement — one of Africa's largest — hosts approximately 190,000 people, and its current latrine-to-person ratio is reported at 1:107, more than double the humanitarian standard. Water access constraints are acute.

New arrivals from eastern DRC carry the risk profile of an active cholera zone. The UNICEF regional appeal for Eastern and Southern Africa notes that cholera cases in the region rose more than seven times in the first six weeks of 2026 compared with the same period in 2025, driven by flooding, displacement, and damaged WASH infrastructure. The May rainy season — now underway across Uganda, South Sudan, and eastern DRC — historically accelerates transmission by overwhelming fragile water and sanitation systems.

For WASH teams receiving new population arrivals into transit or reception camps, the operational question is not whether to chlorinate but how fast the supply chain can deliver compliant stock. International procurement routes from Mombasa to western Uganda involve minimum lead times of 21–28 days under favourable conditions. When the security situation in eastern DRC deteriorates, road access from Kenya through Uganda becomes the only viable corridor, and competition for trucking increases across all humanitarian agencies simultaneously.

Pre-positioned stock in Kampala — available for same-day or next-day dispatch to settlement sites in western and south-western Uganda — eliminates this bottleneck. Specialized Logistics Solutions (SLS) supplies WASH products including HTH calcium hypochlorite from regional warehouses with 35+ years of in-country logistics experience across Uganda, South Sudan, Kenya, and DRC. UNGM-registered (Vendor No. 380716), SLS is a recognised supplier to IOM, UNHCR, UNICEF, WHO, and major NGO partners operating in the region.

Storage, Safety, and Handling in Field Conditions

Calcium hypochlorite is a strong oxidising agent. Improper storage causes accelerating degradation, fire risk if the granules contact organic material, and contamination of adjacent food or pharmaceutical supplies. Field teams handling HTH drums need to observe the following non-negotiable protocols.

Store drums upright in a dedicated chemical store, separate from fuel, food, medical supplies, and NFI items. The store must be dry, shaded, and ventilated — direct sunlight and high temperatures accelerate active chlorine loss. Partially used drums must be resealed with the original lid immediately after use; exposure to humid air triggers decomposition and generates toxic chlorine gas in enclosed spaces.

Personal protective equipment for handling includes chemical-resistant gloves, eye protection, and a face mask rated for chlorine vapour. Granules should never be handled with wet hands or poured into containers that still hold water — always add the chemical to water, not water to concentrated granules. This order of operations prevents violent spattering.

The Oxfam guidelines for water treatment in emergencies, widely adopted across the WASH Cluster, provide a full handling and storage protocol for calcium hypochlorite that should be built into field team induction materials.

Shelf life at correct storage conditions is 12–18 months from manufacture date. Teams procuring stock in Kampala or Juba should verify the manufacture date on delivery and plan consumption schedules accordingly. SLS supplies drums from current production batches and can provide documentation on available chlorine percentage on request.

Integrating HTH into a Camp WASH System

Calcium hypochlorite granules do not operate in isolation. A functioning camp water treatment system pairs bulk disinfectant with appropriate storage and distribution infrastructure. The two most common configurations in Uganda and South Sudan are bladder-tank systems fed by water trucking, and gravity-fed systems from treated surface or borehole sources.

In a trucked-water bladder system, treatment occurs at the filling point before water is distributed to communal taps. The dosing station should be positioned at the bladder fill inlet, with the stock chlorine solution metered in using a calibrated dosing pump or a simple drip-feed arrangement timed against fill volume. FRC should be tested 30 minutes after dosing before distribution begins. At a UNHCR emergency water standard of 20 L/person/day, a camp of 5,000 people requires 100,000 litres of treated water daily — approximately ten fills of a 10,000-litre bladder tank.

For pumps and equipment needed to fill tanks from surface water sources, SLS stocks Multiquip and Aussie Pumps units alongside water treatment chemicals, allowing a single procurement order to cover both the extraction and treatment components of a new site setup.

What This Means for Your Programme

DRC's cholera emergency is moving across borders. Uganda's refugee settlements are under pressure. The May rainy season is compressing the operational window for establishing compliant water supply before transmission risk peaks. The time to confirm chemical stock is not when the first cases are reported — it is now.

Calcium hypochlorite at 65–70% available chlorine remains the most practical bulk disinfectant for large-scale camp treatment in East and Central Africa. Correct dosing, daily FRC monitoring, and compliant storage convert a potentially deadly gap in WASH coverage into a manageable field operation.

Specialized Logistics Solutions (SLS) holds pre-positioned stock of HTH calcium hypochlorite drums in Juba and Kampala, available for rapid dispatch. Contact the team at sales@maji-safi.org.

Frequently Asked Questions

What is the correct dose of calcium hypochlorite for cholera response in a camp setting?

During active cholera transmission, the WASH Cluster recommends targeting 2 mg/L free residual chlorine (FRC) at the filling station, with the goal of maintaining at least 0.2 mg/L at the point of household collection. At 65% available chlorine, this requires approximately 3.1 grams of HTH granules per 1,000 litres treated, adjusted upward based on the chlorine demand of the raw source water.

How long does calcium hypochlorite last in storage?

At 65–70% available chlorine, properly sealed HTH drums stored in a cool, dry, shaded environment retain their potency for 12–18 months from the manufacture date. Exposure to moisture, direct sunlight, or high temperatures accelerates degradation. Always verify the manufacture date on delivery and monitor for loss of the characteristic chlorine odour, which can indicate degraded product.

Can I use calcium hypochlorite granules for point-of-use treatment at household level?

Calcium hypochlorite granules are designed for centralised bulk treatment of large volumes, not household use. For household-level point-of-use treatment, Aquatabs 67mg tablets — for which Specialized Logistics Solutions (SLS) is an authorised distributor — provide a safer, pre-measured dosing option that eliminates the risk of handling error at community level.

What is the minimum water quantity standard for emergency camps?

The Sphere Handbook sets the emergency minimum at 15 litres per person per day for all uses. UNHCR's operational planning standard for refugee camps is 20 litres per person per day. Both figures assume treated water meeting WHO drinking-water quality guidelines, including a measurable FRC at the point of collection.

How do I test free residual chlorine in the field?

FRC testing requires a calibrated colorimetric or digital chlorine meter using DPD (N,N-diethyl-p-phenylenediamine) reagents. Pool test strips are not sufficiently sensitive or accurate for WASH monitoring purposes. The WHO recommends testing at the source, at the distribution point, and at a random sample of household collection containers at least once daily during active cholera transmission.