Selection of medical waste treatment technologies

The choice of treatment system is contextual and involves consideration of:

• Relevant national and international regulations and requirements

• Environmental and occupational safety factors

• Waste characteristics and quantity

• Technology capabilities and requirements

• Cost considerations

• Operation and maintenance requirements

The characteristics and quantity of waste generated will vary according to the type or level of facility, between rural and urban areas, according to differences in services provided, scale, organizational complexity, availability of resources, and the number of clinical and non-clinical staff. Regulations or policies on waste classification as well as segregation practices affect waste generation rates. Furthermore, the quantity of waste that must be treated depends on whether waste is destroyed at a facility (decentralized treatment) or if waste from several health facilities is combined for treatment (centralized treatment). “Green procurement” (e.g. sourcing commodities with less packaging and/or reduced use of materials) can also reduce the amount of overall waste.

If a new treatment technology is needed, it is essential to know the predicted quantity of waste that will be generated to select the appropriate technology. To calculate the quantity of waste, average waste generation rates are calculated on a weekly basis to account for daily variations in a given week and lower activities at weekends. However, data are often provided in kilograms (kg) per day or kg per year. Kilograms per occupied bed per day and kg per outpatient per day are used to compare health care facilities with different levels of activities. If inpatient occupancy rates and the daily number of outpatients are not available, the total number of beds is often used to estimate kg of waste per bed per day.

The following table provides estimates than can be used to calculate infectious waste generation in low and middle-income countries when local data are not available. There is large variability in the volume of waste generated at a single type of facility and thus a facility assessment of waste is highly recommended before selecting a treatment technology.

Infectious health care waste rates

Based on the amount of infectious and sharp waste generated, the required capacity of the waste treatment technology can be calculated. The waste generation rate per day should be multiplied by the average number of patients per day or number of beds x bed occupancy rate.

Examples: Calculation of quantity of infectious waste generated and required treatment capacity

1. Hospital

Assumptions:

• 100 bed hospital; 100% bed occupancy rate (BOR); 1-hour cycle time, 6 hours waste treatment per day; 7 treatment days per week; 0.5 kg infectious waste per bed per day.

Calculation:

• 100 beds x 100% (BOR) x 0.5kg /bed/day x 1.2 (safety margin) = 60 kg infectious waste per day

• 60 kg/6 working hours =10 kg per hour

Result:

This hospital needs a technology with a minimum treatment capacity of 10 kg per hour.

2. Clinic (primary health care facility – outpatients only)

Assumptions:

• 10 patients per day, 0.07 kg infectious waste per patient, maximum storage of infectious waste: 2 days (48 hours).

Calculation:

• 10 patients x 0.07 kg/patient x 1.2 (safety margin) = 0.84 kg infectious waste per day

• 2 days of storage x 0.84 kg per day = 1.68 kg every two days

Result:

This clinic needs a technology with a minimum treatment capacity of 2 kg (every two days).

Note: It takes low and middle-income countries for instance.

A safety margin of 20% should be added to the total to cover fluctuations in waste generation rates. The amount of waste generated per day (kg/day) should be divided by the number of working hours per day of the waste treatment equipment to achieve the minimum treatment capacity needed (kg/h). If the treatment technology is only operated on specific days (e.g. Monday to Friday) the required capacity can be adapted. The cycle time of treatment technology is defined as the time needed for adding in waste, treating, and removing waste. An additional hour for the start-up of the treatment system should be considered.

Examples of annual operation costs of water and electricity:

Hospital with 100 beds using an alternative non-incineration technology for the treatment of infectious and sharp waste.

Assumptions:

• Non-incineration technology: 10 kg per cycle and 21,900 kg waste per year

• Manufacturer’s data: 5 kWh average electricity consumption per cycle and 50 litres of water consumption per cycle

Example 1:

• Costs of consumables for the hospital: 0.1 USD per kWh and 1.0 USD per cubic meter water (1 m³ = 1000 litre; 1 litre costs 0.001 USD).

Calculation of electricity and water costs:

• Electricity and water costs of 1 cycle:

» (5 kW x 0.75 h/cycle x 0.1 USD/kWh) + (50 l/cycle x 0.001 USD/l) = 0.375 USD/

cycle + 0.05 USD/cycle = 0.425 USD/cycle

• Costs of the treatment of 1 kg of waste:

» 0.425 USD/10 kg = 0.0425 USD/kg

• Cost per year:

» 0.0425 USD/kg x 21,900 kg = 930.75 USD

Example 2:

• Water is trucked to the hospital and electricity is generated by a diesel generator

• Costs of consumables for the hospital: 2 USD per kWh and 0.5 USD per cubic meter water (1 m³ = 1000 litre; 1 litre costs 0.0005 USD).

Calculation of electricity and water costs:

• Electricity and water costs of 1 cycle:

» (5 kW x 0.75 h/cycle x 2.00 USD/kWh) + (50 l/cycle x 0.0005 USD/l)

» = 7.50 USD/cycle + 0.025 USD/cycle = 7.525 USD/cycle

• Costs of the treatment of 1 kg of waste:

» 7.525 USD/10 kg = 0.7525 USD/kg

• Cost per year:

» 0.7525 USD/kg x 21,900 kg = 16,479.75 USD

Result: The annual operation cost of the selected treatment technology for water and electricity for example 1 is 930.75 USD per year and for example 2 is 16,479.75

The capital cost and annual operation and maintenance cost of the technology must also be considered. Capital costs cover the equipment purchase including taxes, costs associated with shipment (including customs fees), insurance, site preparation (including provision of water, electricity and waste water drainage) and indirect costs like project management, architecture and engineering, permits and legal fees (UNEP 2012a).

Operation costs include labour, spare parts, waste bags/containers, electricity, water, fuel and waste disposal. The annual operation costs of consumables like water, electricity and fuel are based on:

• the consumption of the selected treatment option

• the number of cycles needed to treat the generated waste amount and

• the total cost of all consumables.

Maintenance and repair of treatment technologies are essential to ensure optimal operation. Maintenance requirements vary considerably according to the type of technology used and the

manufacturer. The annual maintenance costs are estimated at 3-5% of the investment costs of the treatment technology. A detailed maintenance schedule should be provided by the manufacturer during commissioning and as part of operator training. When purchasing new equipment, provision for sufficient warranty time (at least 1 year) should be included, as well as essential and most commonly needed spare parts. Consumables kits should be easily accessible in-country. Proper user training, including basic maintenance and process validation and efficiency test kits (if applicable), should be provided by the manufacturer, an authorized service company or by the technician/operator of the treatment equipment.

Note: After selection of a waste treatment equipment, the end users must accept responsibility for addressing future maintenance, repair and infrastructure needs of the selected waste treatment equipment as specified by the vendor/manufacturer.

Medical waste treatment autoclave

Medical waste treatment autoclave