Strategic care: Finding an action plan for the disposal of medical waste

The proper disposal of healthcare waste remains an unresolved issue in many countries in different parts of the world. A range of treatment technologies are available, but before any of these options are adopted, medical facilities will need to assess the problem and devise a management strategy. by Ghassan Obid The treatment and disposal of medical waste - otherwise known as healthcare waste - is a problem facing both developed and developing countries throughout the world. The main sources of medical waste are obvious. They include hospitals (major generators) and smaller establishments such as health centres, medical clinics, laboratories, doctors’ surgeries and veterinary practices (minor generators). Less obvious is a clear system for handling this waste stream. Both developed and developing countries require new or improved regulations to combat this problem. This article describes five technologies used to treat medical waste and introduces an evaluation system for decision-makers who wish to compare these alternatives and select the best option for a specific site. Defining the problem The first step is to define the problem. In many countries, there is no clear definition of medical waste. As a result, potentially dangerous medical wastes (excluding pathological waste) can be collected together with municipal solid waste (MSW). Clear definitions accompanied by adequate staff training are required before separate collection of the different waste types will occur. Medical waste can be grouped in to the five categories shown in Table 1. References 1 and 2 provide further information. TABLE 1. Proposed definitions of medical waste Category Definition Recycling/disposal A - Domestic waste(non-recyclable) Non-recyclable domestic waste from administration, general cleaning, kitchens, and workshops.Also includes other general medical waste from hospitals and areas of external consultation. Disposal together withMSW A - Domestic waste(recyclable) Reusable and recyclable domestic waste from administration, kitchens, and workshops.Includes paper, plastic, glass and food waste. Recycling B - Infectious waste Waste expected to contain pathogens (bacteria, viruses, parasites or fungi) in sufficient concentration or quantity to cause disease in susceptible hosts. This includes: waste from infected patients in isolation wards (such as excreta, dressings from infected or surgical wounds, clothes heavily soiled with human blood or other body fluids) cultures from microbiological laboratories waste from surgery and autopsies on patients with infectious diseases (such as tissues, and materials or equipment that have been in contact with blood or other body fluids) animal bodies from experiments with contagious diseases and their excrements instruments or materials that have been in contact with infected persons or animals. Special treatment or disposal is required to prevent infections C - Sharps Discarded sharps, syringes, needles, infusion sets, cartridges, scalpels; knives, blades, small items of broken glass, other sharp instruments coming from hospitals and areas of external consultation. Special treatment or disposal required to prevent infections D - Pathological waste Pathological material such as human organs, tissues, placentas, fluids or parts of the human body from: • operating theatres • delivery rooms • surgeries • autopsies • pathology • morgues. Special treatment or disposal required to prevent infections E - Pharmaceutical,chemical and otherwaste types Waste originating from pharmacies, special treatment , laboratories and workshops, such as: pharmaceutical waste includes expired, unused, spilt, and contaminated pharmaceutical products, drugs, vaccines, and sera that are no longer required chemical waste (discarded solid, liquid and gaseous chemicals), such as from diagnostic and experimental work, cleaning, housekeeping and disinfection procedures other waste types including genotoxic waste, cytotoxic waste and radioactive waste. Treat/dispose of together with hazardous waste from industry How much waste is being generated? Information on the volume of medical waste generated by hospitals and other sources in a particular region or country tend to be available only for developed countries. That said, some individual hospitals in developing countries do estimate the amount of waste they generate. Dedicated surveys have attempted to assimilate the data available. The results from one such survey are shown in Table 2. TABLE 2. Medical waste generated per day (groups B, C and D). source: fichtner study2 Hospital Quantity, kg/bed/day Beijing, municipal hospital 0.15 Bogotá, Colombia 1.20 Buenos Aires, municipal hospital 0.20 Buenos Aires, private hospital 0.30 Germany, municipal hospital 0.05 Germany, University hospital 0.10 Ghana, University hospital 0.20 Thailand 0.23 Average of the survey of Western Java/Indonesia 0.30 The amount of medical waste generated differs not only from country to country but also within a country. The amount generated depends on numerous factors such as: segregation of domestic waste from other groups established waste management methods the type of medical establishment hospital specialization the proportion of reusable items employed in hospitals the proportion of patients treated on a day-care basis. My estimate is that 85%-95% of medical waste is domestic, 2%-5% covers infectious waste, sharps, or pathological waste and 3%-10% can be labelled as pharmaceutical, chemical, or other. Developing a management strategy Having defined the different types of medical waste, the next step is to develop a strategic plan for integrated management based on following principles or hierarchy: prevention/minimization recovery or recycling treatment and disposal.Medical waste prevention/minimizationIn common with most waste streams, the priority is to minimize the production of waste at source. This approach offers the only long-term solution for reducing waste quantities and disposal costs. Akin to recycling and recovery, it must be supported by educating the staff involved.Medical waste recovery/recyclingThere is potential to recycle a variety of materials from the ‘waste’ generated by healthcare and research facilities, including paper/cardboard, plastics, glass, metals, organic materials from kitchens, and some chemical wastes, such as developers and fixers. Food waste from wards should be excluded from recycling due to the potential for contact with pathogens or other contaminants.Medical waste treatment and disposalVarious technologies are available for the treatment and disposal of potentially infectious wastes (groups B, C in Table 1) and pathological wastes (group D). Their use can be controversial, particularly when the type chosen depends more on the economics of the system than on environmental performance. A typical medical waste incinerator. photo: san-i-pak Click here to enlarge image A lack of adequate funding remains a serious issue, particularly for publicly operated hospitals in middle- and low-income countries. Frequently the state provides more than 50% of services and budgets are stretched. As a result, managers naturally look at what offers the best performance for the money available.Different landfilling options have been developed. These include embedding the infectious waste in a landfill containing MSW, or constructing a separate, specialized landfill cell for infectious waste on the site of a municipal waste landfill. Most infectious agents do not have a long lifetime under landfill conditions.Traditionally many hospitals in western Europe and the US ran their own incinerators. This had the major advantages of disinfecting the medical wastes completely and reducing the amount of waste requiring transport and disposal elsewhere. However, this approach prompted concerns about mercury and dioxin emissions. Mercury emissions from medical waste incineration originate from thermometers, blood pressure gauges, batteries or amalgam that are discarded incorrectly as medical waste in the hospital. Dioxins are generated due to the presence of chlorine in the waste, caused by PVC and, in some countries, by chlorine used in chemical disinfection.The implementation of higher emission standards has increased the cost of running a waste incinerator, both in terms of labour and flue gas scrubbing. As a result, many of the small hospital incinerators in Europe and the US have been shut down.As smaller incineration plants have closed, so larger, centralized facilities have emerged. The US, which incinerates 85% of its medical waste, exemplifies this trend. Historically, US generators of medical waste relied on smaller plants to incinerate their waste. However, following regulations introduced by the Environmental Protection Agency (EPA) in 1997, many of these smaller plants have been replaced by centralized facilities.The new centralized plants, equipped with high-standard flue gas cleaning equipment, often serve a region with 10 million or more inhabitants and incinerate approximately 15-20 tonnes per day. However, the higher costs of using these facilities (particularly transport costs) are prompting hospitals to apply disinfection methods on their premises. The market share of thermal disinfection processes increased share during the 1980s and 1990s. Such processes can be found in the shape of decentralized facilities at large hospitals or, in some cases, as centralized plants. It is even possible to use mobile units, where the treatment plant comes to the waste rather than the other way around.The picture is clearly a complex one, so let us look at the options in greater detail below.Medical waste treatment optionsThe main treatment options are as follows: incineration, thermal treatment thermal disinfection with steam (autoclave) disinfection with microwaves chemical disinfection controlled medical landfill cell on sanitary landfill. All these options are considered as possible solutions that can guarantee the safe disposal of infectious and pathological medical waste. However, there are major differences between the economics of these options, as well as technical and environmental aspects.This article focuses on the treatment and disposal options for groups B, C and D (see Table 1). It does not deal with groups A and E as these groups should be treated/disposed of separately. Incineration and thermal treatmentVarious processes are available for the incineration or thermal treatment of medical waste. The most reliable and commonly used process is pyrolytic incineration - also known as controlled air incineration or double-chamber incineration. This process occurs in two stages.Stage one: pyrolytic chamber (primary or lower combustion chamber)Medical waste is fed into this chamber, which is operated with less than the stoichiometric amount of air required for combustion (oxygen-deficient). The low air-to-fuel ratio dries and facilitates volatilization of the waste and most of the residual carbon in the ash burns. At these conditions, the waste is thermally decomposed through a medium- temperature combustion process (800°-900°C), producing solid ash and gases. The pyrolytic chamber includes a fuel burner used to start the process.Stage two: secondary (or post-combustion) chamberIn the second stage, excess air is added to the volatile gases formed in the primary chamber. The aim is to complete the combustion and thereby minimize smoke and odours. The temperature in the secondary chamber is usually 900°-1200°C, depending on the moisture content/calorific value of the waste being incinerated.The capacity of controlled air incinerators can vary. Larger incinerators can handle 1-8 tonnes per day; usually they operate continuously and are equipped with flue gas cleaning technology. They may also be capable of fully automatic operation, including loading of waste, ash removal and internal movement of burning waste. Smaller incinerators, such as those commonly used in hospitals, are usually manually operated and are not equipped with flue gas cleaning equipment.Thermal disinfection with steamConventionally there are two types of equipment used for steam treatment - autoclaves and retorts. Other steam-based systems - sometimes referred to as advanced autoclaves - have been developed in recent years. A retort is similar to an autoclave except that a retort has no steam jacket. It is cheaper to construct but requires a higher steam temperature than an autoclave. A hospital autoclave sterilizes and dries medical waste to enable safe disposal. Click here to enlarge image Special bags containing medical waste are placed into a hermetic reaction chamber, which is cylindrical in shape. Here the waste is disinfected using steam at a temperature of around 110°-160°C, a pressure of 100-500 kPa and a retention time (cycle) of 30-90 minutes depending on the type and size of the equipment and the composition and humidity of the waste.1 The steam is normally generated by a small steam generator.Shredding of medical waste before treatment is recommended to allow better penetration of the material by the steam and to ensure destruction of pathogenic organisms. After shredding and thermal disinfection, the residue is inert and has the attributes of MSW. It can now be disposed of or treated as such. The disinfected waste should be analysed from time to time and measures taken to minimize the mercury content at source to ensure that the quality of the residue after disinfection is acceptable.Autoclave units are mainly used in larger hospitals. Plant throughput capacities vary considerably. A typical autoclave designed for medical waste treats about 100 kg per cycle (a cycle being about 1 hour). In contrast, autoclaves used in centralized treatment facilities can handle 3000 kg and more in one cycle.After disinfection, the treated waste (residue) is generally fed into a shredder or compactor prior to disposal in a sanitary landfill or, in the case of material with a high mercury content, to a secure, hazardous waste landfill. However, some landfill operators may refuse to accept residues from this disinfection process. Disinfection with microwavesThe concept of the microwave treatment of medical waste originated in the early 1980s in Germany. In a microwave treatment unit, a loading device transfers the waste into a shredder. The shredded waste is then humidified and transferred to an irradiation chamber equipped with a series of microwave generators. Microwaves are then used to heat the water within the waste to a temperature of 110°-120°C at a retention time of 30 minutes; the infectious components are destroyed by heat conduction.1 In order to increase the disinfection efficiency of the disinfection unit, the medical waste is turned continuously by means of a screw transporter. The microwave process disinfects medical waste via heat conduction. photo: san-i-pak Click here to enlarge image After irradiation, the disinfected waste is packed for transportation to a sanitary landfill, or if it has a high mercury content to a secure landfill. To maintain quality standards, regular bacteriological and virological tests of the disinfected waste need to be carried out and measures taken to decrease the mercury content at source.A typical microwave disinfection facility processes between 100 kg per cycle (a cycle being about 1 hour) to several hundred kilograms per cycle for larger hospitals. Plants used in centralized treatment facilities can handle 5000 kg and more in one cycle.Chemical disinfectionChemical disinfection is most efficient process for treating blood, urine, faeces and sewage. This method is also applicable for the treatment of infectious wastes containing pathogens. But to prevent environmental problems associated with the disposal of chemical residues, this process is only recommended for use if no other treatment or disposal facility is available.Chemicals such as aldehydes, chlorine compounds or phenolic compounds are added to the medical waste to kill or inactivate pathogens. Most of the commercial systems used shred the medical waste before disinfection. This is performed to increase the extent of contact between waste and disinfectant by increasing the surface area and eliminating any enclosed spaces. It also renders any body parts unrecognizable to avoid any adverse visual impact on disposal and reduces the volume of waste.1LandfillA landfill for handling medical waste must be situated and designed to meet set conditions to: prevent pollution of the soil, groundwater and/or surface water ensure efficient collection of leachate as and when required. Protection of soil, groundwater and surface water is achieved using a combination of geological barriers and geomembrane liners. Bottom liners should be used during the active phase of the landfill. Permanent top liners are also used after closure of the site.The geological barrier is provided by geological and hydrogeological conditions below and in the vicinity of a landfill site offering sufficient attenuation capacity to prevent a potential risk to soil and groundwater. In addition to such barriers, a leachate collection and sealing system should be added to ensure that leachate accumulation at the base of the landfill is kept to a minimum.The environmental impact of landfilling medical waste means that many countries do not allow untreated medical waste to be disposed of at landfills. At some sites, only residues from incineration, autoclave or microwave treatment can be landfilled. In general, the landfilling of medical waste is recommended only if other treatment facilities (incineration, autoclave, microwave) are not available.ConclusionThe decision about which medical waste treatment or disposal process to utilize is a complicated issue and goes far beyond cost considerations only. For example, it would be inappropriate if one option were selected or recommended solely based on environmental, social or technical points of view if its cost was more than the generators of the medical waste generators could afford. In contrast, it would be inappropriate to recommend a treatment option that did not take into consideration the local conditions and specifications of a particular site. An integrated approach is required.Medical waste management - in terms of defining waste types, collection, storage, labelling, transportation, treatment, disposal and relevant regulations - remains an unresolved issue in many countries worldwide, and particularly in developing countries. It is time to move forward from a strategic perspective, beginning with a clearer definition of the types of waste being handled.Ghassan Obid is a Senior Waste Management Expert at Fichtner Consulting & IT AG, Stuttgart, Germany.e-mail: Ghassan.Obid@fcit.fichtner.deNotes1. Prüss, A., Giroult, E. and Rushbrook P. Safe Management of Wastes from Healthcare Activities. World Health Organization, 1999.2. Development of a strategic and action plan for the collection and disposal of medical wastes from Greater Bandung, Indonesia. Study by Fichtner for the World Bank, November 2004.To comment on this article or to see related features from our archive, go to www.waste-management-world.com and click the ‘Forum’ tab.Evaluation of treatment optionsWhen assessing which option to pursue, the main criteria to be considered can be summarized as follows:2 regulatory requirements - current and forthcoming regulations governing each option economics criteria - the total investment costs and the total operating costs associated with each option technical criteria - covers aspects such as:- the ability of each option to treat different types of medical waste reliably in terms of mechanical destruction, microbial inactivation, emissions, regulatory acceptance and safety.- results to date, i.e. practical experience from using the technology and published data- requirement(s) for pre-treatment (shredding, grinding, etc.) and post-treatment- what is required from related staff. Some societies (particularly in developing countries) have experienced severe difficulties with operating and maintaining complex technologies and equipment due to problems such as the lack of appropriately skilled labour and difficulties in obtaining spare parts- availability of different designs with throughput rates appropriate for the types and amounts of medical waste to be treated. The design capacity should take into account future anticipated growth and variations in medical waste generation- flexibility of each option to handle different quantities of medical waste- reliability of equipment used in each option. High maintenance items include moving parts such as shredders, grinders and feed systems, and parts that are subjected to high thermal stresses.- other installation requirements, including the need for each treatment process to integrate with utilities such as electricity, gas and water. environmental criteria - again covers various aspects including:- environment impact - a complex factor to measure. It is important to consider emissions via all possible environmental media, i.e. air (workplace air, outside air), water (wastewater), noise, odour, etc.- quantity and quality of the residue(s) after treatment- infrastructure and space requirements for the treatment facility. Spatial planning is also an important political issue.- ability and efficiency of energy recovery from medical waste. In general, medical waste has a high calorific value of more than 14,000 kJ per kg or approximately 4 kWh/kg. public acceptance and education - it is important to assess the level of knowledge of the pros and cons of each option and the need to involve stakeholders in the selection process in order to gain support social-economic issues - including employment potential at the site private sector issues - the ability to accommodate private sector participation. The evaluation and comparison of different treatment options can be formally undertaken using a variety of methods. One such method is called utility value analysis. When using this approach, all those involved in making the final decision need to decide upon the exact criteria to be applied, yardsticks for measuring these criteria, hierarchy of objectives according to which the criteria are grouped, and criteria weightings.Please contact me for further information on using utility value analysis in this context and for the results of my analysis.