Analysis and Treatment of Waste

　　“Waste” refers to waste generated by health care institutions in the course of prevention, health care, and other related activities that poses direct or indirect infectious, toxic, or other harmful risks. The total volume of waste produced by hospitals is typically calculated based on the number of inpatients and the total outpatient volume. According to domestic and international experience over the past several decades, the waste generation per inpatient bed ranges from 0.5 to 1.0 kg per bed, while the outpatient department generates approximately 1 kg per 20 to 30 patients per day [1]. Waste management is an essential component of both current and future hospital operations and a critical guarantee for the sustainable economic development of hospitals. At present, hospital environmental protection facilities lag behind the pace of institutional development; some waste treatment processes have yet to meet the requirements for harmless disposal, primarily due to inadequate equipment, aging infrastructure, leaks in the wastewater collection network, and insufficient wastewater discharge volumes. Given the unique characteristics of various types of waste—such as infectious, pathological, chemical, sharp-object-related, and toxic waste—improper handling can cause significant harm to the environment and human health.
　　Waste primarily includes solid waste such as surgical and dressing residues, disposable syringes, infusion sets, biological culture materials, animal experiment leftovers, laboratory waste, expired medications, plaster casts, glassware, as well as human organs removed during surgery, tree stumps, wound dressings, patient excreta, vomitus, and various household items used by patients with infectious diseases. In today’s society, with the continuous advancement of technology, the volume of waste has grown at an alarming rate. Data show that our hospital generates an average of 1,000 grams of waste per bed per day; in medium-sized cities, daily waste generation is approximately 40 to 70 tons, amounting to as much as 9,600 tons annually.
　　The most obvious hazard of medical waste is its infectiousness. China’s health authorities have stringent regulations governing the “burial” of such waste. However, it is alarming that a substantial amount of this waste is neither properly disinfected nor adequately treated, and is instead directly released into the environment. For example, single-use medical devices are sometimes reused, and disposable syringes are crudely washed and repurposed as other plastic products. Such improperly managed medical waste can contaminate our drinking water, everyday consumer goods, and even the air we breathe.
　　The dangers of waste extend beyond its secondary use. In fact, even when properly managed, improper handling can turn waste into a potential health hazard. Currently, Chinese regulations mandate that medical waste be incinerated; however, many facilities fail to comply with these requirements. A significant number of small hospitals operate small-scale incinerators, which often encounter numerous operational problems during the combustion process. As a result, waste is not fully burned, leading to the formation of toxic dioxins and posing serious risks to human health.
　　First, analyze the problems and hazards in waste management.
　　1. Existing problems
　　Due to limitations in waste treatment methods, waste can only be sorted through recycling (plastics and glass) and incineration. Liquid waste, which cannot be burned due to its recyclability or reuse value—such as disinfectants and other liquid formulations—when discharged into wastewater, leads to severe water pollution. Genotoxic and chemically hazardous solid waste is often co-mixed and landfilled, resulting in soil contamination.
　　Currently, Nanjing has established two waste treatment centers. All entities are required to implement unified collection and centralized storage, and the waste is transported in a closed manner in accordance with national regulations on the transport of hazardous materials before being incinerated. However, several issues remain in the implementation process. For instance, during incineration, highly toxic substances such as carbon monoxide, sulfur dioxide, and particulate matter are generated; although these emissions must meet national standards, further investigation is needed into whether small hospitals and clinics are subject to centralized treatment.
　　Although waste is treated by incineration, only 11.23% is actually burned; the remaining 88.50% is recycled. For example, 4.46% of the waste consists of single-use plastics that are approved for recycling by the sanitary authorities and processed at designated plastic-recycling facilities. However, a substantial quantity of infusion bottles is not being recycled. Although this type of waste is not contaminated with pathogens, it does contain certain chemical components that may have adverse effects on human health. Consequently, how such waste should be recycled and properly managed—particularly in terms of preventing its proliferation and potential new health risks—has become a matter of widespread public concern. Moreover, the lack of clear regulatory guidance and differing opinions among the relevant supervisory authorities further exacerbates public apprehension.
　　2. The Harm of Waste
　　(1) Impact on the soil environment: The storage or landfilling of waste not only occupies land but also contaminates the soil, with solid waste reportedly covering an area of approximately 666 million square meters. The discharge and accumulation of large quantities of waste damage landforms, vegetation, and natural landscapes. When waste is simply piled up or when appropriate leachate-proofing measures are lacking, harmful constituents in the waste can easily leach into the soil, killing soil microorganisms, depleting soil fertility, and disrupting the plant growth environment.
　　(2) Impacts on the aquatic and atmospheric environments: If waste treatment or landfill operations are not properly sealed against leaching, solid waste may enter surrounding surface waters or percolate into soils that receive natural precipitation and surface runoff; wastewater discharge can lead to water pollution; and direct discharge of waste into rivers, lakes, or the ocean will also cause water contamination. Waste incineration, particularly the combustion of chlorine-containing wastes, if not properly managed, can generate substantial amounts of dioxins—known carcinogens—according to cancer research centers. Due to their chemical stability, dioxins have a half-life of typically 5 to 10 years, resulting in severe pollution of the atmosphere, soil, rivers, and lakes [3]. According to reports [4], approximately two-thirds of U.S. municipal solid-waste incinerators contribute to air pollution because they lack air-purification equipment, and 42% of U.S. air pollution originates from solid-waste management activities. Given that plastic products constitute a larger proportion of waste than household refuse, their incineration produces high concentrations of dioxins. Therefore, special attention must be paid to minimizing dioxin formation during waste disposal. In addition, certain types of waste, such as syringes and infusion sets, should be centrally collected and disposed of through authorized channels rather than being discarded directly into garbage, as indiscriminate disposal can adversely affect the living environment.
　　Two, Waste
　　1. Sanitary Landfill
　　(1) Principles
　　Sanitary landfill is a method of waste disposal that relies on the long-term action of decomposing microorganisms to break down waste into harmless substances, which are then buried underground. Without impermeable barriers, various toxic substances, pathogens, and radioactive materials can leach into the soil, where they may enter the human body through the food chain and pose serious health risks. Therefore, sanitary landfills must be sited in accordance with scientific principles and constructed with impermeable liners made of materials such as clay and high-density polyethylene. In addition, landfill gas collection and venting systems must be installed. Consequently, landfill treatment requires extreme caution, and waste must undergo rigorous pre-treatment in compliance with relevant regulations.
　　(2) Influencing parameters
　　The selection and application of landfill disposal methods shall be based on the characteristics of the waste, taking into account site-specific geological conditions as well as local soil and climatic factors, and employing appropriate civil engineering techniques to determine the appropriate scale of on-site construction.
　　(3) Pros and Cons
　　The advantages of landfilling lie in its relative simplicity and lower capital investment, enabling the treatment of large volumes of waste. The main drawbacks include the need for extensive land use prior to site remediation, the generation of harmful gases such as methane, ammonia, hydrogen sulfide, nitrogen, and carbon monoxide, as well as the release of oxygen and hydrogen and volatile organic compounds, and the requirement for long-term monitoring of soil and groundwater.
　　2. High-Temperature Incineration
　　(1) Technical Features
　　Waste is primarily composed of organic hydrocarbons, with a high content of combustible components and a high calorific value, making incineration a fully viable treatment option. Incineration is a chemical process involving deep oxidation; under the action of a high-temperature flame, the waste undergoes three stages—drying, ignition, and combustion—ultimately yielding residual ash and gaseous byproducts. During incineration, pathogens and hazardous substances contained in the waste are effectively destroyed. Incineration technology is suitable for various types of infectious waste. However, it requires stable high temperatures within the incinerator, adequate oxygen mixing, sufficient gas residence time, and other necessary operating conditions, as well as subsequent treatment of flue gases and residues to ensure their safe and harmless disposal.
　　(2) Influencing parameters
　　The selection of incineration equipment must ensure appropriate turbulence and mixing, while maintaining the waste at its current moisture content; furthermore, furnace load, temperature, and residence time are all critical incineration parameters that must be carefully controlled during operation, maintenance, and repair.
　　(3) Pros and Cons
　　The main advantages of incineration technology are significant reductions in volume and weight, as well as the effective destruction of waste; it is suitable for a wide range of waste types and large-scale applications; it operates smoothly and provides excellent disinfection and decontamination; and its waste heat can potentially be recovered and utilized. However, the technology is relatively mature, with drawbacks including high costs, severe air pollution, and the easy formation of toxic substances such as dioxins, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls, as well as harmful gases like hydrogen chloride, hydrogen fluoride, and sulfur dioxide, necessitating exhaust gas purification systems. Moreover, the resulting slag and fly ash are hazardous.
　　3. Steam Pressure Method
　　(1) Technical Principles and Characteristics
　　The principle of the pressurized steam method is to subject sorted and shredded waste to treatment at 100 kPa and 121°C for at least 20 minutes, allowing the pressurized steam to penetrate deep into the material and denature microbial proteins through coagulation and precipitation, thereby inactivating microorganisms. The treated waste is then disposed of in a sanitary landfill or incinerated. This method is also suitable for disinfecting contaminated workwear, syringes, dressings, and microbial cultures; however, it is not appropriate for handling pathological wastes such as human tissues and animal carcasses, and its efficiency in treating chemical wastes is relatively low.
　　(2) Influencing parameters
　　The primary technical parameters of the pressurized steam process are temperature, steam quality, and processing time. The particle size of the waste material affects permeability, while the duration of the treatment cycle influences the thoroughness of the process. Removal of air from the vessel does not affect the temperature.
　　(3) Pros and Cons
　　Pressure steam sterilization boasts several advantages, including low capital investment, low operating costs, ease of monitoring, minimal residual risk, excellent disinfection efficacy, and a broad range of applications. Its main drawbacks are that the equipment’s size and appearance remain largely unchanged; it may emit air pollutants and produce odors; and it is incapable of treating substances such as formaldehyde, phenol, and mercury.
　　4. Chemical Disinfection Methods
　　(1) Technical Features
　　Chemical disinfection involves mixing waste at a specified concentration with a disinfectant of appropriate concentration—such as sodium hypochlorite, peracetic acid, glutaraldehyde, or ozone—and ensuring thorough contact between the waste and the disinfectant in terms of both contact area and contact time. During the disinfection process, organic matter is degraded and microorganisms are killed. Maximizing the contact between the disinfectant and the waste is a prerequisite for effective disinfection. The use of rotary shredding equipment can enhance the degree of fragmentation, thereby facilitating the penetration of the disinfectant. Chemical disinfection is suitable for liquid wastes and pathological waste and has recently been increasingly applied to the treatment of wastes that cannot be disinfected by heat or moist methods.
　　(2) Influencing parameters
　　The factors that determine the efficacy of chemical disinfection are the concentration of the disinfectant and the temperature at which it is applied. Depending on the nature of the waste, it is also important to select a disinfectant with an appropriate pH, taking into account the mixing time between the waste and the disinfectant as well as the recirculation of the fluid.
　　(3) Pros and Cons
　　Chemical disinfection is characterized by simple and convenient process equipment operation, excellent deodorization performance, rapid disinfection, and low initial capital investment, resulting in low operating costs. For dry treatment, the waste reduction rate is high, and no solid waste, wastewater, or gaseous emissions are generated. However, dry waste treatment requires a more sophisticated crushing system and advanced pH monitoring (with a high degree of automation) for proper operation. In contrast, wet waste treatment generates sludge and liquid waste, and most disinfectants used in such processes are harmful to human health. This method is not suitable for treating chemical waste, radioactive waste, or volatile and semi-volatile organic compounds.
　　5. Electromagnetic Wave Method
　　(1) Technical Principles
　　Electromagnetic-wave disinfection methods include microwave and radio-wave techniques. The microwave method employs high-frequency electromagnetic waves at 2,450 MHz, whereas the radio-wave method uses low-frequency waves at 10 MHz; the latter exhibits stronger penetration than microwaves. These electromagnetic methods are based on the absorption characteristics of water, fats, and proteins, leveraging the selective energy-absorption properties of microbial cells. When microorganisms are exposed to a high-frequency oscillating electromagnetic field, the vibrational energy of liquid molecules within the cells increases rapidly due to the external electric field, leading to a rise in intracellular temperature and ultimately causing cell death, thereby eliminating pathogens in waste. After electromagnetic treatment, such waste can be safely disposed of in sanitary landfills. Electromagnetic-wave technologies have been successfully implemented in the United States, Australia, Germany, and the Philippines.
　　(2) Influencing parameters
　　For both microwave and radio wave treatments, the key factors determining the disinfection efficacy are the output power and the actual field strength. Moreover, depending on the characteristics of the waste, microwave treatment exhibits a pronounced effect on wastewater content, while exposure time and the degree of mixing within the waste also exert a certain influence.
　　(3) Pros and Cons
　　The advantages of the electromagnetic wave method include a significant reduction in volume and minimal impact from waste degradation; the system is fully enclosed, resulting in very low environmental pollution; and it is fully automated and easy to operate. The disadvantages are relatively high construction and operational costs; poor odor control, with potential odor emissions; and unsuitability for handling blood and hazardous chemicals.
　　6. Dry-heat crushing method
　　(1) Technical Principles
　　Dry heat refers to the process of placing items in dry-heat sterilizers, tunnel-type ovens, and similar equipment, where dry hot air is used to kill microorganisms. Currently, far-infrared dry-heat disinfection equipment is predominantly employed, along with sealed waste-incineration furnaces that utilize high-temperature thermal treatment for certain types of special waste. During dry-heat processing, items must be properly loaded and not placed too close together to ensure effective and uniform treatment.
　　(2) Influencing parameters
　　The primary sterilizing factor in dry-heat treatment is high temperature, which must be maintained for a sufficient duration to meet the required standards; the characteristics of the waste must also comply with the requirements for dry-heat treatment.
　　(3) Pros and Cons
　　The main advantages of dry thermal treatment are its reliable performance, low construction and operating costs, and the fact that the treated waste can be disposed of in landfills or subjected to comprehensive utilization. The process does not involve the use of disinfectants. Its disadvantages include the need for pre-treatment such as crushing, slow heat transfer, potential emissions of air pollutants, and a tendency to generate odors.