3 Best practices for incineration - WHO

1 12 3 best practices for incineration This section discusses best practices for incineration , which can lead to substantial reductions in the formation, emission and exposure to toxic substances from waste incineration . Waste reduction Waste reduction reduces the volume and toxicity of materials for incineration (or other treatment option), thus decreasing incinerator use, emissions and the resulting health and environmental risks. For example, incineration might be reserved for only the most dangerous types of waste, , contaminated sharps. Waste reduction can substantially lower demands for incineration and provide other important benefits, , greater environmental protection, enhanced occupational safety and health, cost reductions, reduced liability, regulatory compliance, and improved community relations (HCWH 2001).

2 As mentioned, extensive reviews of waste reduction have been provided elsewhere (HCWH 2001; 2002; WHO 1999). General approaches include source reduction, material elimination, recycling, product substitution; technology or process change, use of good operating practices , and preferential purchasing. Hospitals and other facilities have many opportunities to minimize waste, including: Segregating wastes. This requires clearly marked and appropriate containers, staff training to separate various wastes (health-care waste, hazardous waste such as mercury, low-level radioactive waste, and regular trash), minor maintenance infrastructure (containers, suitable space) and management support.

3 Studies in Nigeria and Benin show that health-care waste is either not segregated or insufficiently segregated (Adama 2003). The same study shows that policies and action plans are not sufficient or not comprehensive enough to address this problem. Reducing unnecessary injections (as much as 70% of all injections may be unnecessary) (Gumodoka et al., 1996). Recovering silver from photographic chemicals. Eliminating mercury products and mercury-containing instruments. Buying PVC-free plastic products. Treatments to remove and concentrate waste, , filters and traps to remove mercury from wastewater. Effective waste reduction programs require commitment of top management and effective communication among hospital staff.

4 Physicians, other medical staff and managers must be made aware of waste generation and associated hazards. Source reduction requires involvement of purchasing staff and periodic reassessment. These programs require staff and moderate infrastructure support, planning and organization, assessment, feasibility analysis, implementation, training, and periodic evaluation. A waste audit will generally be helpful. Design Proper design and operation of incinerators should achieve desired temperatures, residence times, and other conditions necessary to destroy pathogens, minimize emissions, avoid clinker formation and slagging of the ash (in the primary chamber), avoid refractory damage destruction, and minimize fuel consumption.

5 Good combustion practice (GCP) elements also should be followed to control dioxin and furan emissions (Brna and Kilgroe 1989). Table 2 provides recommendations for small-scale intermittent incinerators. 13It appears that the temperature, residence time and other recommendations in Table 2 are rarely achieved by small-scale incinerators. Additionally, as mentioned earlier, few small-scale units utilize air pollution control equipment. Siting The location of an incinerator can significantly affect dispersion of the plume from the chimney, which in turn affects ambient concentrations, deposition and exposures to workers and the community.

6 In addition to addressing the physical factors affecting dispersion, siting must also address issues of permissions/ownership, access, convenience, etc. best practices siting has the goal of finding a location for the incinerator that minimizes potential risks to public health and the environment (EPA 1997). This can be achieved by: Minimizing ambient air concentrations and deposition of pollutants to soils, foods, and other surfaces, , o Open fields or hilltops without trees or tall vegetation are preferable. Siting within forested areas is not advisable as dispersion will be significantly impaired. o Valleys, areas near ridges, wooded areas should be avoided as these tend to channel winds and/or plumes tend to impinge on elevated surfaces or downwash under some conditions.

7 Minimizing the number of people potentially exposed, , o Areas near the incinerator should not be populated, , containing housing, athletic fields, markets or other areas where people congregate. o Areas near the incinerators should not be used for agriculture purposes, , leafy crops, grasses or grains for animals. Appropriate sizes for buffer surrounding incinerators are based on dispersion modeling (Section ). For typical small-scale units, especially if nighttime operation may occur, a 500 to 750 m buffer surrounding the facility is advisable to achieve dilution ratios above 1000. During the day, a 250 m buffer should obtain the same dilution ratio.

8 These distances are based on ideal conditions, , relatively flat and unobstructed terrain. 14 Table 2 Recommendations of key design/operating parameters for small-scale intermittent incinerators. Derived in part from EPA (1990), UNDP (2003), and De Montfort literature. Type Parameter Recommendation Capacity Destruction rate, safety boxes capacity District/subdistricts in Taylor (2003) that regularly used incinerators destroyed an average of 58 safety boxes per month, about 14 per week, equivalent to ~12 kg/week. Remote areas may only generate 1 kg per month.

9 Proper sizing is important. Ideally, unit should burn for long periods (~4 hrs) to save fuel. (De Montfort units are not suitable for short sharp burns without a warm up period, though this appears to be common practice). Temperatures Primary chamber 540 to 980 C Secondary chamber 980 to 1200 C (EPA 1990 recommendations) >850/1100* C (S. African and EU standards) >1000/1100* C (Indian and Thai standards) * more than 1% chlorinated organic matter in waste Gas entering air pollution control devices, if any <230 C Residence times Gas (secondary chamber) >1 s Air flows Total combustion air 140 200% excess Supply and distribution of air in the incinerator Adequate Mixing of combustion gas and air in all zones Good mixing Particulate matter entrainment into flue gas leaving the incinerator Minimize by keeping moderate air velocity to avoid fluidization of the waste, especially if high (>2%) ash waste is burned.

10 Controls & Monitoring Temperature and many other parameters Continuous for some, periodic for others Waste Waste destruction efficiency >90% by weight Uniform waste feed Uniform waste feed, and avoid overloading the incinerator Minimizing emissions of HCl, D/F, metals, other pollutants Avoid plastics that contain chlorine (polyvinyl chloride products, , blood bags, IV bags, IV tubes, etc. Avoid heavy metals, , mercury from broken thermometers etc. Load/charge only when incinerator operating conditions are appropriate Pre-heat incinerator and ensure temperatures above 800 C. Avoid overheating. Enclosure Roof A roof may be fitted to protect the operator from rain, but only minimum walls. Chimney Height At least 4 5 m high, needed for both adequate dispersion plus draft for proper air flow Pollution control equipment Installing air pollution control devices (APCD) Most frequently used controls include packed bed, venturi or other wet scrubbers, fabric filter typically used with a dry injection system, and infrequently electrostatic precipitator (ESP).)