Proper Treatment and Disposal

Waste can be treated and disposed of through five major pathways, according to the waste management hierarchy: reduction, reuse, recycling and composting, energy recovery, and landfill, each of which has its implementation challenges.

Several types of plastic, such as thermoset, cannot be recycled. Thermoset, unlike conventional thermoplastic, is highly popular because of its stronger dimensional stability and higher chemical resistance, and is used in the automotive industry, adhesives, coatings, shore structures, clean energy production, solar cells, and electronic packaging utensils. Unfortunately, it cannot be dissolved or melted (Yue et al., 2019).

Disposal into a landfill is the most common treatment of waste from municipal, construction and demolition, and industrial activities, but landfills are a source of marine plastic debris, not a solution. Research on potential microplastic sources demonstrates they can enter the environment through leachate leakage. The geomembrane component of a landfill composite liner, designed to prevent groundwater pollution, can leak even if highly controlled (Foose et al, 2001).

Although leachate treatment is more complex than municipal wastewater treatment because it comprises biological, physical, chemical, and membrane treatment to eliminate chemical contamination, the process cannot thermally, chemically, and biologically remove microplastic. It only changes microplastic distribution, where high-density microplastic accumulates at the bottom of the basin and then becomes sludge and finally effluent. Microplastic can also be found in the landfill itself, attracted by its fine soil-like fraction, where microplastic tends to accumulate and is eventually distributed to a marine environment by wind or surface run-off.

Microplastic can be discharged from landfills through ventilation in aerated bioreactors or closed landfills. Yet, a huge amount of plastic is still disposed into landfills, contributing 21%–42% of global plastic waste production.

The Philippines endorsed the implementation of sanitary landfills instead of open and controlled dumps through Republic Act No. 9003 on Ecological Solid Waste Management Program. Section 37 states that open and controlled dumps in local government units (LGUs) must be closed in three to five years after the issuance of the regulation. A sanitary landfill is defined as a site to dispose waste, and is designed, constructed, operated, and maintained under engineering controls to reduce potential environmental impacts from the development and operation of the facility. Section 41 states that to establish a sanitary landfill, liners and a leachate collection and treatment system must be provided. Liners reduce or prevent groundwater contamination, while a leachate collection and treatment system collects leachate for storage and eventual treatment and discharge.

Under the Implementing Rules and Regulations of Republic Act 9003, a sanitary landfill must have at least 6 inches of cover every day. Initially, the daily cover is applied to prevent waste from long-term contact with the environment. For a landfill area that will not be used for at least 180 days, an additional 6-inch-thick interim soil cover must be applied over the existing daily cover. Republic Act 9003 has had a significant impact, with illegal dumpsites decreasing from 806 to 353 in 10 years. The number of sanitary landfills has grown, from 33 sanitary landfills serving 78 LGUs in 2010 to 165 serving 353 LGUs in 2018 (Environmental Management Bureau, 2018). The combined liners, daily cover, and leachate collection and treatment in sanitary landfills can help reduce microplastic pollution.

Bukit Tagar Sanitary Landfill in Malaysia, an advanced landfill treatment, is a government privatisation project with a capacity up to 120 million tonnes of waste. Although all landfills potentially leak, the design of Bukit Tagar Sanitary Landfill applies the highest level of sanitary landfill standards from the United States Environmental Protection Agency through a multi-layer base liner to block leachate infiltration to the soil. Collected leachate goes to a treatment plant mainly using a biological reaction process combined with chemical dosing. After being purified in the treatment plant, the leachate is further polished by reed beds technology to achieve zero residue.

Incineration is the second most common option for waste treatment and disposal after landfills. Combustible waste, such as municipal solid waste, hazardous waste, clinical waste, and industrial waste, is suitable for treatment by incineration (Williams, 2004). Combustion control is taken into account to prevent incomplete combustion, which can result in dioxins and furans. A well-designed incinerator enables controlled air flow, leading to the generation of high temperatures and a clean burn. The recommended temperature for the incinerator's primary chamber is 540–980 degrees Celsius, according to EPA 1990, and 980–1,200 degrees Celsius for the second chamber (WHO, n.d.). Production of dioxin in large-scale incineration can be minimised through fast cooling combustion, where the time spent in 200–450 degree Celsius is shortened, leading to the generation of cleaner combustion (Environment Australia,1999; Soares, 2015).

Incineration technology has been a concern of the Japan government since the enactment of the Act on Emergency Measures Concerning the Development of Living Environment Facilities in 1963 (Ministry of Environment of Japan, 2014). Japan has incineration plants spread across the country which apply strict policies to reduce pollution, and has determined the conventional stoker furnace is the most reliable technology. As a result, stoker furnace technology is used in 70% of incineration plants.

The main difference between a stoker furnace and a conventional one is that the former allows higher combustion quality derived from a lower combustion air ratio, improvement of combustion gas and air mixing, improvement of oxygen-enriched combustion and combustion quality, and generation of evenly burnt materials with an infusion of high temperature air. The secondary chamber of the latest stoker furnace technology reaches 1,000 degrees Celsius to ensure a complete combustion reaction (Ministry of Environment of Japan, 2012). Replacing a multiple-heart furnace with a stoker furnace has had a positive impact in the city of Kyoto, including 50% ash reduction, 77% reduction of energy consumption, and 18% reduction of operating costs (Ito, 1991).

Waste treatment and disposal are highly dependent on cost. The United Nations Environment Programme notes that in waste management, the financial cost is divided into investment and operation costs. Investment cost is usually prioritised as it is related to the modernisation of waste management infrastructure, such as equipment and technology.

Operation cost is frequently overlooked, yet it accounts for up to 60%–70% of the total cost of waste management, covering labour, fuel, energy, maintenance and repair, emission control and monitoring, income collection, public communication, and management and administration. While investment cost can be easily estimated, operation cost is difficult to estimate because of the various aggregation methods used to calculate budgets. For example, allocation of operation cost in cities sometimes overlaps with other public utilities because waste management is not regarded as a common activity. This leads to cities not allocating for operation cost. Unavailable operation data is another reason why determining operation cost is complicated and challenging.