(1) Types of pollutants
Pollutants common in HWLFs include slag, fly ash, sludge, solidified fly ash,
electroplating sludge, inorganic cyanide waste, non-ferrous metal waste,
chromium-containing waste, zinc-containing waste, copper-containing waste,
arsenic-containing waste, lead-containing waste, mercury-containing waste,
strontium-containing waste, nickel-containing waste, cadmium-containing waste,
fluoride, cyanide, paint waste, surface treatment waste, incineration residue,
incineration fly ash, sewage treatment sludge, industrial water treatment sludge,
solid waste from automotive industry, and cured dye block. They vary in characteristics and hazards, as well as in migration and transformation in groundwater.
The results of investigation and analysis showed that the main pollutant types are
slag and typically, fly ash (solidified fly ash) and sludge, and the dominant hazardous components are heavy metals. Before final safe landfill, hazardous waste
must be pretreated and the products evaluated and proved to reach the acceptance
criteria for typical hazardous wastes (Zhang 2014).
(2) Components and contents
The hazardous components of typical HWLFs leachate fail to meet the acceptance
criteria. Regardless of the level of development in different regions, hazardous
wastes have similar components of heavy metals. Among them, the hazardous
components beyond the acceptance limits mainly include mercury, lead, zinc and
chromium. In addition, the hazardous components of typical HWLFs leachate
generally exceed the Grade III limits of groundwater quality standards (Liu 2017).
(3) Landfill security techniques
Techniques for the disposal of hazardous wastes are divided into pretreatment and
final disposal. Pretreatment is to treat hazardous wastes by physical, chemical or
biological methods before final disposal, so that their physical, chemical, biological
and other characteristics are changed to achieve minimum toxicity, volume and
landfill occupation (Geng 2017).
In specific, the physical methods of pretreatment mainly include curing/
stabilization and phase separation, while oxidation reduction and acid-base neutralization are commonly used chemical methods. Chemical pretreatment changes
the harmful components of waste through chemical reactions towards safety or
transforms waste into a form suitable for further disposal. It is mainly applied to
inorganic waste, such as acid, alkali, heavy metal waste liquid, cyanide waste
liquid, cyanide and emulsified oil. Biological pretreatment means
biodegradation-based decomposition of organic matter in hazardous waste, and
mainly applies to organic waste or wastewater. The prevailing methods include
anaerobic treatment, aerobic treatment and facultative anaerobic treatment, which
can be achieved through activated sludge process, aeration pond, anaerobic
digestion, composting treatment, biological filter, and stabilization pond.
Safe landfills provide the final disposal of hazardous waste. During landfill
operation, waste may physico-chemically react with rainwater or other substances
3.1 Indicators of Pollution Source Intensity Evaluation
35
Pollutants common in HWLFs include slag, fly ash, sludge, solidified fly ash,
electroplating sludge, inorganic cyanide waste, non-ferrous metal waste,
chromium-containing waste, zinc-containing waste, copper-containing waste,
arsenic-containing waste, lead-containing waste, mercury-containing waste,
strontium-containing waste, nickel-containing waste, cadmium-containing waste,
fluoride, cyanide, paint waste, surface treatment waste, incineration residue,
incineration fly ash, sewage treatment sludge, industrial water treatment sludge,
solid waste from automotive industry, and cured dye block. They vary in characteristics and hazards, as well as in migration and transformation in groundwater.
The results of investigation and analysis showed that the main pollutant types are
slag and typically, fly ash (solidified fly ash) and sludge, and the dominant hazardous components are heavy metals. Before final safe landfill, hazardous waste
must be pretreated and the products evaluated and proved to reach the acceptance
criteria for typical hazardous wastes (Zhang 2014).
(2) Components and contents
The hazardous components of typical HWLFs leachate fail to meet the acceptance
criteria. Regardless of the level of development in different regions, hazardous
wastes have similar components of heavy metals. Among them, the hazardous
components beyond the acceptance limits mainly include mercury, lead, zinc and
chromium. In addition, the hazardous components of typical HWLFs leachate
generally exceed the Grade III limits of groundwater quality standards (Liu 2017).
(3) Landfill security techniques
Techniques for the disposal of hazardous wastes are divided into pretreatment and
final disposal. Pretreatment is to treat hazardous wastes by physical, chemical or
biological methods before final disposal, so that their physical, chemical, biological
and other characteristics are changed to achieve minimum toxicity, volume and
landfill occupation (Geng 2017).
In specific, the physical methods of pretreatment mainly include curing/
stabilization and phase separation, while oxidation reduction and acid-base neutralization are commonly used chemical methods. Chemical pretreatment changes
the harmful components of waste through chemical reactions towards safety or
transforms waste into a form suitable for further disposal. It is mainly applied to
inorganic waste, such as acid, alkali, heavy metal waste liquid, cyanide waste
liquid, cyanide and emulsified oil. Biological pretreatment means
biodegradation-based decomposition of organic matter in hazardous waste, and
mainly applies to organic waste or wastewater. The prevailing methods include
anaerobic treatment, aerobic treatment and facultative anaerobic treatment, which
can be achieved through activated sludge process, aeration pond, anaerobic
digestion, composting treatment, biological filter, and stabilization pond.
Safe landfills provide the final disposal of hazardous waste. During landfill
operation, waste may physico-chemically react with rainwater or other substances
3.1 Indicators of Pollution Source Intensity Evaluation
35