2.5 Types of waste and pollutants and tolerable concentration levels

Waste, mentioned above as the key source of geoenvironment contamination, can be classified into the following general categories:

• Mining waste.
• Radioactive waste.
• Non-point source discharge or diffused discharge waste, including pesticides, insecticides and fertilisers.
• Domestic sewage.
• Solid waste, including all solid, but also liquid waste not mentioned above.

Solid waste is a generic term, including all waste from municipal and industrial activities that can potentially contaminate the geoenvironment. Solid waste includes both hazardous (toxic) waste and non-hazardous waste. Toxic waste, which is mainly of interest here, include:

• Common industrial solvents.
• Wood treatment products.
• Chemical industry organic compounds and subproducts.
• Highly toxic compounds such as naphthalene, benzene, trichloroethylene (TCE), carbon tetrachloride (Freon, Halon), heavy metals (Hg, Pb) and various other compounds, such as arsenic, chromium, cyanides.

From a geoenvironmental engineering point of view, 4 major categories of soil waste are considered:

• Inorganic waste, suspended or dissolved in liquids, such as mercury, lead, chromium etc.
• Water-soluble organic waste or Aqueous Phase Liquids (APLs). Include solvents, pharmaceutical industry waste, pesticides, industrial waste etc.
• Non-water-soluble organic waste or Non-Aqueous Phase Liquids (NAPLs). Include oil paints, lubricants etc. Lighter than water NAPLs as petrol, kerosene, diesel are called Light NAPLs, while ones heavier than water are called Dense NAPLs. Trichloroethylene (TCE), one of the most common industrial solvents, is perhaps the most widespread organic waste traced in groundwater. Light NAPLs, which have a unit weight lower than water, are concentrated near the surface of the aquifer, while heavy NAPLs infiltrate and contaminate deeper aquifers.
• Viscose fluid and solid waste. Include oil refinery waste etc.

Various health organisations around the world have proposed different tolerable levels of contaminants concentration in the soil and groundwater, and different regulations apply in each country. Results of laboratory tests to measure pollutant concentration must be compared to reference, limit values (e.g., Table 2.1), which are related to the associated risk involved. In Australia, the following guidelines apply for soil contamination:

• Environmental Health Risk Assessment: Guidelines for assessing human health risks from environmental hazard. Department of Health and Ageing and EnHealth Council, Commonwealth of Australia, 2002.
• National Environment Protection (Assessment of Site Contamination) Measure 1999 – Schedule B (Guidelines).

Whereas the following guidelines refer to groundwater contamination:

• For drinking water: Australian and New Zealand guidelines for fresh and marine water quality.
• For aquatic ecosystems: NHMRC & NRMMC Australian drinking water guidelines 6.