Harmful Substances in Wastewater and Limits

The definition of harmful substances and their respective environmental limits and regulations are set by local authorities as well as national and international political organizations. Harmful substances can be categorized into chemical and physical pollutants and biological contaminants. Chemical and physical pollutants include heavy metals (chrome, zinc and nickel), organic particles (hair, food scraps and paper fibers), gasses and medicinal products, and hormones from pharmaceutical products. Biological contaminants include bacteria, viruses, protozoa and parasites. The following overview discusses harmful chemical and physical substances and their respective treatment options.

Biologically Degradable Pollutants

Organic pollutants originate in the food-and-beverage industries as well as in agriculture. In these areas, wastewater technology needs to treat dissolved sugar, proteins and fats, and the residue of animal feces.

Another challenge is when organic wastewater contents such as ammonium, nitrate and dissolved carbon compounds (such as isopropyl alcohol) need to be treated. Water-soluble nitrogen and sulfur compounds, sulphates and chlorides, as they typically occur in landfill leachate (among others), can also be degraded biologically.

In the paper industry, along with fiber residue, typical pollutants are de-inking chemicals, bleaching agents, process chemicals and additives. Difficult to degrade substances and tensides in the cosmetics industry are also challenging.

Chemically and Physically Degradable Pollutants

There is a wide spectrum of applications to chemically and physically degradablepollutants. One application is the separation of fine particles or driblets from fluids using micro-bubbles to separate oils, fats, and finely suspended solids from wastewaters. This process is typically used in the cosmetic industry, where tensides, colorants, oils and emulsions are among common pollutants. The separation of solids (via ultra-filtration, micro-filtration) or of ions (nano-filtration, reverse osmosis) is another important task in wastewater treatment.

Other industry-specific tasks are: