Glossary

General Terms

Bacteria

Single-celled microorganisms that lack chlorophyll. Some bacteria are capable of causing human, animal or plant diseases; others are essential for the decomposition of organic matter in soils, in secondary wastewater treatment, and in digestive processes in animals.

Essential element

An element that is required by all organisms in order to survive and reproduceA

Heavy metal

Metallic elements whose densities are equal to or greater than 5.0 g/cm3 including, but not limited to chromium, lead, zinc, copper, cadmium, mercury, nickel, silver, and iron. Some heavy metals are required in trace concentrations for all animal and plant life. These include manganese, iron, copper, zinc, and molybdenum. Others like cadmium, mercury, and lead can be toxic to living organisms. Still others have no known effects on living organisms.

Macronutrient

An essential element needed in large amounts by a plant or animal in order to survive and reproduce. Plant macronutrients include nitrogen, phosphorus, potassium, sulfur, calcium, magnesium, carbon, hydrogen and oxygen.

Microconstituent/trace organic compounds

Any orgnanic compound (usually from pharmaceuticals, personal care products, and other chemicals), detected in biosolids in extremely small amounts, usually several parts per million (mg/kg, or approximately 1 drop of water in a 10 gallon fish tank) or less.

Micronutrient

An essential element needed in very small amounts by a plant or animal in order to survive and reproduce. Plant micronutrients include iron, boron, manganese, zinc, copper, chloride, cobalt, and molybdenum. Soils that have had a lot of agricultural use or synthetic fertilizer use often lack micronutrients.

Microorganism

A microscopic organism, especially a bacterium, virus, or fungus.

Nutrients

An essential element needed in certain amounts by plants or animals in order to survive and reproduce.

Pathogen

Any microorganism that has the potential to cause disease, including pathogenic bacteria, viruses, helminths, and protozoans. These may include certain fungi.

Pollution

Results when contaminants in human, animal, vegetable, mineral, chemical or thermal waste or discharges reach water, making it less desirable for domestic, recreation, industry, or wildlife uses.

Priority pollutants

A group of chemicals specifically listed in the Code of Federal Regulations (40 CFR 423, Appendix A; 40 CFR 122 Appendix D) given priority for regulatory control by the Environmental
Protection Agency.

Trace metal

Any metallic element found in biosolids in extremely small amounts. Trace metals are micronutrients for plants, although not all micronutrients are metals.

Virus

The smallest of the microorganisms, often capable of causing disease, these are obligate parasites composed of a nucleic acid (RNA or DNA) core and a protein coat. They cannot grow or reproduce outside a host organism.

Volatile organic compounds (VOC’s)

VOC’s are emitted as gases from certain solids or liquids found in a wide array of products, including fuels, solvents, and degreasers; paints, paint strippers, and wood preservatives; household products, cleansers and disinfectants.

Treatment process

Aerobic digestion

The decomposition of organic matter (plant and animal material) by microorganisms with the presence of oxygen.

Anaerobic digestion

The decomposition of organic matter (plant and animal material) by microorganisms, without the presence of oxygen. Anaerobic digestion of wastewater solids takes place in tanks where the solids are decomposed by anaerobic bacteria and converted to biogas and a semi-solid biosolids product. Anaerobic digestion also typically reduces viruses and pathogens by 90 percent or more.

Composting

Is the natural biological decomposition of organic material in the presence of air to form a stabilized, humus-like material.

Dewatering

Any of several processes used to remove water from biosolids in order to reduce its volume and weight prior to recycling. These processes may include evaporation, passage through a belt filter press that squeeze water out of biosolids, or centrifuging which drives water out by spinning, much as water is driven out of clothes during the “spin” cycle of a clothes washing machine.

Digestion

Digestion of solids takes place in heated tanks where microorganisms break down material.

Disinfection

The use of chemicals to kill any disease causing organisms in the polished wastewater. UV light can also be used.

Incineration

Involves combustion of the organic matter in sewage sludge, producing a residual inert ash that generally must be landfilled.

Lagoon

Is a shallow pond in which algae, aerobic and anaerobic bacterial purify wastewater.

Mesophilic digestion

Biological degradation process where the temperature in the digester is maintained within the range of 85-100oF (30-38oC).

Ozonation

Is a disinfection process where ozone is generated and added to wastewater effluent to kill pathogenic organisms.

Pretreatment

Use of processes to remove or reduce pollutants from non-domestic wastewater before discharging it to the wastewater conveyance system. Also referred to as source control.

Primary treatment

The first phase of wastewater treatment in which solids are removed through gravitational settling.

Secondary treatment

The second phase of wastewater treatment that uses aeration (adds oxygen through mixing) and microorganisms to further remove dissolved and suspended organic matter remaining in wastewater after primary treatment.

Tertiary treatment

A third phase of wastewater treatment in which most of the remaining pollutants are removed from effluent (water) following secondary treatment. The processes used can include sand filtration and membrane filtration.

Thermophilic digestion

Biological degradation process where the temperature in the digester is maintained within the range of 120-140oF (50-60oC).

Ultraviolet Disinfection (UV)

The use of ultraviolet light to kills bacteria and other microorganisms in water and wastewater. Typically a final treatment step.

Units

Wastewater