Wastewater Treatment

WASTEWATER TREATMENT PROCESSES

Wastewater collection and treatment have been developed and perfected using some of the most technically sound biological, chemical, mechanical and physical techniques available. Today’s public health are protected better today than ever before. The FUNCTION of a wastewater treatment plant is to speed up the process by which water cleanses itself – it’s essentially the same as what occurs naturally in a lake or stream.

Wastewater treatment processes involve 3 major steps:

1. Preliminary
   Screens, settling tanks and skimming devices are used to separate sand, grit and larger debris from the liquid.
2. Primary
   Tanks, large rakes on the bottom and skimming devices are used to remove 35-60% of the pollutants (from sludge to scum which are forwarded to digesters).
3. Secondary (Biological and Settling steps)
   To remove the 85-90% of the remaining solid materials that are floating on the surface, dissolved in the water, the biological process uses air to stimulate the growth of bacteria and other organisms to consume most of the waste materials, such as nitrogen and phosphorus.
   Settling:

To learn more about the full wastewater treatment process, watch the various videos on this page.

WASTEWATER SAMPLING AND TESTING
Technicians conduct regular tests to monitor the water entering the plant and to ensure that the plant is meeting its requirements to produce clean water. Samples are taken daily and hourly, with results being reported to government agencies.

ROTATING BIOLOGICAL CONTACTORS

Rotating biological contactors (RBCs) are a fixed-film biological watewater treatment technology that was widely applied in the 1970s and early 1980s.

RBC technology consists of circular sheets of inert plastic support media attached to a shaft and submerged approximately 40% in the wastewater process stream. The shaft is rotated so that the media is exposed intermittently to wastewater and air. This provides alternate exposure of the biomass growing on the plastic support media to wastewater, thereby allowing the metabolism of soluble and particulate organics and air, thus allowing oxygen transfer.

Excess biomass sloughs off the media and settles in a downstream clarifier (not shown in the above diagram).
[RBCs can be used for BOD₅ removal, nitrification or both.]

Water Treatment Plants

WATER PURIFICATION PROCESSES

Wastewater collection and treatment have been developed and perfected using some of the most technically sound biological, chemical, mechanical and physical techniques available. Today’s public health are protected better today than ever before.

The following list provides a brief overview of the vast levels of processing that occur in a water treatment and purification plant…

1. Pre-screening: Water runs through mesh screens to remove sticks, water weeds and other large foreign objects.
2. De-Gassification: Air is used to remove odors and gasses from the water (to dissolve metal salts that can be separated and filtered out). Air is added by cascading the water down a tower, spraying it into the air or bubbling air through it.
3. Coagulation: To remove color, bacteria and fine matter suspended in the water, a precisely-controlled amount of coagulant (such as ferric or aluminium sulphate) is added to the water. The coagulant reacts with materials in the water so they stick together, forming larger particles called “floc”.
4. Flocculation: A flash mixer mixes the coagulant and water together very quickly and very thoroughly.
5. Clarification: A process (to separate the sludge layer from the floc)
6. Filtration: Water is filtered through very fine sand or sand-like materials to remove remaining particles.
7. Ozone gas injection: This is an optional treatment, which filters water through carbon granules to remove any traces of largely organic natural materials.
8. Disinfection: To remove any harmful bacteria, small amounts of chlorine are added, which is usually the most effective method. Chlorine does require contact with the water for a period of time to be effective.
9. pH Level Check: Adjustment for neutrality.
10. Stored in main pipes – ready for public reuse.

Bacterial cells that aggregate in flocculation (below).