Water temperature affects most aspects of wastewater pond performance and can be a reliable predictor of water quality. Seasonal temperature changes will impact a wastewater pond’s performance. Colder temperatures, in particular, can cause the following changes in your wastewater pond:
Falling temperatures cause the surface layer of the pond to cool and become denser. This heavier water sinks and moves the warmer water from the bottom to the top where it also cools. This is known as a pond ‘turnover’.
Warmer influent coming into the pond may ‘short circuit’ across the surface of the pond and out the effluent without being fully treated. This is especially common if the pond isn’t adequately mixed through wind or aeration equipment.
Increase in BOD
Microbial activity is reduced in cooler temperatures, and as both bacteria and algae slow down their digestive processes BOD can build up.
A slowdown in biological activity will also reduce digestion of sludge allowing settling solids to accumulate on the bottom of the pond.
Loss of Nitrification
Nitrifying bacteria prefer warmer water and virtually stop work at the freezing point of zero degrees. They have a thin cell wall which makes them susceptible to chemical attack so if a chemical slug is experienced during Winter it can be difficult to get their numbers back.
Reduction of Phosphorus Removal
Phosphorus removal is also temperature sensitive and reduces during cooler temperatures.
Promotes Conditions for Spring Pond Turnover
In Spring, cooler water heads back down to the bottom and warmer water creates a burst of biological activity. This can release odorous gases from the bottom which can linger for days. It can also cause blooms of algae and/or weed as water rich in nutrient from interaction with sludge has now moved to the warmer surface layers.
So, what can you do to prepare yourself for some of these challenges?
Check and Maintain Equipment
If you have aeration that requires seasonal maintenance, do it the cooler months when pond activity is reduced.
Mix The Entire Pond
Thorough mixing will prevent short circuiting and thermal stratification. In turn, this will create a homogenous water temperature, preventing spring turnover and its associated problems.
Increase Dissolved Oxygen
Microbes require DO to digest BOD and stop it building up as sludge. Aeration equipment should be used year-round in wastewater ponds. Wastewater aerators should not only aerate but also mix water efficiently. The MARS aeration system or Airolator Aquarian Commercial are examples of effective aeration and mixing equipment.
MARS Sub-Surface Wastewater Aeration Systems
The MARS aeration system is well suited to Australian conditions and is a good choice due to our high-power costs. These diffused air systems combine coarse bubble diffusers to keep solids suspended and fine bubble diffusers for high oxygenation. Pumping air requires less power than pumping water so running costs are low compared to larger surface aerators. Equipment maintenance is onshore which also helps keep lifetime costs low.
Airolator Aquarian Commercial Surface Aerators
The Airolator Aquarian Commercial is small and lightweight with no lifting equipment required. These systems are versatile and in larger ponds multiple units can be used. This approach has several advantages over larger surface aerators as multiple locations creates better mixing and multiple aerators also means equipment can be cycled on and off during times of year where temperature or influent loads don’t require full aeration/mixing. This offers cost savings for both power consumption and longevity of equipment.
Vitastim Nitrifiers are a super concentrated blend of multiple species of nitrifying bacteria. They are effective in quickly bringing nitrification back online after a chemical slug or equally effective at increasing nitrification rates and restoring balance during cooler temperatures.
Managing a wastewater pond in Australia is a year-round activity. Giving your pond some love during winter will reward you with less problems during the warmer months.