Wastewater Treatment Plant Issues – Reducing BOD and Ammonia Levels

It’s one of the key wastewater facts that facility managers need to be aware of: the chemical composition of wastewater can cause serious problems, which need to be averted. This includes aspects like the level of ammonia in the water and the BOD of the sample.

Products like Microbe Lift, provided to our customers within the Chemtech range, are intended to alleviate these issues. With Microbe Lift, wastewater treatment plants have an alternative to the often expensive and inefficient methods traditionally used to bring these problems under control.

Read on to discover more.

What is BOD, and Why is this a Problem?

BOD stands for biological oxygen demand, or sometimes biochemical oxygen demand. This term refers to the amount of oxygen that needs to be dissolved in water to break down any organic material within it properly.

The more biological material within a particular water sample, the higher the BOD because more oxygen is required. The breakdown of organic materials relies upon aerobic organisms within the water. Aerobic organisms, by their very definition, need oxygen to fulfill their biological function.

When BOD gets too high, this can be a serious problem for wastewater treatment plants. Not enough oxygen is dissolved in the water, so the water cannot sustain organic life. When this high BOD water is released into the local ecosystem, it immensely strains plant and animal life, eventually suffocating oxygen-dependent organisms. This can result in ecological disaster and may see wastewater treatment facilities falling foul of regulatory guidelines and requirements.

A high biological oxygen demand can also indicate high carbon dioxide levels in the water. This can be highly corrosive, significantly damaging infrastructure and systems within the water treatment facility.

What are Ammonia Levels, and Why are they a Problem?

Ammonia is produced by the breakdown of amino acids and proteins within the wastewater, resulting in high levels of this toxic chemical compound. As traditional water treatment processes, such as the deployment of activated sludge systems, tend to involve the use of large volumes of organic matter, ammonia levels can build quickly within the treatment facility.

This is a problem for several reasons. Firstly, ammonia is toxic and corrosive, as is the compound it forms when reacting with water: ammonium hydroxide. When the ammonia levels get too high within wastewater effluent, the water can corrode and damage critical pieces of infrastructure, significantly reducing their usable lifespan. The water can also cause significant damage to local ecosystems, killing plant and animal life. This sort of ecological damage will be heavily penalized by the authorities.

In addition to this, ammonia significantly increases the BOD of the water. Chemical reactions involving ammonia within the wastewater require oxygen as a reactant. Therefore, higher levels of ammonia in the water increase the oxygen debt.

Reducing BOD Levels in Wastewater

One of the wastewater facts managers need to remember is that high levels of organic matter — dissolved solids, in particular – will increase biological oxygen demand within the wastewater sample. So, removing these solids can help significantly reduce the BOD level in the released water.

Mechanical screens can be effective here. These screens remove suspended solids within the water, separating them from the wastewater mixture during treatment. The resulting solids can be scooped or filtered out of the system.

While this will work to remove some of the oxygen demand, it may not always be enough to eliminate it completely. Facility managers may need to deploy other methods alongside mechanical separation as they work to bring oxygen demand down to an acceptable level.

Removing Ammonia from Wastewater

Ammonia levels can be reduced through a process of nitrification. This means using biological organisms that carry out an oxidation reaction involving ammonia within the water, leaving nitrates that can be more easily eliminated from the effluent. However, this is not always sufficient, as extreme ammonia levels can essentially overwhelm the biological organisms within the water sample, meaning a significant amount of ammonia remains untreated.

Instead of nitrification, facility managers can use an ammonia stripping process, which removes the nitrification step from the treatment procedure. Ammonia stripping involves raising the pH of the wastewater to between 10.8 and 11.5, generally through the addition of lime, caustic soda, or another form of alkali. A desorption reaction occurs at this higher pH level, and ammonia gas is produced rather than ammonium oxide.

As ammonia gas will automatically separate from the liquid of the wastewater solution, removing the ammonia from the sample and reducing the level of this dangerous compound is much easier. This is markedly different from ammonium nitrate, which will remain suspended within the solution and can be difficult to remove.

This method does require significant amounts of resources, however. The facility will need to invest in infrastructure like ammonia stripping towers and keep these towers powered up during treatment. This may be difficult for some facilities to achieve.

Chemtech’s Alternative for Reducing BOD and Ammonia Levels in Wastewater

At Chemtech, we understand that controlling ammonia levels and BOD in wastewater can be challenging. We also recognize that investing in infrastructure like ammonia stripping towers is also beyond the reach of many facilities, which may be operating on tightly controlled budgets.

This is why we provide the Microbe Lift product. Microbe Lift offers a range of water treatment benefits, including reducing ammonia levels and bringing down total suspended solids (TSS) and BOD levels. Municipal facilities have already achieved significant results when using Microbe Lift.

To discover more about the Microbe Lift product and other Chemtech wastewater solutions, contact our team today or browse our product catalog.