Intensive aquaculture relies on stocking ponds heavily and using both mechanical aeration and feed addition to produce large amounts of seafood. While increasing yields exponentially over natural ponds, this process has problems with off-flavors, diseases, and low feed conversion that can be traced back to buildup of pollutants and pathogenic microbes.


While I have long focused on treating wastewater, Aster Bio was asked to investigate if microbes could improve productivity in shrimp farms and reduce off-flavors in catfish farms. We looked at the wastes causing the pollution including ammonia/nitrite buildup. Additionally, we considered how beneficial microbes could enhance feed conversion and competitively exclude pathogenic microbes. After studying the problems and surveying ponds, we tested multiple formulations to see if adding microbes could changes pond ecology and enhance yields. The results are below:

Anammox is one of the newest technologies for treating both ammonia and nitrite in wastewater. In the past operators running systems with long sludge ages noticed that nitrification did not consume as much oxygen and alkalinity as was calculated by normal Nitrosomonas and Nitrobacter ammonia oxidation. Furthermore, the denitrification process to remove nitrate/nitrite had less of both compounds entering the anoxic/anaerobic zone. What was happening?
Anaerobic Ammonia Oxidation (ANAMMOX) is pictured in the nitrogen cycle graphic at left. The process is as follows (forgive the lack of subscript):

                                                                   NH4 + NO2 -->  N2 + 2H2O

The microbes responsible for ANAMMOX conversion of ammonia and nitrite have been recently isolated and we are still in the process of understanding their microbiology in wastewater. Here is what we know:

The typical flagellate found in wastwater treatment plants appear as small ovoid shapes that move in the liquid phase surrounded by much smaller free bacteria. Using a single or multiple flagella, long whip-like structures, for motion; these single celled protozoa are one of the first indicator microbes seen in a wastewater treatment system. In the system they consume the free floating bacteria cells and adsorb some soluble organics for their nutritional requirements. (Note: there are some photosynthetic flagellates found usually in ponds, lakes and streams but not as common in wastewater.)

You see flagellates at the early stages of wastewater treatment or when there is log phase growth of bacteria. In lagoon systems, you will often find flagellates predominating near the inlet where dissolved oxygen is low & soluble BOD high. If seen near the effluent, this indicates some type of upset condition. Common triggers include - (1) high hydraulic loads, (2) increased organic loadings, (3) pond turnover, and (4) problems with dissolved oxygen concentrations.

In activated sludge or fixed film systems, the sudden appearance of flagellates can indicate an increase in organic loadings or follow a toxic event that killed off significant portion of the living bacteria found in the MLVSS or biofilm. Either event merits further investigation into what is causing the increase in flagellate populations.

Can bacteria be used to prevent grease accumulation in problem sewer lines? During field testing using microbial cultures with either a metering pump or manual dosing, Aster Bio was able to get some very good proof that microbes can work in the confines of municipal sewers in preventing grease accumulation.

The trial pictured below shows a problematic sewer line down stream from several quick serve restaurants. The line was cleaned on a regular basis using jetting and various cleaning solutions. The problem is the cleaning solutions and jetting just push a big slug of grease to the lift station and sewage treatment plant. Aster Bio tested our products to see if microbes could successfully colonize the pipe walls and actually degrade the grease. The results are in the photo below:

Restaurants especially busy quick serve and fast casual work diligently to clean and disinfect all surfaces in the store. Even with cleaning and attention to detail, there are often rancid odors in certain areas and "fruit flies" (actually drain flies) that seem to appear out of nowhere. Couple this with the occasional emergency plumber call out for grease clogged floor drains and we have a significant problem for restaurant managers.

I was called in 20 years ago by a chicken QSR to develop a product to treat their grease trap. They faced high pumping costs yet still needed to pump out the traps every two weeks for control of odors and grease discharges to city lines. While walking through numerous locations before opening hours, I noticed the odors and discovered they often had two plumber call outs per month for clogged floor drains. This led to a new microbial/enzyme application that had the potential to solve multiple problems.