- Note floc size, density, and filaments - compare to "normal" system levels (100x)
- Free bacteria and pin floc (best seen at 400x)
- Now look for indicator protozoa (amoeba, flagellates, ciliates, and stalk ciliates)
- Any higher life forms such as rotifers or worms
- Finally, anything unusual or big changes from previous exam
Microscopic exam should be performed daily or every shift by operators. When I say microscopic exam, I am not referring to filamentous bacteria ID or using any stain procedure. Instead, use a decent quality microscope (can be phase contrast or more simple light microscope) and have the operator look at a sample at 100x and 400x magnification (10x & 40x objectives). Use a standard transfer pipette to place a small amount of fresh MLSS on a slide. If you have a lagoon system, you will need to use a centrifuge to collect sufficient biomass to observe. Here is what should be noted - I promise it takes less than 30 seconds:
Plug-flow systems are normally represented by a pipe with flow going in one direction towards the effluent. Many of our common systems operate in plug-flow or close to plug-flow reactor design. The most prevalent being oxidation ditches and what I call tightly baffled activated sludge where the flow runs through narrow, long channels.
Let's recap the benefits of plug-flow:
The SV30 test uses a dedicated settleometer or 2L graduated cylinder to measure settling velocity and compaction in wastewater treatment biomass. (Note - always use the same size cylinder or settleometer to run the tests). To account for changes in MLSS concentration, the SVI takes the SV30 number and divides by MLSS in grams (some facilities use MLVSS in grams) - just use the same divisor each time.
Now for the SVI or SV30 being too low. Usually compact sludge is a good thing - it means no bulking and clarifiers with not solids carryover. However, if sludge settles too quickly or compacts too much there can be problems including turbidity, recycle (RAS) system troubles, and occasionally floating fines causing effluent TSS problems. Usually the problem is "Old Sludge" where lower F/M conditions over the long term result in bacteria consuming the extracellular polymer substances (EPS). Once the EPS percentage drops:
How do you investigate and fix the problem
A "milky" water usually means that you have an emulsion forming. Emulsions are insolubles such as grease, oils, or fats suspended in the water. Surfactants with non-polar and polar ends attach to the oils and water creating micelles. Each micelle in the milky water case contains oil attached to the non-polar end of the surfactant. The polar end of the surfactant keeps the non-polar oils suspended or dispersed in the water phase. It is the dispersed oils in this case that cause the milky appearance - interestingly milk is a suspension of fats and proteins in water hence the appearance.
Foaming in this case is caused by the surfactants and is usually stable and light in color. Anti-foams tend to work well on surfactant foams.
And remember that removing grease in the WWTP is important because:
Limited water exchange, high stocking density, and high protein feed to maximize growth rates; modern intensive aquaculture ponds often have problems with ammonia, nitrite, and other pollutants that stress the animals and open the door to disease. With several requests for an immediate ammonia response in problem ponds, I wanted to detail how to prevent the problem by good maintenance and how "nitrifiers" or AOB with their short shelf life and refrigeration requirements are not a good thing to add in almost all ponds.
First, ammonia in aquaculture comes from problems in the pond nitrogen cycle. As in nature, decaying animal wastes and excess feed (found in the pond bottom sludge) convert from organic nitrogen into ammonia. Ammonia can kill an aquaculture pond outright while still at less than 10 mg/L. Even at "manageable" levels, ammonia stresses the organisms which lowers feed conversion rates and weight gain.
Ammonia can be removed from water in several ways from greatest to least important
Key point is to monitor the pond for pH, Dissolved Oxygen, Sludge Layer frequently. If stocking at high density, adding microbes early on in the grow out season will prevent pollution problems later in the season.
Removing biological solids and insoluble compounds requires microbes to form floc or biofilms. Many desirable wastewater microbes prefer to exist in a biofilm matrix. Extracellular Polymer Substances (EPS) are the glue in biofilm and floc. Consisting of polysaccharides, proteins, DNA, and humic substances, EPS can be either attached to the cell (capsular) or free in solution (non-capsular). In typical floc, EPS constitutes 50 - 90% of total organic matter.
The Zooglea family of microbes was one of the first wastewater organisms associated with floc formation. While not the only producer of floc forming EPS, the Zooglea family are very common in most wastewater plants and can be the cause of non-filamentous bulking, difficult to dewater biological solids, and difficult to settle floc.
Why biofilm and floc forms:
For keeping biological solids under control, you need EPS to be present in quantities that allow for binding biological solids. It is also better to have capsular EPS - attached to the cells - over free, unattached EPS. In free solution, the EPS acts much like agar or gelatin. Increasing viscosity, entrapping water, and creating the gelatinous matrix we associate with non-filamentous bulking. So what triggers the excess non-capsular EPS production?
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