- Fill your settleometer with 25 - 50% MLSS taken from the aeration basin. Make sure you mix the sample first to ensure you have solids all suspended.
- Use effluent or tap water to fill the settleometer. Again mix the MLSS/Water blend to suspend the solids.
- Start 30 minute timer. Note sludge level at time 5, 10, 15, 20, 25, & 30. Adjust dilution to have SV30 settled solids reading between 150 - 300 ml on the settleometer. After settling, note floating solids and pin-floc in the supernatant. You should also let the solids continue to compact for 2 - 4 hours. Evaluating the compacting solids gives information about how concentrated the RAS solids will become in the secondary clarifier.
- For reporting purposes and SVI calculations, remember to multiply by your dilution factor.
When you have MLSS above 5,000 mg/L, SV30 tests often have solids with a very narrow band of supernatant. This can make it difficult to diagnose problems with pin floc, settling velocity, and compaction. If you see the water phase of less than 20% of the settleometer, the diluted SV30 test may prove useful. Here is how to run a diluted SV30:
Most of the work on Aerobic Granular Sludge (AGS) has been either with synthetic wastewater (lab studies) or in domestic wastewater installations. In these cases, the AGS forms into irregular but tight granules that settle rapidly. AGS has great potential because:
The authors created an excellent graphical abstract for evaluation of AGS appearance with different influents.
Pronk, M., Abbas, B., Al-zuhairy, S.H.K. et al. Effect and behaviour of different substrates in relation to the formation of aerobic granular sludge. Appl Microbiol Biotechnol 99, 5257–5268 (2015). https://doi.org/10.1007/s00253-014-6358-3
Bacteria form biofilms (in wastewater we call this floc) for many reasons. Among the most important is to protect the individual cells from the surrounding environment and capture/concentrate nutrients necessary for growth. Montanta State University actually has a group focusing on biofilms - http://www.biofilm.montana.edu/
The researchers at Montana State have created a great infographic on why biofilms are important that I want to share. It is a very good read.
Food to microorganism ration has long been used to operate activated sludge sytems. I will start out saying calculated F/M should not be the only operational parameter you shoud evaluate. F/M has good and bad points that should be considered. As with all wastewater control information, you should use F/M with other data points and knowledge of your treatment system.
In addition to F/M consider the following parameters that you probably already run
When we use the term "bugs" for our wastewater microbial poulation, we are simplifying what is actually a community of thousands of microbial genera. The organisms form functional groups that ensure complete waste treatment. An important part of this action is the formation of Extracellular Polymeric Substances (EPS). The EPS is the glue that holds cells in a biofilm or floc. EPS is composed of polysaccharides, proteins, enzymes, and DNA that form a matrix containing bacteria, particulates, and stored organic compounds. Even filamentous bacteria are needed for "best" quality floc. As long as the filmanets are functioning in their macrostructure role and inside the floc, the flilaments are beneficial. So maintaining EPS at proper composition and levels is key to separating the biomass from treated effluent even if you use clarifiers, DAF, MBR, or other solids separation system. Now for a few common reasons why secondary polyer demand can increase:
Keeping stable Ammonia Oxidizing Bacteria (AOB) and Nitrite Oxidizing Bacteria (NOB) populations in wastewater can be a challenge. Some factors that can result in population instablity include:
What I have learned or seen proof of working during the testing
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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