In an earlier post, I discussed the importance of biological polymers - extracellular polysaccharides (EPS) and the other extra cellular materials that make up the "glue" that hold floc together. This glue action binds bacterial cells and large particles into a particle size that readily settles in final clarification. It should be noted that floc is the same as a biofilm with respect to microbial ecology.
The extracellular materials help the organisms by providing a protected, more stable environment, help prevent predation, improve access to nutrients and micronurtrients, and bind insoluble materials for later breakdown/utilization by the microbes.
For the past week, I have been screening a high soluble BOD wastewater stream (BOD5 of 4,200 mg/L) with high levels of starches, organic acids, and proteins. I was looking for ways to increase floc formation and improve water clarity, lower TSS before discharge. After searching various microbes for blending, I looked for strains with the capability of producing a cationic, high molecular weight polymer that remains attached to cell. The optimal strains would also produce this polymer during log growth which is a not commonly seen.
Adding these cultures to existing biomass created big changes in a 40 hour study. The results were easily seen in photos.
Stepping a back from my normal biological only part of waste treatment focus, I am going to consider the entire waste treatment system from an operational perspective. During daily operations, operators do not often look at average chemical usages (polymers, odor control, anti-foam), sludge wasting volumes, sludge going to off-site disposal, nutrient additions, or energy usage. As a result, often treatment costs tend to increase slowly and there is a tendency to stick with existing technologies without regard to costs or evaluating better options.
Therefore, I believe it helps for both operators and managers to conduct periodic reviews or audits of the system. This can be a simple review of daily operational charts and looking at moving averages. Or, it can be a more complete audit including outside technical review - since a new set of eyes can often help see new options or question existing practices. Even with paying for outside consultation, the savings from small reductions in per unit treatment costs can quickly add up and prove valuable to extending the effective operational life of the system.
Before doing any capital investment, an audit should be performed. As there are many competing options for your equipment purchases, it is good to get an independent engineer's opinion before committing to a single technology choice.
As for frequency of audits, it all depends on the system! However, I think it is valuable to set up a dashboard with moving averages on energy, chemical, loadings, and volumes. This dashboard will provide everyone from operators to management with a quick summary of what is taking place and trigger questioning if something suddenly increases above expected ranges.
In areas with available land, facultative ponds are an effective, low-cost way to treat wastewater. Facultative ponds have aerobic, anoxic, and anaerobic zones all within the same basin depending upon water depth. Dissolved oxygen is provided by the surface air/water interface, wave action, and in summer months - algae!
While often considered a problem during summer months when an algae bloom can cause effluent TSS issues, the algae is important in providing oxygen and removing nutrients (nitrogen & phosphorus) from the wastewater. As an advocate of regular microscopic exams to check the microlife of the pond, it is good to take fresh samples from the pond and centrifuge to get concentrated solids to examine. Besides the protozoa and free bacteria, note the algae that are present. Changes in algae type - can indicate changes that can result in a bloom. Most of the water quality issues are caused by blooms of cyanobateria or blue green algae that can rapidly generate in water and cause problems with odors, pH swings, and TSS.
Often we do microscopic exams to identify filaments and other causes of bulking. In general, the reports give information on the top filaments or bulking agents and the conditions associated with their dominance in biomass. What is not often done is to take a step back and look at the ecology associated with the increased populations of filaments or high levels of viscous polymers that cause bulking.
What is interesting is that the causes of both filaments and viscous bulking are similar - it is just the mix of factors that determines if the system experiences which problem and to what extent.
The most common factors are:
No matter how much we try to segregate storm water from true waste water, heavy rains create increase flows to wastewater systems. Storm water should often be treated when it contains hydrocarbons, fertilizer and other components of runoff; but in the case of floods - we are talking about high volume, low COD/BOD waste. In a worse case scenario, influent flow increases to a level where a substantial portion of the microbial biomass is washed into the effluent. Below I will give the options on how to prevent or quickly correct this problem:
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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