From Burian A, Et Al. Predation increases multiple components of microbial diversity in activated sludge communities. Protozoa are eukaryotic residents of wastewater treatment plants that serve as primary predators of bacteria. (Some protozoa are free-living and not predatory). Since protozoa are much larger than bacteria and easily recognized by shape and motility, we use their diversity and populations as indicators of system health.   Since the protozoa “eat” bacteria and bacteria are the organisms that remove pollutants, are the protozoa detrimental to treatment efficiency?   P ..read more

From Guoqiang Liu et al. Formation of filamentous microorganisms impedes oxygen transfer and decreases aeration efficiency for wastewater treatment This topic was brought to my attention last week when a facility that I am working with noticed that Thiothrix filaments appeared to be reducing oxygen transfer efficiency in the aeration basin. While low D.O. promoting filamentous growth is well known, I was not familiar with how much filamentous bulking can reduce OTE.   Oxygen Transfer Efficiency (OTE) refers to how effectively oxygen is delivered and dissolved in water under specific con ..read more

Archaea are not bacteria! While still unicellular, they are as different from bacteria as a they are from you (a Eukaryote). Some cool facts about Archaea: First isolated from extreme environments where they compose a larger % of the total biomass. Extreme temperatures, salinity, pressures, and pH – think deep sea vents, highly anaerobic sediments, and acid mine waters. In wastewater, methanogens are archaea. They are found in aerobic digesters, digestive tracts, and deep within wetland soils – oxygen is toxic to these organisms. Ammonia Oxidizing Archaea are responsible for much ammonia ox ..read more

Slide from Biofilters and air pollution control by Aabid Mir (2013) Biofilters consist of a bed of organic material, such as compost, wood chips, or synthetic materials, that provides a substrate for the growth of microorganisms. The media's surface area is crucial for microbial colonization and the adsorption/removal of odorous compounds.   Microbial Colonization: Microorganisms, including bacteria and fungi, naturally colonize the media in the biofilter. Specific microbial strains are selected for their ability to metabolize and break down hydrogen sulfide and volatile organic acids ..read more

Filamentous bulking related to organic acids can be a problem in wastewater systems. ​Organic acids are formed under anerobic conditions where bacteria grow under what we call fermentative conditions (bacteria using organic compounds as a terminal electron acceptor to get energy). Common sources of organic acids include – collection systems, equalization tanks, sludge layers in lagoons, and even anaerobic digesters. If there are sulfides present, organic acids are a key part of what we call “septic” water.  Biological nutrient removal systems require organic acids to function properly ..read more

Keeping a stable, healthy nitrifier population in wastewater treatment challenges many operators. As slow growing organisms, both Ammonia Oxidizing Bacteria (AOB) and Nitrite Oxidizing Bacteria (NOB) prove susceptible to washout when environmental conditions slow their growth.  From experience, it is more often a slow decline in AOB/NOB populations rather than an acute toxicity event (kill) that increases effluent ammonia. When you start to see effluent ammonia increasing, head off the problem and perform the following steps. Step 1 - Determine what caused the problem by looking at infl ..read more

MBR systems replace traditional secondary clarifiers (gravity separation) with a membrane containing pores. The small size of the pores - microfiltration or ultrafiltration - separates solids from the discharged water. MBR technology has come a long way in the past 20 years and is now a viable alternative to clarifiers. For those not familiar with MBR systems here is a quick summary of strengths and weaknesses Strengths Allows for higher MLSS concentrations than conventional activated sludge (CAS) Total separation of solids and ultrafiltration improves effluent quality - ability to meet stri ..read more

Aster Bio’s molecular testing capabilities include running 16s rRNA to conduct a total bacterial and archaeal (when needed) census for wastewater systems. The use of high throughput sequencing allows us do dive into what is doing the work in a biological treatment system. It identifies both good and bad actors and gives early warning of potential problems. When we first introduce this technology in 2017, the challenge was speeding up test turn-around-time (you don’t want to wait 4 – 6 weeks for operational test data) and reducing test cost which was much higher than standard operational tests ..read more

Step-Feed aeration basin to reduce impact of high soluble BOD (septic) wastewater. A sudden color change to gray or black accompanied by odors is often called septicity or septic wastewater. Septicity can be caused by several factors and environmental conditions, so let's review what makes wastewater septic and how to correct septic conditions. How to detect septic wastewater Dark gray or black color Negative ORP (Redox) & D.O. absent Odors from sulfides and/or volatile organic acids Color is usually the first thing noticed by operators as it is a very distinct from normal wastew ..read more

Biological Oxygen Demand (BOD) tests measure oxygen use by aerobic microorganisms growing on samples. In a sealed bottle, you measure oxygen consumption by a seed over usually 5 days under strict temperature control and darkness (to control for photosynthesis by algae).  Things that can confuse test results Insoluble organics – COD and TOC tests pick this up. But insoluble organics do not usually cause BOD test problems. Recalcitrant compounds – bacteria don’t grow on these. This means that the test misses these compounds and they do not show up in the test. .In bottle nitrification by ..read more