Biological wastewater treatment has been a hot bed of innovation in the past ten years. Much of the innovation is being driven by new permits, a desire to recycle water, lowering energy use, and making systems more efficient. Below are some of the interesting projects that I have been fortunate to see in application.

Molecular Testing​​ 
Since I started working with wastewater molecular testing about seven years ago, it has developed from a curious novelty to a powerful operational control tool. Molecular or DNA testing can see slight changes in important populations including AOB/NOB, PAO/GAO, Filaments, Nocardia, Methanogens, and SRB. An example with AOB/NOB is a warning of nitrifier stress before effluent ammonia starts to increase. This technology continues to develop and will become even more useful as our knowledge increases.

Nanobubble & Microbubble Aeration
Maintaining sufficient D.O. in aerobic treatment systems is always a challenge and expensive. The development of new extremely efficient systems for oxygen transfer coupled with resistance to fouling is going to lead to improved aerobic systems. In field testing, I have been amazed with how much D.O. can be maintained and transferred while using less power than standard diffuser systems. 

Granular Sludge
Current systems rely on suspended floc or biofilms for treatment. First seen in anaerobic digesters, granular microbial aggregates can also develop in aerobic treatment systems. Key benefits are:

• Compact footprint as you maintain much higher levels of biomass in the system. 
• Having Aerobic, Anoxic, and Anaerobic zones within the granule - allowing for simultaneous nitrification/denitrification in one treatment zone.
• Fast settling rates reduce likelihood of hydraulic washout.
• Appears to be adaptable to existing systems.

Nitrogen and phosphorus from non-point sources have major implications for hazardous algae blooms. In natural low nutrient waters, algae provide both oxygen and primary food source for aquatic life. As we increase nitrogen and phosphorus concentrations, the delicate balance between algae varieties, protozoa, metazoa, and higher aquatic life becomes disrupted.

An interesting solution that may have application to waste water treatment in locations with available land is detailed in an article from the University of Illinois College of Agricultural, Consumer and Environmental Sciences published in Science Daily. Researchers detail how using wood chips in flow channels can remove much runoff water nitrogen by converting it to nitrogen gas. 

https://www.sciencedaily.com/releases/2021/04/210415170716.htm​

Industry publications and journals focus on newer technologies such as MBR, Granular Activated Sludge, and other advanced systems. However, much of our wastewater is still treated in lagoon systems and these systems still have an important part in treating wastewater. What most people don't realize is that lagoons can also be upgraded to meet higher loadings and more stringent effluent permits.

Some examples of lagoon upgrades include:

• Adding advanced aeration & mixing which reduces short circuiting, anoxic zones, and maximizes biological activity. I am especially interested in new microbubble/nanobubble technologies that improve oxygen transfer with less utility costs.
  
  
• Opportunity to enhance performance by adding MBBR into lagoons. The MBBR media develops biofilm that remains suspended in the lagoon and treating pollutants. If you see this as lowering the F/M or increasing MCRT for microbes in the system, you are correct.
  
  
• Installation of smaller advanced treatment modules to remove ammonia or phosphorus while using the lagoon for primary BOD/COD reduction.

A subset of industrial wastewaters including pulp & paper have lower than optimal C:N:P ratios. To ensure proper bacterial growth, these facilities often add various nutrient blends to supplement both N & P. What happens when they do not supplement macronutrients at optimal levels or even add not nutrients at all?

We have long known that deficient macronutrients often impacts floc formation and the filament/floc forming organism balance. But what happens with the actual microbial makeup in the biomass. Molecular testing allows for conducting a total microbial census and we can compare similar systems with and without added macronutrients.

Diazatrophs are microbial organisms that use N2 gas - present at approximately 80% of our atmosphere - to provide nitrogen needed for cell growth. This reaction is most described in agriculture with legume crops where the microbes grow in root nodules. In wastewater, diazotrophs include a diverse mix of organisms including Rhizobia, Rhodopseudomonas, Frankia, Klebsiella, Azotobacter, Paenibacillus, and many cyanobacteria genera. Some of these organisms are floc forming and desirable in wastewater but others like cyanobacteria can create water quality issues.

In systems adding macronutrients, operators want to add sufficient N & P to keep a healthy, floc forming microbial population but not overdose nutrients. In the past, nutrient dose was based on finding N & P residuals in the effluent and maintaining these at target residuals. With molecular testing, we are now able to monitor for the presence of AOB/NOB (feeding too much nitrogen) and diazotroph populations (if in excess, you have insufficient nitrogen).

Aster Bio has been testing an increasing number of BNR plants with excellent phosphorous removal efficiencies. Our testing - Environmental Genomics™ MCA - is a total microbial census of MLSS with relative % of each genera. Using this molecular sequencing technology, you can see key differences among microbial populations based on system design and operation. 

Data from MCA Test
We use high-throughput sequencing of the 16s region to conduct the microbial census. The sequencing produces over 100 MB of data per run, so making it useful also means summarizing the data in a convenient table. Below are two different runs from a healthy BNR system with biological phosphorus removal and a conventional activated sludge system. The table presentation gives % of total reads for common functional groups - of course there is a lot of data behind this summary that is also interesting.

Key Differences
The Non-BNR systems of course have fewer PAO/GAO populations. The "Bulking" column is composed of Zooglea/Thauera genera. These genera are common bacteria that can form good floc, denitrify, and degrade a wide range of organic compounds. Under certain influent conditions, the bulking group can produce excess EPS that causes non-filamentous bulking.

BNR system testing reveals that the PAO/GAO cultures are inversely related to the Bulking genera. I have also noted that the BNR systems also tend to have more known filamentous bacteria genera present.