8 Growth Pressures and Their Impact on the Microorganisms in Wastewater Treatment

Danielle Sharp, Senior Microbiologist for EBS, presented at the Gainey’s Concrete Products Wastewater Conference focusing on the importance of the 8 Growth Pressures and their impact on the microorganisms in wastewater treatment. She also spoke about the value of interpreting laboratory testing and a real-world case study.

Role of Microorganisms

Bacteria and HLF are the microorganisms that do the work with the majority of the conversion of BOD into solids completed by the bacteria. However, HLF does contribute to the reduction of BOD as well. Another major point is HLF are indicator organisms that indicate healthy system conditions.

The bacteria carry out the conversion of soluble organic material (BOD) into insoluble cell matter (TSS).

Role of Higher Life Forms

In addition to the single cell bacteria, the biomass will contain other microorganisms. These organisms are collectively referred to as higher life forms or indicator organisms. As the system matures or stabilizes, the type and relative abundance of the higher life forms will change. By monitoring the higher life form population, you can draw many conclusions regarding the overall health of a particular system. Higher life form distribution tends to be very plant specific. What looks normal in one facility may not be typical for another.



  • • Feed off of free swimming bacteria and bacterial floc
  • • Reduce effluent total suspended solids
  • • Provide information regarding the health and stability of the system
  • • Number and distribution is dictated by available food source (prey density) and environmental factors, such as dissolved oxygen, temperature and toxicity

Know what is typical for your WWT system!








Case Study Sludge Settle-ability

The case study presented showed the effect that nutrient deficiency could play on sludge settle-ability. The introduction of sufficient nutrients in the system directly caused a decrease in filament abundance, which in turn improved the compaction of the sludge and SVI values.

8 Growth Pressures







EBS identified eight areas that are critical to how well your system will perform. We call them the 8 Growth Pressures all affect your sludge quality.

Through routinely monitoring a wastewater treatment system using just a few key tests, valuable insight can be gained about the system’s performance. EBS routinely performs testing for various types of industrial facilities around the country, providing consulting expertise through laboratory data.

Key Points

  • Biological wastewater treatment is a natural, living process
  • Monitoring the 8 growth pressures is key
  • Knowing your system’s normal operations can help you better navigate upset conditions
  • You cannot control what you do not measure


Learn about the microorganisms in your wastewater treatment system.