Optimising Commercial Sewage Treatment: Insights from Ozzi Kleen’s Commercial Sizing Presentation New

On Friday, August 9, 2024, Ozzi Kleen had the privilege of hosting a Commercial Sizing Presentation at our head office. This educational session brought together environmental engineers and geotechnical consultants to deepen their understanding of commercial sewage treatment plant (STP) sizing using Biochemical Oxygen Demand (BOD) and Equivalent Persons (EP) rather than just hydraulic EP figures. By bridging knowledge gaps and providing a structured approach to STP sizing, the event aimed to streamline the design and proposal process while ensuring compliance with regulatory standards.

The Purpose of the Presentation

The primary goal of this session was to assist and educate industry professionals on correctly sizing STPs by focusing on BOD loading rather than just hydraulic loading. Many engineers and consultants traditionally size treatment plants using hydraulic EP values, which measure daily water usage per person. However, BOD EP accounts for the organic waste load generated per person, which provides a more accurate representation of a plant’s treatment capacity. By assessing the hydraulic and biological loadings, professionals can ensure that sewage treatment plants are properly designed to fulfil effluent quality standards, thereby mitigating the risk of under-sizing.

Key Topics Discussed

The presentation covered crucial concepts and practical applications related to STP sizing. Below is an overview of the key topics discussed:

Definitions and Core Concepts

• Hydraulic Load – Defined as the total volume of wastewater generated daily, measured in litres per person per day.
• BOD and BOD Loading – Biochemical Oxygen Demand (BOD) is a measure of organic matter in wastewater that microorganisms must break down. BOD loading is calculated based on grams per person per day.
• Equivalent Persons (EP) Sizing Comparison – Hydraulic EP is defined as 200L/person/day, whereas BOD EP is 70gBOD/person/day.
• BOD vs. Hydraulic Loading – Discussion on how treatment systems, such as the Ozzi Kleen RP10 and Ozzi Kleen RP50, are designed based on BOD EP and how different facilities require varying treatment capacities.

Sizing Septic and Aerobic Treatment Systems

• Septic System Sizing – Introduction to the formula for sizing septic tanks, referencing Appendix E of the SA Health (2013) guidelines. If no septic system is used, BOD EP should be increased by 40%.
• Aerobic Treatment System Sizing – A six-step framework was presented to help engineers and consultants size aerobic systems efficiently:
  1. Determine the number of people and facilities on-site.
  2. Identify the commercial activity code or standard.
  3. Use wastewater code to establish BOD loading and daily flow rates.
  4. Incorporate real flow data from utilities when available.
  5. Convert to EPs.
  6. Select reactors, tanks, and size pumps accordingly.

Application of Theory: A Real-World Example

To reinforce learning, participants worked through a practical exercise involving a school with 250 students and 35-40 staff members. The exercise required them to calculate:

• Hydraulic EP
• BOD EP
• Number of RP50 systems needed based on Hydraulic EP vs. BOD EP
• Comparing the differences between Hydraulic EP and BOD EP

Participants were given 15-20 minutes to complete the problem, followed by a guided walkthrough of the correct solution. The exercise highlighted how sizing based purely on Hydraulic EP often results in an undersized STP, failing to meet permit specifications.

Why This Knowledge Is Valuable

By equipping environmental and geotechnical consultants with this methodology, Ozzi Kleen is fostering a more efficient design and proposal process. Correctly sized STPs reduce the risk of underperformance and ensure compliance with regulatory standards. Moreover, this approach minimises back-and-forth communication between consultants and manufacturers, expediting project approvals and installations.

Wrapping Up the Day

Scott V. concluded the presentation by introducing Ozzi Kleen’s commercial STP enquiry form, designed to streamline the initial sizing and proposal process. Attendees expressed their appreciation for the insightful and practical nature of the session, acknowledging how the information provided would enhance their future projects.

Although no photos were taken, the event was highly educational and beneficial for all involved. Ozzi Kleen remains committed to supporting the industry with cutting-edge knowledge and practical solutions, ensuring Australia’s commercial wastewater management systems are designed for maximum efficiency and compliance.