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Session 03A: Wastewater Process: Planning & Compliance - Livestream
10:30am - 11:15am
What? When? How Sensitive? Evaluating Capacity At King County’s Three Regional Plants
1Brown and Caldwell, United States of America; 2King County Wastewater Treatment Division, United States of America; firstname.lastname@example.org
To protect public health and deliver reliable clean water services while accounting for changes in the service area, King County Wastewater Treatment Division (WTD) updates its projections of wastewater flows and loads every 10 years and evaluates their impact on overall treatment plant capacity. In 2014, WTD noted that influent loads were increasing more quickly than flows. Recent water conservation efforts have reduced the amount of potable water used on a per-capita basis. These reductions in water use directly impact wastewater flows, but not loads. As a result, influent concentrations are higher than the design values. Comparing the flow and load projections with the current rated capacities for each of the County’s three regional plants (South, West Point and Brightwater) shows that the rated flow capacities will be reached after 2035 whereas the rated loading capacities will be exceeded within the next 10 years.
To identify potential capacity limitations and their timing by process within the three plants, WTD undertook an in-depth capacity evaluation for all major processes. The evaluation accounts for plant-specific wastewater characteristics, existing regulatory requirements, operating configurations, and process performance. Sensitivity analyses were conducted for each plant to assess the influence of various critical parameters on unit process capacities. Some unit process capacities were found to be highly sensitive to changes in certain parameters. For example, at West Point, capacity of the aerators in the high-purity oxygen aeration basins could change significantly at different target dissolved oxygen concentrations. At both West Point and Brightwater, taking one digester out of service for maintenance was found to have significant impact on the timing of the digester capacity limitation. This analysis provided WTD with an understanding of the timing for when unit process capacity limitations may be experienced to inform system-wide treatment planning.
11:15am - 12:00pm
Dairy Cows Speak a Different Language: Jerome’s Journey to Wastewater Compliance
Jerome's wastewater treatment plant is unique in that several dairy products processing facilities deliver most of the loading to the treatment plant. This dairy processing brought significant revenue to the City, at the cost of large fluctuations and high loading at the treatment plant. Seeking resolution to repeated discharge permit violations caused by the high loadings, the City and the Environmental Protection Agency entered a consent decree. The City of Jerome and Keller Associates worked quickly to assess the treatment system and evaluate compliance options for the best treatment of the high-strength wastewater. A phased approach to improvements allowed the City to promptly reduce additional non-compliance risks while further upgrades were designed and constructed.
Phased upgrades at the treatment plant were completed approximately a year ago. These upgrades incorporated approximately five years of construction and a total cost of about $35 million – the largest project in the City's history. This wastewater treatment project successfully reused/rehabilitated a significant portion of the existing plant and included the construction of 24 new treatment/conveyance structures. Plant compliance during construction was challenging as all unit processes were disrupted. This presentation will focus on the approach and results – during design, construction, and post-construction – that addressed Jerome's high-strength dairy wastewater and prepared them for sustained compliance.