Sanitary Engineering
Flow monitoring is conducted throughout the collection system to assess current conditions on a real time basis. The City has monitored flows in the wastewater system since 1975. Currently, 30 permanent flow monitoring sites are established on sewer trunk lines throughout the collection system. Additional monitoring occurs using temporary meters based on current data collection needs. Flow monitoring locations are chosen based on pipe size, location in the city, proximity to lift stations and other trunk lines, and additional factors specific to each site. The distribution of monitoring sites gives a detailed picture of the wastewater system and allows analysis beyond the recovery facilities.
Three types of flow monitors are currently in use: area velocity sensors, Flo Dar ultrasonic sensors, and LaserFlow sensors. The different sensor types allow for effective monitoring dependent on pipe and site characteristics.
Constant flow monitoring is used to establish a baseline for each trunk sewer, collection basin and the system as a whole. The data from these sites can be accessed during a high flow event to determine effects and predict response needs. After an event, the data can be analyzed to determine potential infiltration and inflow locations in the collection system and evaluate system response. Collected data is also used to determine the ability of the collection system to handle increased flows from the addition of new developments or industries.
The Lincoln Wastewater System monitors approximately 35 industrial discharges to the sanitary sewer. Through an agreement with the State, the City is required to monitor all local industries which discharge pollutants into the sanitary sewer that may cause interference or damage to the municipal sewage conveyance and resource recovery systems. These industrial users include facilities discharging conventional pollutants and metal finishers. Conventional pollutants include biochemical oxygen demand (BOD), total suspended solids (TSS), pH, and oil and grease. Metal finishers discharge regulated metals including cadmium, chromium, copper, lead, nickel and zinc. An industry may fall under either of these categories, or possibly both, depending on the activities occurring at the facility.
Significant industrial users (SIUs) are regularly sampled throughout the year as part of the billing process and to determine the waste contributions from regulated industries to Lincoln’s water resource recovery facilities. The City has implemented a surcharge billing program for facilities discharging high strength waste – those exceeding 250 mg/l BOD or 300 mg/l TSS. Sampling occurs over the course of at least one week, but typically longer, to ensure a complete and accurate survey of the discharge. Samples are analyzed for pH, BOD or COD, TSS, oil and grease, total Kjeldahl nitrogen (TKN), hydrogen sulfide, dissolved sulfide, total cyanides, or metals dependent on the industry category.
Sample collection field crews work throughout the City on a daily basis and their observations and sampling can lead to investigations into illicit or noncompliant discharges. All industrial discharges are subject to city, state, and federal regulations, and sewer rates for industrial discharge are established based on the data collected by the industrial sampling program. Illicit and noncompliant discharges increase resource recovery costs and therefore the rates of compliant dischargers. In addition to regulating industries the City provides customer support for facilities required to comply with Pretreatment Regulations. This support includes consultations with industries to discuss sampling results and the impacts on billing.
Hydrogen sulfide (H2S) is monitored at industrial locations with the potential to generate or discharge and release the gas in the sanitary sewer. Hydrogen sulfide is a potential hazard to human health and the integrity of the collection system. The gas may be dissolved in wastewater and released by agitation or other changes to the wastewater in the sanitary sewer system. Hydrogen sulfide limits of 2 mg/l for a monthly average, 3 mg/l for a 24-hour average, and 10 mg/l for an instantaneous peak are established in discharge permits for potential industrial generators.
The Sanitary Engineering Analytical Laboratory (SEAL) provides quality analytical laboratory services and scientific advisory in support of Transportation and Utilities, the Lincoln Wastewater System and other publicly-sponsored programs that protect and enhance the city of Lincoln’s water quality.
Each day, skilled field personnel from Sanitary Engineering and the water resource recovery facility collect and deliver samples from fresh waters, industrial effluents, wastewater treatment influents and effluents, and recovery facility biosolids to the laboratory. SEAL environmental scientists analyze these samples in the trace metals, Inorganic chemistry, and microbiology fields of environmental analysis, resulting in SEAL performing more than 65,000 analyses per year. The data from the analyses are validated and stored in a database containing nearly 20 years of environmental data. This information forms a database that is used to:
- Monitor trends in wastewater effluents and local waters
- Enforce industrial waste regulations
- Provide analytical data for industrial wastewater surcharge calculation
- Formulate plans and action programs to protect and enhance local water
- Monitor recycled products such as biosolids and reclaimed water
- Protect public health
- Participate in cooperative studies with other governmental and research agencies
The laboratory works with field personnel to understand project goals and assist in determining specific sampling, chemistry, toxicology and microbiology testing requirements. They aid in project planning, technical and regulatory consultation, procurement of contract laboratory or other technical services, and final report generation. During the planning process, the laboratory works with each entity to scope and schedule lab support for each project. This project information is typically coordinated in a manner which provides all involved the information necessary to know exactly what work will be done, when it will be done, and the roles and responsibilities of the project team members. Laboratory personnel monitor the analytical progress of projects to ensure timely completion, coordinate the lab’s response to project changes, and help ensure that the right type and quality of data are generated for each project. Areas of concentration are:
- Trace Metals
- Inorganic Analysis
- Microbiology
- Quality Assurance Program
- Special Liquid Waste Dump Station