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Wastewater Division

Wastewater Plant Update

Posted: September 5, 2008

Update September 2008: (Click on thumbnails to view pictures larger)

Emergency Generator/Engine. In order for the City to ensure continuous protection of public health and the environment, the wastewater treatment plant needs to function even in the event of an electric power failure. To accomplish this, a onsite diesel powered engine-generator will power all the necessary plant equipment. The 5,000 gallon diesel fuel storage tank arrived first and was set on its concrete equipment pad. The engine-generator arrived a week later. After the delivery truck positioned it near its final resting spot, 2 cranes were used to fly the 40,000 pound load to sit on top of the fuel storage tank. It will be hooked up to the plant’s electrical system and an automatic transfer switch will start the engine to generate the required power for the plant if utility electricity is lost.

Electrical System. September continued to be a very busy one for Smith Electric, the electric subcontractor. Wire and cable were continued to be pulled throughout the site. Once the wiring is laid to the electric switchgear, it runs to the motor control centers (MCCs) and then out to the individual pieces of equipment. Other equipment such as this transformer for the Filter/UV equipment were also installed. This work will be on going for the foreseeable future.

Influent Pump Station (IPS). This new pump station will contain 4 non-clog, vertical column-type pumps to pump the wastewater after it arrives at the treatment plant to the downstream treatment units. These pumps were delivered to the site and await installation. They are in the picture laying horizontally, but will be rotated up 90 degrees to be lowered into the pump station. The IPS top slab and pump pads were poured and the electric disconnects for the pumps installed.

Grit Handling. As Parsons, the prime contractor, will be checking the automatic controls and other equipment in this treatment unit in October, there was much activity to get everything ready. Piping for grit removal, agitation air and water was installed in each of the 3 grit hoppers. Once the grit material is removed from the grit hoppers, it’ll be pumped to washing and dewatering equipment. That equipment was previously installed, but the framework for the access walkways and stairs was installed this month.

Oxidation Ditches (ODs). The 4 air blowers which will deliver air to the ODs had some of their air piping installed in the blower building. This air will be sent through fine bubble diffusers arranged in the bottom of the ODs to introduce dissolved oxygen to the wastewater. Installation of the diffuser brackets was begun.

Once the wastewater has been treated in the ODs, it’ll pass through pipes to the secondary clarifiers. The installation of this piping was completed. This piping is of large diameter (36 inch), as seen by the size of its fittings.

Secondary Clarifiers. Since most of the equipment has been installed in these tanks, it was time to install the grout topping on the floors. This is a final, smooth finish layer to the floor of each tank. The next step was to install rubber scrappers at the bottom of the sludge collector arms. These scrappers will help keep the heavier sludge material liquid enough to be sucked out of the tanks by the Return Activated Sludge (RAS) pumps. These pumps were installed 2 pumps per tank for a total of 6 pumps. These pumps are similar to the IPS pumps and once installed are seen in this picture with only the top part showing; the rest of the pump is below grade. Work continued to install connecting piping to these pumps.

Solids Handling. Most of the sludge removed from the secondary clarifiers will be returned to the ODs by the RAS pumps, but some will be sent to the new Dissolved Air Floatation Thickeners (DAFTs). Internal piping and other equipment was installed in these 2 circular tanks. Once sludge is thickened here, it is pumped to the anaerobic digesters for additional treatment.

In addition to sludge, grease from restaurant grease traps will be pumped to the DAFTs. It’s important to keep this grease out of the sewer pipes that carry the wastewater to the treatment plant (it can plug up the pipes), so it’ll be trucked to and dumped into this new grease station before going to the DAFTs.

Sludge Lagoons. Shaping and contouring work on the second lagoon continued through September in preparation for the installation of the heavy duty plastic liner. The first lagoon has already been lined and has been placed in service.

Filter/UV building. Rebar and forms for the walls of the Secondary Effluent Equalization Pump Station (SEEPS) were installed and the first lift of the concrete walls were poured. Water from this pump station will be pumped to the Filter/Ultraviolet disinfection building. Large diameter piping to and from the filters was installed. Once the fine suspended materials are removed from the water passing through the filters, it’s ready for disinfection. The water will travel through 2 parallel channels which contain 11 UV lamp modules per channel, each module contains 40 lamps. These modules were dry fit into the channels.

Construction Management. Throughout the fabrication and installation of equipment and materials, the construction management inspectors from Brown and Caldwell complete and document their thorough inspections. One such inspection required a confined space entry into a 45 foot deep pump station. The inspector came out of the hole unscathed and the equipment passed inspection.

Check back again in November to see what happened in October.