Outage wash wastewater treatment requirements achieved after upgrade
Problem
A Midwest electric utility had difficulty meeting effluent standards at one of its coal-fired power plants. After closing its coal combustion residual ponds, the utility needed an economical way to treat boiler, precipitator and air preheater wash water. After several pilot attempts by various vendors, the NPDES permit requirements for TSS, pH and heavy metals were not being met.
Solution
United Conveyor designed, installed and operated an outage wash pilot test for nonchemical water cleaning of air heaters on two units and a precipitator on one unit. The company used an existing remote submerged flight conveyor, clarifier and chemical injection skids along with temporary equipment, including additional injection skids, a clarifier/thickener, sludge tanks and a belt press.
Result:
The pilot test was a success; the system was installed within two weeks and operated 24 hours a day for seven days. Samples of untreated and treated water were taken to monitor the solids removal efficiency and ensure that effluent limits were met. The temporary system proved that the existing bottom ash dewatering system could be used to treat outage wash wastewater. Due to the successful test, the plant will make permanent modifications to the bottom ash dewatering system to accommodate outage wash wastewater treatment. 847-473-5900; www.unitedconveyor.com
Digester helps eliminate FOG, corrosion, odor, matting and insect infestation
Problem
For 15 years, a West Coast university had battled FOG, corrosion, odor, matting and insect infestation in all 29 lift stations. Twenty-four were in the basements of buildings, and the others were located around the campus. Chemicals were ruled out due to hazards, cost and storage requirements.
Solution
After testing five products for two weeks, the university chose the DO2E Wastewater Treatment Little John Digester. Within the first hour, the unit had eliminated all issues, including the insect infestation.
Result:
After 12 months, none of the issues had reoccurred. 850-698-6805; www.do2e.com
Biotrickling filter helps city get odor issues under control
Problem
The City of Saline, Michigan, needed a system to control hydrogen sulfide gas emissions from its wastewater treatment process as odor complaints mounted.
Solution
ECS Environmental Solutions installed a BioPac-VTS bioscrubber system, including a fan with acoustical enclosure and thermostat-controlled ventilation, insulated bioscrubber vessel, and interconnecting ductwork. A radial, activated carbon odor control system was used to treat odorous air from rotating biological contactors. It included an insulated carbon adsorber vessel with two independent internal support columns to allow dual media utilization in the future.
Result:
The solution removed 99.4% of the hydrogen sulfide and 94% of all organic sulfides from the wastewater process. The system reduced gas emissions and odors and met the city’s regulatory goal for air pollution control safety. “We appreciated the prompt response and the company going above and beyond in standing by its product,” says Steve Wyzgoski, water and wastewater superintendent. 254-933-2270; www.ecs-env.com
Venturi system enables city to meet dissolved oxygen requirements
Problem
The LeSourdsville (Ohio) Wastewater Treatment Plant must meet dissolved oxygen levels at the outfall. During normal operations, oxygen is added in a cascade basin, but during storms, the river can rise to levels that flood the basin, rendering it useless.
Solution
Due to confined space in the cascade basin and limited access to the site, the city chose the Mazzei Injector venturi wastewater aeration system, eliminating blowers/diffusers and their accompanying footprint and maintenance. The modular drop-in design includes a vertical turbine pump to recirculate wastewater through a Mazzei 12050 venturi injector, which mixes air in. The resulting mixture returns to the basin through a Mazzei MTM nozzle manifold, increasing oxygen transfer and basin mixing from the bottom up. This system was designed to raise dissolved oxygen at the outfall from 3.5 to 5.6 mg/L under storm flows up to 26 mgd.
Result:
Soon after the system was installed, a storm caused the river to rise and flood the cascade basin. The post-aeration system maintained the outfall dissolved oxygen level above 5.6 mg/L at flows up to 31 mgd — 20% higher than the aeration system’s peak design flow. The quiet, efficient and reliable aeration system maintained the outfall oxygen requirement and continues to do so. 661-363-6500; www.mazzei.net
Updated receiving station increases plant’s efficiency
Problem
The Metropolitan St. Louis Sewer District Bissell Point Wastewater Treatment Plant had Schwing Bioset piston pumps and a live-bottom receiving station. The pumps, in service since 1993, conveyed biosolids cake at 25% solids to multiple hearth incinerators. The city sought a new receiving station using push-floor technology to allow dewatered biosolids to be received from other district facilities for incineration.
Solution
Schwing Bioset and Donohue & Associates designed and provided the receiving station. Push-floor technology was chosen over the live bottom for efficiency, low maintenance and improved material flow. A new piston pump and piping system transport solids into the facility. The push-floor bunker design consists of two hydraulically driven push frames that reciprocate along the bunker floor. The frames’ action breaks material bridging and feeds solids to an extraction conveyor. Rectangular bunkers allow multiple trucks to unload simultaneously. The bin includes a retractable bi-fold cover integral to the system. When not receiving biosolids, this helps contain odors and excludes rain, snow and tramp materials.
Result:
The station began operating in July 2020 and has met the district’s objectives. 715-247-3433; www.schwingbioset.com
Clarification system helps city meet phosphorus limit
Problem
The 10.85 mgd Bristol (Connecticut) Water Pollution Control Facility discharges to the Pequabuck River. The state Department of Energy and Environmental Protection issued a nutrient management strategy for freshwater nontidal streams focusing on seasonal phosphorus limits of 0.1 mg/L. To achieve this limit, the city chose ballasted clarification.
Solution
The city chose the ACTIFLO high-rate ballasted clarification process from Veolia Water Technologies (dba Kruger), proven to effectively treat secondary effluent to reduce TSS and remove phosphorus to the required level. The system delivered the smallest footprint and lowest net present value over 20 years of operation. The compact system combines coagulation, flocculation and sedimentation using microsand as a seed for floc formation. The microsand enhances flocculation and acts as ballast to enable rapid settling.
Result:
The ACTIFLO process achieves a seasonal average effluent total phosphorus of 0.06 mg/L, 40% lower than the permit level, helping improve the quality of the Pequabuck River. The system will meet evolving permit standards for years to come. 800-337-0777; www.veoliawatertech.com
