Efficient Wastewater Treatment: Old and New Working Together

When it comes to waste­water treatment and processing, there are three challenges for operating plants, says Paul Rice, director of marketing for the Municipal Products and Services Division of Evoqua Water Technologies. One is getting more processing and capacity out of existing equipment, much of which is aging and requires retrofitting, rehabilitation, or upgrades.

New nutrient requirements present another challenge. “Those vary from state to state, whether it be nitrogen or phosphorus,” says Rice. “Wastewater plant operations have new limits that their permits are going to have to hit.” A third challenge: working to decrease operational-related energy costs.

While there are a number of new technologies on the market to meet the challenges, there are “tried and true technologies” which have been taken for granted that are “well-proven and well-demonstrated” and can be added into secondary clarifiers to improve operations, says Rice.

When it comes to waste­water treatment and processing, there are three challenges for operating plants, says Paul Rice, director of marketing for the Municipal Products and Services Division of Evoqua Water Technologies. One is getting more processing and capacity out of existing equipment, much of which is aging and requires retrofitting, rehabilitation, or upgrades. New nutrient requirements present another challenge. “Those vary from state to state, whether it be nitrogen or phosphorus,” says Rice. “Wastewater plant operations have new limits that their permits are going to have to hit.” A third challenge: working to decrease operational-related energy costs. While there are a number of new technologies on the market to meet the challenges, there are “tried and true technologies” which have been taken for granted that are “well-proven and well-demonstrated” and can be added into secondary clarifiers to improve operations, says Rice. [text_ad] Most of today’s secondary clarifiers were constructed 40–50 years ago and a lot of them have riser pipe in them, says Rice. For those facilities, the riser pipe clarifier can be converted to use a Tow-Bro hydraulic sludge removal device to help remove settled solids within 30–40 minutes uniformly over the entire basin floor area without re-suspension of the solids, ensuring complete and positive control of the sludge blanket. “It helps to handle higher concentrations of return activated sludge,” notes Rice, adding that it improves efficiency in an operation challenged with sufficient capacity. Additionally, “there are a fair amount of clarifiers that have energy-dissipating inlets to slow down inlet water since any kind of currents mean that solids stay suspended longer,” says Rice. “The longer solids are suspended, the slower the process goes and the more space that is required for clarification.” Evoqua Water Technologies has a Flocculating Energy Dissipating Well Arrangement (FEDWA) baffle system designed to help the flocculation efficiency of an operation. It is a relatively easy upgrade to a circular clarifier. As with the other way around, new technologies can augment the benefits of existing ones, says Rice. Evoqua Water Technologies’ BioMag Ballasted Biological Treatment System helps flocculent settle faster through the infusion of magnetite as a weighting agent that attaches to the flocculent, says Rice. “The advantage of BioMag is it’s a system you can apply to the biological process at secondary clarifiers, allowing you to get much more treatment capacity in the same footprint,” he adds. “You can even free up tanks for other functions or do more processing in the same tank by applying this ballasted technology.” BioMag is designed to double or triple biological treatment capacity and achieve enhanced nutrient removal limits within existing tanks. It is designed to routinely deliver total nitrogen less than 3.0 milligrams per liter, total phosphorous (TP) less than 0.2 milligrams per liter, and turbidity less than 1 NTU. “It’s a drop-in to the plant, so you’re not requiring a new footprint for anything,” says Rice. “You’re just adding this ability to do ballasted settling into the secondary treatment, which meets the need to do more with less. It can help the existing process make better nutrient numbers, accommodate more flow, and add capacity to an existing plant or free up tanks for other uses.” [text_ad use_post='27751'] The CoMag particulate removal system is another magnetite ballasted clarification, but it’s used in primary clarifiers, tertiary treatment, and combined sewer overflows and stormwater management, says Rice. It performs similarly to other ballasted systems that use sand as a ballast instead of denser magnetite. CoMag is designed to produce effluent nearly equivalent to ultra-filtration at capital and operating costs competitive with conventional alternatives. It also is NSF-approved for drinking water applications. The CoMag particulate removal system is designed to deliver TP less than 0.05 grams per liter, total suspended solids less than 2.0 grams per liter, and turbidity less than 1 NTU. “In primary systems, it can help give you up to 10 times more capacity and it can help handle upsets and storm flow,” says Rice. “Many people are trying to figure out how they are going to get more water through their plant. A ballasted system at the front end of the plant can be a big help for that. On the back end of the plant, you can use this ballasted technology for nutrient removal.”