Features

November 2006, Vol. 18, No.11

Are You Looking Into Your Outfalls?

Knowing the condition of an outfall pipe and diffuser system assures regulatory compliance for one wastewater utility

NansemondOutfall1 Bruce W. Husselbee and Shawn M. Heselton

At most wastewater treatment plants, an outfall pipe or channel conveys treated effluent to an adjacent receiving stream or other body of water. To limit impacts to the receiving stream, utilities often install a diffuser system on the end of the outfall pipe that increases the dilution of the effluent into the ambient water.

These systems are just as important as any of the other processes at a wastewater treatment plant, but they are less visible. Therefore, it is important to pay attention to outfall design, installation, and operation. After all, it is usually obvious whether or not a clarifier is functioning properly, but since outfall diffusers are rarely inspected, their condition often is unknown.  Read full article .

 

Equipment First, Plant Design Second

When opting for small-footprint technologies, utilities should select the treatment equipment first to minimize overall project costs

DryCreekIFAS Cindy Wallis-Lage, Terry Johnson, Brad Hemken, and Baneeta Sabherwal

In response to the need for high-quality, reusable effluent and small-footprint options, several new treatment technologies — membrane bioreactors (MBRs), integrated fixed film activated sludge (IFAS) systems, and moving bed biofilm reactors (MBBRs) — are gaining popularity.

However, each technology varies greatly from vendor to vendor, so it is no longer cost-effective or appropriate for equipment selection to be part of the overall project bid.

The specialized equipment required for MBR, IFAS, MBBR, or tertiary membrane processes often is a significant percentage of a project’s total construction and operations and maintenance (O&M) costs. Satisfactory equipment performance is also critical for project success. So, owners are interested in the suppliers’ qualifications and experience, as well as some form of competitive procurement or price negotiation.   Read full article . 

 

So, You Decided To Build an MBR?

Tip to help optimize process performance

DSC02377 Rion P. Merlo, John Bratby, John Holland, Henryk Melcer, Denny Parker, and Eric Wahlberg

Membrane bioreactors (MBRs) are a viable treatment alternative when a wastewater utility has footprint constraints, a market for reclaimed water, or needs to produce a high-quality effluent. Because MBRs can handle higher mixed liquor suspended solids (MLSS) concentrations and don’t need secondary clarifiers, their footprint is much smaller than that of a conventional activated sludge process. MBRs can produce effluent with biochemical oxygen demand (BOD) and total suspended solids levels of 2 mg/L or less. They also can provide biological nutrient removal.

However, MBRs are not “off-the-shelf” units and require good process engineering to ensure cost-effective operations. Following are some issues to consider when designing an MBR plant.  Read full article . 

 

Operations Forum Features

Biosolids Dryer Safety: What Every Operator Should Know

OFdryerPhoto Ray Barrett and Joey Herndon

An increasing number of municipalities are selecting thermal drying as the solution for the growing problems associated with biosolids disposal. However, it is important to incorporate the appropriate electrical, mechanical, and process safeguards into the drying process.

Operating these drying systems requires a well-trained staff that is intimately familiar with the dryer’s operation and safety interlocks. Otherwise, potential safety hazards may beinadvertently introduced, outweighing the benefits of converting to a Class A product.  Read full article .

 

Bidding the Polymer Contract

OFBidArt Michael Zabilansky and Peter LaMontagne

Thickening and dewatering polymer is one of the largest costs for wastewater treatment plants. This article looks at one utility’s experience in negotiating a new polymer contract, when its existing one fell through. To stabilize its budget, the utility wrote a better contract, used qualification trials to choose the best product available, and looked to automation to optimize polymer dosing.  Read full article . 

 

Cost-Effective Conditioning and Dewatering

A groundwater treatment facility saves big by conditioning with polymer instead of iron and lime

OFCostArt Mohammad Abu-Orf, Jeff Lambeth, and Gerald Smart

Treating and disposing of residuals account for a significant portion of operating costs at treatment plants. Among the processes that add to these costs, conditioning and dewatering of residuals are two of the most expensive. This cost grows larger if inorganic conditioners are used instead of polymers, because they require higher dosages and the increased cake mass that results increases disposal costs.

A water treatment plant in Henderson, Nev., investigated options to improve dewatering, including pretreatment with enzymes before inorganic conditioning and before polymer conditioning, as well as polymer conditioning alone. Polymer conditioning alone appears to condition the solids properly before dewatering, even when employed at a much lower dose than is used normally.  Read full article .