The Challenge

Many municipal and private water treatment plants need to condition their incoming raw water with the removal of suspended solids materials. This task is typically performed through chemical conditioning with the addition of an approved precipitating / flocculating chemical in preparation for gravity settling of these solids.  In many water treatment plants, aluminum hydroxide (Al(OH)2) precipitates forming a “sweepfloc” that tends to capture suspended solids as it settles out of suspension forming an Alum sludge.  Wet Alum sludge makes up to 5% in percent solids and is typically difficult and expensive to treat.

Following the initial sedimentation of solids, the pre-treated water is then typically sent to mixed media sand/gravel filters for a final polishing step prior to disinfection (i.e., chlorine addition) then pumped to reservoirs/storage tanks for consumer distribution. 

The sand/gravel media filters at the Town of Braintree, MA Water Treatment Plant were fouling with solids much more frequently than normal requiring higher backwash cycles due to carryover of sludge from their Alum Sedimentation Pond No. 2.

The Braintree Water Treatment plant manager investigated several methods of removing Alum sludge from the basins and found large cost variables among pumping, dewatering and disposal methods.  Braintree Townships’ consultant reviewed mechanical (i.e., belt filter press, plate & frame filter press) and concluded for their application that Geotube® engineered geotextile bags for dewatering and disposal of sludge on a bone-dry-weight basis was most cost-effective.

The Braintree Township engineer designed a level lay-down area based upon UMPS’ estimate for the size of Geotube® containers needed for one year’s estimated volume of alum sludge wasting from their sedimentation basins.  The lay-down pad’s design elevation allowed for the collection of clear filtrate from the 120-foot circumference by 90-foot long Geotube® which was pumped back to the headworks of the settling basins as shown in the photos below.  The maximum dewatered sludge capacity of the 120-foot circumference by 90-foot long Geotube® is approximately 1,300 cubic yards.

The Outcome

Time & Patience

From the 2020 Alum sludge Geotube® dewatering that UMPS performed for the Braintree Water Treatment Plant, since the location of the filled Geotube was not affecting plant operations,  the benefits of “time and patience” had a dramatic effect on the conditioning of the dewatered Alum sludge.  By permitting the Geotube® solids to thoroughly slack dry and go through two “freeze/thaw” winter cycles, this dramatically decreased the % moisture, maximizing solids content to 86.7% and decreased the off-site disposal costs as shown in the photo.

“The folks at UMPS are confident, reliable, and enthusiastic to adjust to our needs. Being a certified Geotube® installer using proven Smartfeed® Technology for accurate chemical addition in real time resulted in water quality ≤ twelve total suspended solids and dryer solids filter cake than previous contractors.” – Lou Dutton Water Plant Director.

As the largest inland commercial diving services company in the United States, Underwater Construction Corporation and Underwater Mineral Processing Services has a staff of over 200 divers, supervisors and project managers operate from multiple regional locations in Maine, Connecticut, Maryland, Michigan, Tennessee, Wisconsin, Texas, South Carolina and the United Kingdom. Through our global network of offices and associates, UCC has performed projects in over 25 countries. 

Contact Jim Meagher at 207.741.2955 / jmmps@maine.rr.com for any of your pit, pond or lagoon sludge/sediment dredging and dewatering services.

In the shadow of the Rocky statue at the Philadelphia Museum of Art, Underwater Mineral Processing Services (UMPS), an operational division of Underwater Construction Corporation (UCC), was contracted under a Philadelphia Water Works Park Amenities & Island Enhancement Project to process 2,000 gallons per minute (gpm) of hydraulically dredged sediment from the interconnecting channel of historic Boathouse Row to the Schuylkill River in Philadelphia, PA.

The challenge was the installation of the dewatering equipment in an area only 60 feet by 60 feet.  But just like Rocky – UMPS prevailed!

An eight-inch diameter Ellicott Mud Cat cutterhead dredge conveyed high content mud, debris and sediment to a primary vibratory scalping screen for separation of all material over two inches.  The two-inch by zero fraction is directed to a 36-inch diameter dewatering screw auger washer that liberated fine sediment fractions, which were directed to a 1,500-gpm cluster of 16 – four-inch diameter hydrocyclones.

The underflow reported to a high frequency vibratory dewatering screen cutting at 45 microns.  The screw auger washer discharged two-inch by three-eighths of an inch fractions as a stackable material for subsequent slack-drying and load-out for off-site transportation and disposal.  

The 45-micron by zero dredge water was processed through a UMPS SmartFeed unit that continuously monitored flow rate and solids content. 

Pre-mobilization bench-scale testing upon representative samples focused upon extensive jar-testing for the identification and optimization of coagulant and polymer chemistries for enhanced fine solids sedimentation and separation.  With the UMPS’ SmartFeed continuously monitoring the incoming dredge slurry flowrate and percent solids concentration, the identified chemicals were automatically injected inline and mixed before being delivered to the UMPS 2,000 GPM High-Rate Clarifier/Paste Thickener.  

The UMPS’ SmartFeed chemical additions were updated every seven seconds in response to variations in flowrate and solids concentrations.

A positive displace pump conveyed approximately 38 percent solids underflow from the UMPS High-Rate Clarifier/Paste Thickener to a Decanting Centrifuge that also produced a stackable material for subsequent slack-drying and load-out for off-site transportation and disposal. 

A total of 1,500 cubic yards of sediment was successfully dredged, dewatered and transported off site for disposal with the Boathouse Row water channel flow to the Schuylkill River being fully restored. 

Contact Jim Meagher at 207.741.2955 or jmmps@maine.rr.com for bench-scale testing and provision of turnkey hydraulically dredged material dewatering from your waterway areas, pits, ponds and lagoons.

The Challenge 

Cooling water intake cleaning is a continual challenge for power plants. But what happens when the cooling water intakes are screened laterals that are the heart of a Ranney Radial Well System?  

The Kleen Energy power plant in Connecticut has two Ranney Vertical Wells supplying their cooling water, which have been in continual use for over 10 years. The plant began to experience growing inefficiencies with their Ranney Well No. 1 critical cooling water intake structure, with deterioration of water clarity. The plant’s raw water, green sand filters were rapidly overloading with sediment, reducing flows, creating significant maintenance issues and operational constraints.

Kleen Energy hired Underwater Mineral Processing Services (UMPS), a division of Underwater Construction Corporation (UCC), to assess the causes of this inefficiency and develop a turnkey solution for the rehabilitation of the Ranney Collector Well screened laterals.

The Project

UMPS and UCC employed their extensive experience in power plant diving and water intake maintenance services, along with a portable process for water analysis and treatment systems, to rapidly assess the root cause of the reduced flow volume from within the blinded laterals. 

UPMS’s SmartFeed chemical conditioning mobile unit was deployed to continually monitor flow rate and turbidity through each of the radial laterals of the Ranney Collector Well. This information was used to identify underperforming laterals, inform Kleen Energy’s power plant operation team and enable them to determine remediation strategies. The accrued data on the transmissivity of the tested laterals permitted UMPS to develop a phased approach for rehabilitation of flow and water quality in the affected screened laterals.

The first phase was a thorough diver inspection of water pumps and vertical well structure elements.  UCC developed a comprehensive site safety plan for the confined diver operations within the deep well caisson.  UMPS provided Kleen Energy with a detailed underwater video record of the Ranney Well infrastructure’s operational condition and integrity.

The second phase was inspection by diver-deployed, remotely operated video camera crawler unit into each of the 12-inch diameter screened lateral pipe. The reconnaissance data accurately determined the overall length of the screen pipes. It also identified mechanical deficiencies in the screen pipes, such as collapsed screen sections, screen weld seam breaks, sediment intrusion, and mineral depositional fouling.

The third phase focused on the identification and quantification of each radial lateral deficiency for hydraulic flow and sediment and turbidity contribution.  Using Supervisory Control and Data Acquisition (SCADA) collection, analysis and information management, flow and turbidity were accurately graphed during each controlled hydraulic demand test of each screen pipe lateral.

The Outcome

UMPS/UCC developed and implemented a phased technical approach defining and quantifying the factors contributing to decreased flow rates and deteriorated water quality of the Ranney Collector Well.  

The customer was provided detailed documentation identifying which of their Ranney Well laterals were underperforming in flow transmission and/or contributing to excessive sediment turbidity.  These conclusions permitted the client the opportunity to isolate a poorly performing screened lateral, until a rehabilitation/restoration task could be initiated.

The results of the SmartFeed System’s Flow Rate / Total Suspended Solids test on five of the Kleen Energy Ranney Well laterals are presented in the Data Collection Ledger below.

The following observations were drawn from the data set:

• Six remaining laterals after flushing showed a substantial decrease in total suspended solids.
• Laterals’ hydraulic capacity will significantly increase after water jetting of the mineral deposit build-up at the screen pipe interface. 
• Vertical well static level testing showed a pump rate of 977 gallons/minute of the combined six laterals is the inflection point of well recovery rate.  
• The bottom of the well has an estimated 6 inches of accumulated sediment or 6.9 cubic yards
• Laterals 1A and 2B contribute the highest solids loading. UMPS recommended isolation of these laterals after testing.

Jeff Erksa, Kleen Energy’s Maintenance Supervisor, completed a well operation review several months after phases one and two. He stated, “The well performance was within plant parameters, and the phased approach of the UMPS/UCC team was instrumental in a safe and cost-effective analysis of the Ranney Well rehabilitation.”

Once Kleen Energy completed these reviews, it could decide to either continue with the current deteriorated operational parameters or move to Phase Four: Remove sediment and mineral deposits using high-pressure / high-volume jetting, surgical filtration of liberated screen debris, and real-time confirmation of restored screened lateral flow.

As the largest inland commercial diving services company in the United States, Underwater Construction Corporation and Underwater Mineral Processing Services has a staff of over 200 divers, supervisors and project managers operate from multiple regional locations in Connecticut, Maine, Maryland, Michigan, South Carolina, Tennessee, Texas, Wisconsin and the United Kingdom. Through our global network of offices and associates, UCC has performed projects in over 25 countries. 

Contact Jim Meagher at 207.741.2955 / jmmps@maine.rr.com for any of your Ranney Well radial lateral flow/condition assessment and restoration needs.