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New Dewatering Device Provides Economical Flexibilty | Iron/Arsenic Removal Water Treatment Plant, Reading, Michigan | Green Building Ramblings
New Dewatering Device Provides Economical Flexibility
BY DANIEL W. MILLER, P.E.
Biosolids land application costs continue to rise and the time window to land apply biosolids is shrinking with newly proposed regulations prohibit that spreading on frozen ground. As a result many communities will look to increase their biosolids disposal flexibility and options. The Village of North Baltimore, Ohio was in such a position.
The Village had “as-needed” arrangements with a private biosolids application firm to land apply their anaerobically digested liquid sludge. While their liquid solid storage tank (200,000 gallons) could provide approximately 120 days of storage, the Village still experienced difficulty managing solids between land application periods. Additionally, the Village had also experienced elevated zinc levels in their sludge which could prevent land application of the biosolids.
Jones & Henry performed a study and determined that the Village’s disposal flexibility could easily be improved by adding solids dewatering to permit landfilling of their solids in addition to land application.
The drawback to landfilling is that the costs are typically greater than liquid land application. Land filling can be competitive and even economical if the cake solids can be produced economically, with a high solids content. Also with landfilling, the nutrients contained in biosolids are not recycled.
Traditional dewatering alternatives have been either a belt filter press or a centrifuge. New devices recently on the market include a rotary fan press, screw press and the volute dewatering press.
While new to the US market, the volute dewatering press was developed in Japan 25 years ago and has over 850 installations worldwide. This track record and the device’s claims of high cake solids, minimal operator attention, lower energy consumption and reduced washwater usage, caught the attention of the plant’s superintendent, Andy Patterson.
The Village and Jones & Henry made a visit to a new installation in Oscoda, Michigan and had a pilot study conducted at the plant by PW Tech. The pilot study was successful and the project moved ahead.
A volute dewatering press is similar to a traditional screw press; however it utilizes a unique “dewatering drum”. The drum has a series of fixed and moving rings. The slow constant movement of the rings developed by the internal screw, cuts into the sludge to expose wetted surfaces and allow the passage of filtrate without clogging. As the pitch of the screw narrows and the gaps between the fixed and moving rings decrease, the sludge dewatering increases.
Volute dewatering presses are sized based on dry pounds per hour, and an 850 dry pound/hour unit was selected for North Baltimore the next to largest unit made. Based on their 107 dry tons of solids generated each year, the device would require approximately 250 hours of operation, or less than one day per week.
North Baltimore’s installation also included enclosed storage for their disposal container (to minimize odors and vector attraction) as well as space for vehicle storage adjacent to the dewatering equipment.
As with most dewatering devices, a feed pump, grinder, and polymer feed equipment were installed at the new dewatering facility.
The results have been terrific.
The press typically achieves 30-35% solids utilizing 20-30 pounds of polymer per dry ton. The unit requires minimal operator attention during operation, is very quiet, and utilizes only 20 total connected horsepower during operation including all pumps, grinder, and discharge screws.
Disposal costs including landfill disposal, power, and polymer will be approximately $17,300 per year. This equates to approximately $0.031 per gallon. Their current liquid land application program was costing $0.035 per gallon.
The key is flexibility! Biosolids can now be removed from the plant at anytime, reducing concerns with land application timing limitations, and biosolids which do not comply with the biosolids regulations. Recently, the plant experienced plugging in its discharge line from the anaerobic digester. In order to unplug it, the entire contents of the digester was transferred to the storage tank. This sludge was not completely digested and could not be land applied. With the new volute dewatering press, the Village pressed the material and delivered it to the landfill at minimal cost.
The entire project’s construction cost was approximately $780,000.
Iron/Arsenic Removal Water Treatment Plant, Reading, Michigan
BY PAUL ROMANO, P.E. & JOHN BAYHA
Jones & Henry recently completed the design and construction administration of a new 0.25 mgd water treatment plant (WTP) designed to remove iron and arsenic from the City of Reading’s drinking water supply. Jones & Henry and the City have been working together for several years to implement a treatment system to remove the metal arsenic from the City’s drinking water. Throughout this process J&H has been in close contact with the Michigan Department of Environmental Quality (MDEQ) which has been functioning in an oversight capacity for the project. J&H also assisted the City in obtaining the project’s funding from United States Department of Agriculture-Rural Development (USDA-RD) and Community Development Block Grant (CDBG) sources (final construction cost $1.65 million).
Background
The City of Reading is located in western Hillsdale County. The City has a population of approximately 1,086 (2007) that has remained relatively stable in recent times. The City’s water system was originally built in the early 1900’s, and since that time it has been upgraded on several occasions.
With the revised (2004) maximum contaminant levels (MCL) for arsenic of 10ppb (Drinking Water Standard), the City’s water supply was in violation.
Funding Assistance
Given the substantial cost of a new iron/arsenic removal WTP, the City requested assistance from J&H in securing project funding through various government programs. Through the USDA-RD Program the City was able to secure a $1.15M low interest loan as well as a grant for $0.35M.
Due to the City’s challenging economic conditions with a certain percentage of the population qualifying as low-to-moderate income (i.e. LMI), an additional $0.50M grant was awarded from the Michigan Economic Development Corporation through the CDBG program.
Existing Water System
The existing Reading water distribution system is fed by two wells, each with a capacity of 600 gpm. The water was treated with a poly-phosphate blend to sequester the iron, and chlorine was added to control against microbial activity.
Proposed Project Alternative
Following a review of possible treatment options for the City’s well water, J&H designed a central water treatment facility that would remove the arsenic from the City’s water to a level below the MCL and remove iron. Included in the design was a building or “plant” to house the necessary equipment for the treatment processes and provide a secure location for laboratory testing and chemical addition.
A vertical pressure vessel filtration system was chosen for its proven record of iron/arsenic removal and its low operational costs. The filtration system was supplied by Layne Christensen Company, who worked diligently with the Owner, Contractor and Jones & Henry throughout the construction and startup phases of the project.
Construction of the WTP
Construction of the new WTP began in early 2008, and was completed in early 2009. The building that houses the treatment equipment was constructed for the long-term with concrete masonry block walls, reinforced concrete slab floor, and a roof deck of pre-cast concrete panels. The WTP is located at the site of the City’s wells and was designed to be relatively nondescript to fit with the existing conditions of the site.
The building was also sized for the future with provisions made during the construction process to allow for the installation of additional filter trains for increased capacity and future installation of high-service pumps and related control equipment.
A laboratory/office was also included in the building as well as storage and restroom amenities.
The project also included improvements to the existing well houses including: new piping and flow meters, a variable frequency drive on one of the pumps, and new controls and monitoring equipment.
The entire site is now served by a new 280 kW diesel generator that is capable of powering the WTP and wells.
Current Situation
Recent tests of the finished water from the WTP have indicated an arsenic level that is virtually non-detectable (±0.3 ppb), and it is anticipated that this will be reduced further following a “break-in” period for the filters after which the Plant’s filtration equipment will reach an equilibrium state.
The City of Reading is now in compliance with the MDEQ requirements for arsenic and is currently undergoing the process of implementing new operational/reporting procedures for the WTP.
Green Building Ramblings
BY JEFF HERSHA
So,…when is green, GREEN?
What is Green Building and how does it affect your community?
The Green movement has its’ proverbial roots in the cultural revolution of the 1960’s. Americans saw rivers ablaze, chemical waste leaching from the ground, and waterways turned to sewers. Smog was settling permanently into the LA Basin and agricultural run-off was creating a chemical dead zone in the Gulf of Mexico. Many cities and towns were discovering the byproducts of Civic and Corporate abuse and neglect of the environment.
As the impact of our growing industrial and consumer lifestyle became apparent the country moved to make amends. The formation of the United States Environmental Protection Agency,(USEPA), and the passing of the Clean Air and Clean Water Acts were center stage at the national level. State agencies such as our Indiana Department of Environmental Management,(IDEM), were formed to regulate at a state level, and grassroots organizations in our neighborhoods began picking up garbage and trash from our rivers and roadways. Recycling programs took off. We had made some terrible messes…and now we were cleaning them up.
As the awareness of our environment grew, we started thinking about the buildings in which we live and work. We looked at how the built environment impacted our natural environment. A new generation of architects, engineers, planners and builders began looking at better ways to build. We looked at the environmental impact of how and why we build, as well as the energy and environmental impacts of constructing, powering, and then ultimately razing our structures. We now look more critically at the life cycle impact of a building. The concept of “cradle to grave costs” entered the lexicon.
Leading the way today, is the U.S. Green Building Council, (USGBC) a “non-profit organization committed to expanding sustainable building practices.” The USGBC uses the Leadership in Energy and Environmental Design (LEED) Green Building Rating System to quantify and score a building’s “Greenness”. As the reigning organization of green building principals in residential, commercial, and municipal building projects, a USGBC LEED certification carries clout.
We have all seen the radio and TV commercials, as well as print advertising touting the latest in “Green”. My beautiful wife informed me one evening that our quick Thursday night dinner before soccer and Cub Scouts was “processed by an environmentally responsible food manufacturer”, and, “was produced in the world’s first LEED Certified frozen food manufacturing plant”. Wow! I had never felt better about stir-fry.
So what does this all mean to you? You are the leaders of your communities. As you look at your next fire station, wastewater plant, or administrative office building, what does this new “GREEN” mean? I can say, without reservation, “It Depends”.
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