Iron & Arsenic Removal Water Treatment Plant

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 dangerous 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).

Project Summary

Background

The City of Reading is located in western Hillsdale County on M-49, approximately 10 miles north of the Indiana State line. 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. The City adheres to the National Clean Water Act and the Michigan Clean Water Act, which requires testing for a variety of chemicals that may be harmful to public health, or may cause adverse cosmetic or aesthetic effects. Under the revised (2004) maximum contaminant levels (MCL) for arsenic of 10ppb, the City's water supply was in violation. J&H and the City worked closely with the MDEQ to produce a viable solution to the problem.

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 located three miles south of the City limits. The capacity of the wells is 600 gpm each for a total capacity of 1,200 gpm, and a firm capacity of 600 gpm. Prior to the project, water was fed directly from the wells into the system, and therefore only limited treatment options were applied before the water was delivered into the homes of the city residents.

Prior Water Treatment Practices

Prior to the completion of the WTP the water that the City pumped out of its wells received very minor treatment before entering the distribution system. The water was treated with a poly-phosphate blend to sequester the iron, and chlorine was added to provide a residual measure of control against microbial activity. All of the additives were previously fed directly to the water flow prior to it entering the distribution system, which allowed for control of the water near the source wells. Although this system was adequate for iron and microbial control, it did not serve to remove the arsenic in the source water.

Need for the Project

The water that flows from the City's wells is generally high in iron, and prior to the new WTP, contained levels of soluble arsenic that were frequently above the current federally mandated MCL of 10ppb. Following the change by the USEPA (compliance mandated for January 23, 2006) on the level of arsenic that is to be
considered acceptable, (from 50ppb to 10ppb) the presence of arsenic in the source water became the most current and pressing concern faced by the City's water officials. The new EPA rule that sets the arsenic MCL at 10ppb is based on the arsenic concentrations in the entire distribution system. The presence of arsenic in
drinking water can become a concern when it reaches levels over 10ppb, according to the most recent standard set by the EPA. In 2005 the City of Reading began to implement a plan that would reduce the arsenic concentrations below the 10ppb MCL.

Dangers of Arsenic

Arsenic is a semi-metallic element that is odorless and tasteless to humans. It contaminates the drinking water supplies of people throughout the world in varying degrees of contamination. It enters the drinking water supplies from natural deposits in the ground or from poor industrial or agricultural practices. Arsenic is considered to be a human carcinogen, and can cause severe health problems even in people exposed to relatively low levels, if they are exposed to it for a period of many years. The primary reason behind the strict rules regarding the MCL of arsenic is the detrimental health effects that have been strongly linked to arsenic exposure.

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. 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 additive addition. The selected treatment system was designed to remove both iron and arsenic through chemical processes. The implementation of this process provided the City with iron and arsenic removal that has now been shown to reduce the arsenic concentration below the 10ppb MCL. A vertical pressure vessel filtration system was chosen for its proven record of iron/arsenic removal and its low operational costs.

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, a heavily 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. The Plant was also designed to accommodate the future installation of high-service pumps and related control equipment. The interior of the Plant provides an ample volume of space for future expansion and individual containment rooms for each of the chemicals fed during the treatment process. 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, wells, and any future Plant or wellfield expansions that the City may undertake.

Current Situation

The alternative proposed by the Jones & Henry planning team was implemented, and following the 2007 design phase, was constructed in 2008/2009. The WTP was recently completed, brought online fully, and has been treating water for several months. 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 full compliance with the MDEQ requirements and is currently undergoing the process of implementing new operational/reporting procedures for the WTP.

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