MWRA

The MWRA is a regional wholesaler, providing water and sewer services to 61 cities and towns in metropolitan Boston. The MWRA was federally formed in the 1980s due to the Boston Harbor being considered to have the dirtiest water in America. Their goal was to protect the harbor and other greater Boston waters from pollution and sewer/weather overflows. One of the MWRA’s staple projects is the Deer Island Water Treatment Facility. This is where I interned with the Engineering Services group. 

As an Engineering Services Intern, I had the opportunity to work alongside experienced mechanical engineers, project managers, project engineers, and many more facility pipe/plumbing engineers. Throughout the course of my internship, I gained valuable insight into the world of engineering and the various roles and responsibilities within the field.

I mainly worked with mechanical engineers and project engineers who taught me about the design and implementation of mechanical systems and equipment. I was able to observe how they approached problem-solving and how they applied the principles of physics, thermo and fluid dynamics, and mathematics that I’ve only learned in a classroom to design and create solutions to complex engineering challenges. I was also able to learn about the challenges that arise during construction and how project engineers work with contractors to resolve them. It was also very interesting to observe project managers manage budgets and schedules and how they ensure that projects are completed within the specified time and cost constraints. I was also given the opportunity to review, update, and edit engineering drawings made in the AutoCAD software. I was able to see how AutoCAD is used to create detailed drawings, schematics, and 3D models, which help engineers to visualize and communicate their designs.

Overall, my internship with the Engineering Services group at MWRA provided me with a wealth of knowledge and practical experience in the field of engineering. No one ever really thinks about what happens after you flush but I’m proud to say that now I do. I am grateful for working with such talented and experienced professionals who taught me a lot about engineering I couldn’t learn in a classroom.

As a public authority and state agency, I am able to share some of the many projects I worked on while at the MWRA:

Background

After wastewater passes through primary and secondary treatment, it is disinfected with sodium hypochlorite to kill bacteria. There are 2 large disinfection basins on Deer Island that do the mixing of the hypo. For these basins, there are 2 chemical analyzers that provide data for the process variables, including total chlorine (T-CI) residual, pH, ORP, and temp. The two analyzers are the Hach CL17 and the Chemtrec HydroACT. In Chlorine Analyzing there are two main methods of detection:

The Hach is an instrument that uses a DPD Colorimetric Method; which includes a N, N-Diethyl-p- phenylenediamine (DPD) indicator and a buffer. Chlorine oxidizes DPD (indicator) to produce a red color where the intensity of the dye corresponds to the chlorine concentration. The chlorine concentration is measured photometrically by shining a specific wavelength of light through the colored sample; measuring the light absorbed.

The Chemtrec uses a Free Chlorine Amperometric Method. This is an electrochemical method that measures changes in electric current across electrodes (anode and cathode) which results from a chemical (redox) reaction taking place at the electrodes. This measurement sensor measures a reduction of chlorine at the cathode and the oxidation of the anode. The resulting electrical current is proportional to the concentration of the chlorine.

The Chemtrec system was implemented a little over a year ago to see if its method of measuring could provide an update to the Hach system. However, this was not the case so the maintenance engineers on Deer Island decided to move forward with updates to the Hach system. These updates aim to simplify its structure and make it similar to the Chemtrac system for testing and cleaning. 

My Task

I was tasked to look at Hach documentation and develop a schematic/section drawing for a sample system layout on a uni-strut frame. The specific concern here is the mechanical installation of the device. The goal will be to build a full manifold on a bench and then bolt it down and connect it in the field.  

Final Design

After various designs and considerations from the maintenance engineers, I utilized AutoCad to deliver a design for the Hach sampling system. This design uses a positive displacement hose pump to transport the hypo from the basin to the sample area. There is a cleaning suction and cleaning drain that allow for fresh water to be sucked in for maintenance before a new sample period.

Background

At the Clinton Wastewater Treatment Plant, there is a project to relocate the current sodium bisulfite system. The current system is located on the first floor of the sludge pumping/chemical building. This location, although convenient, is unsatisfactory. Seen in the images below, there is no containment area for the tank itself or the pump. This is a hazard if there was a spill or leakage. There is also only one sodium bisulfite tank with no redundancy. 

Also, since the time the plant was built, the plant no longer has a use for pure polymer as a part of its disinfection process. Now, for that process, the plant uses sodium carbonate (soda ash). So the old polymer storage containment area is no longer needed.