Turning Lake Conroe Water into Drinking Water

Good morning! Good afternoon! Good day students. I’m Professor Herbert Henry Oliver. But my students call me Dr. H2O. That is probably most peculiar to you all since H2O is the chemical formula for water. Why would a Professor wish to be referred to as an oxygen hydride consisting of an oxygen atom that is covalently bonded to two hydrogen atoms? Well I will tell you why…because this transparent fluid (aka water) composed of hydrogen and oxygen, is essential for life. Water is in nearly everything. It forms the world’s streams, lakes, oceans, rivers, and is essential to survival.

If you have not visited my colleague Wells, and viewed his scholarly narrative,  Where Does the Water Come From? , you simply must. Wells briefly mentions Lake Conroe, a surface water supply reservoir in Montgomery County, and how the San Jacinto River Authority’s (SJRA) Groundwater Reduction Plan (GRP) Division treats and delivers water to customers. Today, I will go in great detail to explain what must be done to this essential resource prior to consumption. Let’s get started class.

The Groundwater Reduction Plan (GRP) Story

Rapid population growth and the resulting increase in water demand has overwhelmed our county’s groundwater supply causing problems with local water wells and subsidence (sinking) of the land surface. Montgomery County’s groundwater problem didn’t develop overnight, and neither did the proposed solutions. Many have been involved in studying the problem and developing solutions. In order to protect groundwater supplies and ensure availability of other water sources, the SJRA took on the task of implementing a cost-effective and reliable solution for decreasing groundwater withdrawals. With this commitment, the GRP truly became a countywide, collaborative solution to the groundwater problem.

To ensure an adequate supply of lake water to supplement groundwater from wells, the SJRA completed a contract with the City of Houston in 2009 to purchase the right to use the City’s 2/3 share of the water supplies in Lake Conroe. The SJRA’s history of water supply acquisitions has made it possible for Montgomery County to have reliable, cost-effective water supplies to meet its future water needs.

History of Lake Conroe - Know Your Watershed

Surface Water Plant Overview

Now that we have a source of water, a treatment process must take place. Class, follow the process in the graphic below.

Raw Water Intake and Pump Station

The Raw Water Intake and Pump Station is where the water treatment process begins.

Class, I would like to draw your attention to the image to the right. The image is a photograph of the Lake Conroe Raw Water Intake and Pump Station, Step A. Here raw water is pumped from one of three depths (15’, 25’, and 42’ feet) in the water supply reservoir.

A noteworthy fact, the Lake Conroe reservoir is operated and maintained by the  SJRA Lake Conroe Division.  You simply must visit their website to learn more about the Lake Conroe Division.

Pretreatment Facility

After being pumped from Lake Conroe, the water travels to the Pretreatment Facility, at Step B, that houses three processes in one (coagulation, flocculation, and settling). Now that is what I would call the ultimate triple threat, wouldn’t you class?

At the Pretreatment Facility, chemicals are added to the water and quickly shaken. This initiates the coagulation process, where smaller, lightweight, particles stick together and create larger, heavier, particles.

These larger particles then begin to bind together and create even larger, heavier particles (the flocculation process). Gravity causes these particles to sink to the bottom of the settling basins. These particles will later be moved to the Solids Handling Facilities.

Membrane Building

Following the pretreatment process is the membrane filtration process, Step C. The Membrane Building houses the membrane filters, laboratory facilities for testing, and the Supervisory Control and Data Acquisition (SCADA) monitoring control station.

The membrane filters remove various microscopic particles, including bacteria and small particles remaining from the pretreatment process.

 

As water is pushed through the membrane filters, tiny particles and bacteria become trapped on the outside wall of the fibers.

The microfiltration membrane filters can trap particles as small as 0.1 µm (micron) in size. For reference, a human hair is about 50 µm.

The membrane filters are thoroughly cleaned by backwashing. The backwashing process reverses the flow of water backwards through the filters, dislodging the tiny particles and bacteria. The recovered water is then sent to the Backwash Equalization Basin for additional processing.

The laboratory at the Membrane Building is used to perform various tests such as temperature, pH, chlorine, turbidity, and Total Trihalomethanes (TTHM) to monitor the water treatment process.

The SCADA system allows operators to monitor and control the water plant and transmission system from a single station. Class-picture someone positioned at a computer with a process laid out on the computer screen and the ability to turn on a pump and open or close a valve. That is of course a very rudimentary way of describing the complex world of SCADA systems.

Granular Activated Carbon Building (GAC)

We are now at Step D on infographic contained within your study material. After the Membrane Building, the water then travels to the Granular Activated Carbon Building (GAC).

While the membranes are highly effective at removing impurities, the water can still contain dissolved particles that are not harmful, but can present taste and odor issues. To get rid of taste and odor issues, the water is filtered through with GAC. This part of the process reminds me of a clever joke a former professor told me during my college career… “Why do fish live in salt water? Because pepper makes them sneeze!” Haha Hehehe, now that was a very humorous joke about water, wasn’t it Class?

The GAC basins are very similar to activated carbon filters that can be purchased at your local grocery store (i.e. Brita Filters). As the dissolved particles come into contact with GAC, they are absorbed and become trapped.

The GAC basins are systematically backwashed, very similar to cleaning the membranes, to remove trapped impurities and polish the water. The GAC beds require periodic removal and replacement to ensure the best quality water.

Ground Storage Tanks and High Service Pump Station

Following polishing by the GAC process, the water is sent to Step E, the Ground Storage Tanks, where the disinfection process is completed.

The two circular structures are Ground Storage Tanks (GSTs). Each tank holds five million gallons of water.

Blowers located near the GSTs force air into the water (aeriation) to help remove disinfection byproducts such as TTHM. Disinfection byproducts are formed when chlorine is used to disinfect water and reacts with other organic matter. 

After aeriation, the water is ready to be pumped throughout the transmission system through High Service Pumps.

In the High Service Pump Station, six pumps that are capable of pumping up to 30 million gallons of water per day pump water through the transmission system to receiving customers throughout Montgomery County.

Surface Water Transmission Pipeline

The Surface Water Transmission (SWT) Pipeline, Step F in your study materials, is approximately 55 miles long and delivers surface water to customers, consisting of seven water providers and a total of 18 surface water receiving facilities.

The SWT Pipeline includes pipes made out of polyvinyl chloride (PVC) and ductile iron (DI) with diameters that range from 12 to 60 inches.

An example of a GRP customer or wholesale water supply provider is the  SJRA’s Woodlands Division . SJRA’s Woodlands Division provides wholesale water supply and wastewater treatment services to the 100,000-plus population of The Woodlands. Since 1975 the SJRA’s Woodlands Division has served as the wholesaler to the 11 municipal utility districts that provide retail services within The Woodlands. 

I mentioned my colleague Wells at the beginning of the process, but I failed to mention another associate that is simply brilliant, Woody. Woody is Wells’ twin brother and will explain what happens when you flush your commode in his  Where Does the Water I Use Go?  scholastic piece.

Surface Water Receiving Facilities

At each facility, the treated surface water is blended with groundwater and distributed by the retail water provider. An example of a retail water provider are the eleven Municipal Utility Districts (MUDs) that currently serve The Woodlands in Montgomery County. The  Woodlands Water Agency  is the central management agency for 10 of the MUDs. 

If you are still following along on the infographic we are at Step G.

San Jacinto River Authority - GRP Surface Water Receiving Facilities

Additional Processes at the Treatment Plant

The water treatment process from above removes particulates, solids, and other wastes. Additional processes are needed to treat and dispose of waste products and reclaim any water used for cleaning or solids transportation. The Solids Treatment Process removes the waste products. The Recycling Process recovers and recycles water back through the water plant for additional treatment.

The Solids Treatment Process – Sludge Thickeners and Clarifiers

During the water treatment process, a form of waste, also known as sludge, subsequently develops. Sludge is periodically removed from the Pretreatment Facility and is pumped to the Clarifiers and Sludge Thickeners. Here sludge is allowed to settle and concentrate into a thicker liquid and remove excess water.

The Solids Treatment Process – Belt Presses

The thickened sludge is piped to the Solids Dewatering building for further processing.

In the Solids Dewatering Building, the sludge flows through a belt filter press. The belt press removes excess water by squeezing the wet sludge through filter cloth and rollers, which forces the water out.

The result of this process is a cakey substance. The substance is then removed and disposed of in a landfill.

Water that is recovered from the process flows to the Process Water Recovery Basins and is held for the Recycling Process.

The Recycle Process

As water flows through the membranes, particulates left behind accumulate and must be backwashed to remove them from the membrane filter.

The backwashed water and particles are sent to Backwash Equalization Basins. This ensures that as little water is wasted as possible.

From there, any settled sludge flows to the sludge thickeners.

The clarified water returns to the Process Water Recovery Basins to mix with water from the belt press process. The recovered water from the backwash and belt press water is returned to the pretreatment basins for additional treatment.

Am I Receiving Treated Surface Water?

If you would like to find out if you are receiving treated surface water from this water plant, please click on the link below to open a new tab.

Within the Am I Receiving Treated Surface Water viewer, enter your address and click on the colored polygon surrounding your address.

*If your address location does not have a colored polygon associated with it (blue or green), your water provider might not be participating in the SJRA GRP and you do not receive any of the treated surface water from Lake Conroe. Addresses within the blue polygon represent SJRA GRP participants receiving treated surface water, while addresses within the green represent SJRA GRP participants not receiving treated surface water.

Works Cited

​​Intellectual property of all pictures included in this story map is the property of their respective owners.

 ​This story was initiated, designed, and created by the San Jacinto River Authority.

San Jacinto River Authority - GRP Surface Water Receiving Facilities