Prompt Payback— Laundry Wastewater Recycling
Systems vary widely, but one can probably save you money on water and energy

By Randy Anderson

As water recycling becomes more mainstream in today’s commercial laundries, vendor offerings become more complex. There are very few systems on the market that are technologically alike, and the capabilities of different technologies vary widely. So, a quick overview of the markets for water recycling is in order.

But first, let’s define what water recycling is all about. Laundry water recycling refers to the collection of wastewater from washing machines, the filtering out of contaminants and the reuse of treated wastewater in the washing process. The economic benefits of recycling include a lower volume of water purchased from the municipality, a reduced waste stream discharged to the municipal sewer, and the capture and reuse of heat in wastewater that now flows to the sewer. There are also minor savings associated with the reduction in salt required to soften city water, the reduction in boiler chemistry due to lower consumption of steam and the reduction in drying times when warm water is used in the final rinse. The extent to which a system is able to provide these savings depends on the technologies involved and the percentage of water recycled.

Types of systems
There are several different types of recycling systems on the market. They range from simple rinse-water reuse systems to the more complex, high-capacity recycle systems. As the systems become more complex, the savings expand and the capital investment and maintenance requirements likewise can increase. To help explain the process, let’s define three distinct cycles in the washing of linens. The first is the wash cycle, followed by a bleaching cycle and finishing with a rinse cycle. One or more of each of these cycles is common when washing a load of linens.

Rinsewater reuse
The most basic system involves rinse water reuse. These types of systems have been around for many years and work with washer/extractors only. As the name implies, the system is designed to capture the wastewater from the rinse cycles only. This waste stream is fairly clean and is generally pumped to a holding tank before being used in the wash cycles of subsequent wash loads. Little or no filtration is required to reuse this water in the wash cycles and this process typically yields a 20% to 25% reduction in water usage. Since these systems lack filtration to remove organic matter from the wastewater (oils and detergents), it’s unsuitable for the bleaching cycles. In addition, the rinse water is typically cold to lukewarm, so there’s minimal energy savings associated with a rinse water reuse system.

One challenge an operator faces when trying to implement a rinse water reuse system is how to capture just the rinse wastewater. Typically a split trench is required and the washer/extractors will have to be equipped with two independent dump valves. The washers can then dump wash wastewater into one trench that leads to the sewers and dump reusable rinse wastewater into the second trench that leads to the reuse system. Since most laundries are not designed with this infrastructure, an alternative is to consider a slightly more advanced filtration system that collects all the wastewater, but only filters a small portion of it so that it can be used as wash water.

Wash water only
Wash water only recycle systems require some filtration since this type of system takes wastewater from all three washing cycles. Since a portion of the wastewater that is reused has come from the hot wash cycles, the energy savings can be significant. There are a few different variations of this type of system on the market today—some remove organic wastes and others don’t. If organics are removed, then the recycled water can be blended with fresh water and used for the bleaching cycle and perhaps the first rinse cycle. Depending on how many of the cycles utilize the recycled water; these systems can reduce water demand by 40%-60%. With all recycle systems, as water demand decreases, the amount of heat recovered increases. Thus the energy savings become a bigger factor. Wash water only systems shouldn’t be considered in medium and heavy-soil washing environments. Some of the more advanced systems that remove organics from the wastewater can also be used with tunnel washers.

High capacity recycle systems
The maximum savings associated with laundry wastewater recycling can be achieved with a high capacity recycle system. These systems collect all wastewater from the wash process and filter it to near potable-quality water for reuse as wash, bleach and rinse water in subsequent washes. As such, these types of systems are compatible with both washer/extractors and tunnel washers. Due to the soil loading in this type of wastewater, more complex filtering systems are employed that can require some maintenance in order to produce a good quality reuse water. These systems are capable of reducing water demands by 50%-90%. However, this significant reduction in water usage corresponds to an equal reduction in wastewater going to the sewer. If a laundry has a wastewater discharge permit, it is very important to look at the waste streams that enter the sewer from the recycling system.

Discharge considerations
The soil loading in your wastewater doesn’t disappear when you install a water recycling system. Instead, the soils must be collected and removed. Depending on the type of filters used, you will either have a solid waste that is periodically disposed of in the landfill, or a heavily concentrated liquid waste that is disposed of in the city sewer. Some systems will rely on ceramic or membrane-type filters that separate the wastewater into two distinct flows. One is clean and can be reused (permeate), while the other is now a concentrated soil flow that moves to the sewer (reject). This concentrate can be cost prohibitive in areas where tightly monitored sewer authorities charge excessive soil-loading fees, based on concentration limits (mg/l or ppm).

The discharge of concentrated wastewater can be avoided with a technology that physically traps the soils for future disposal in the landfill. With this type of technology, the wastewater-discharge profile changes very little from the current operation and could actually improve. In either case, the soils must be handled and disposed of, and it’s important to understand the differences and costs associated with each recycling option.

In addition, it’s important to understand that most recycle systems are not designed for heavy soil/industrial laundries and very few can handle medium soils. Ask your supplier about their capabilities and check references that correspond to your type of washing environment.
It should be noted that ceramic and membrane-type filters require large pumps to force the wastewater through the filter and into the two distinct flows. Therefore, pay careful consideration to the cost of electricity to operate the large pumps and check references on the maintenance and replacement costs for the membranes or ceramic filters.

Calculating savings and estimating ROI
The biggest dollar savings in recycling operations will come from reduced water and energy use. The water and sewer savings calculations are generally very simple. If a recycling system is installed in a laundry that runs a million gallons a month through its washing machines and the recycling system is designed to reduce water usage by 80%, then you should be saving 800,000 gallons per month. Multiply this number times your utility rate and the result is the estimated dollars saved.

Energy savings are a little more complicated. Below is a list of basic facts to help you approximate the current energy costs associated with heating water. By definition, one BTU (British Thermal Unit) is the amount of energy required to heat 1 pound of water 1 degree Fahrenheit. Therefore, it takes 8.3 BTU (8.3 pounds = 1 gallon) to heat one gallon of water one degree Fahrenheit. If using 500,000 gallons of hot water each month, city water is about 55° F and if heated to 150° F, energy usage is [(150° F – 55° F) x 500,000 gal x 8.3] = 394 million BTU. Since there are 100,000 BTU in a therm of natural gas, the savings are approximately 3,940 therms of gas per month. Assuming you have a recycling system operating at an 80% recycling rate, recycled water would be sent to the hot water heater or washers at 120° F rather than the 55° F coming from the city. Now the water requires minimal energy to heat from 120° F (recycled water) to 150° F (hot water). Energy costs would only be 1,245 therms, saving approximately 2,695 therms per month. However, since boilers and water heaters are only about 80% efficient, multiply the above therm calculation by 1.25 to get a more accurate reading of the energy savings that you can expect when using recycled water in the water heater.

With a better grasp of the savings associated with recycling your wastewater, it’s now possible to estimate your ROI. This is the amount of time required to generate enough savings from operating the recycling system before there’s real money in your pocket. First, determine the net monthly savings of running the system. Total all the water/sewer saving and energy savings and subtract the costs to run the system (maintenance, labor, parts, maintenance contracts, electricity costs, etc.) to determine the net savings from the operation. The payback calculation then becomes very simple; total all the costs to purchase the system (including installation, freight, equipment and interest costs), then divide by the net monthly savings to determine how many months into the operation your system will actually begin saving you money.

When comparing two systems side by side that have dramatically different costs and savings, you may need to look past the payback period to determine your best option. For example
n System A costs $100,000 and has savings of $50,000 a year and has a 2-year payback
n System B costs $50,000 with savings of $25,000 a year which also has a 2-year payback
Which system should you purchase? Well, based on the payback period alone, it doesn’t matter, since both have the same 2-year payback. However, looking deeper, you’ll notice that system A adds $50,000 to profits each year after the payback period while System B only adds $25,000 after the same payback period. From that standpoint, system A looks a lot more attractive. So do your homework. It could shape your final decision.

Benefits of wastewater recycling
The economic benefits of recycling wastewater from washing machines can be significant. With water/sewer and energy rates skyrocketing, paybacks on these systems can often be less than 12 months for those operating in high water- and utility-rate regions. Look at all the options and compare the different technologies on the market. Check references and determine the actual realized reduction in utility costs that the current users of the technology are enjoying. It’s also important to understand how the supplier is using the term ‘recycle percentage.’

Some suppliers use this number to refer to the percentage of wastewater reduction going to the actual sewer. Others use recycling percentages to explain the percentage of recycled wastewater in the supply of water now going to the washers. The difference between the two is the amount of water that goes to the dryers as wet linen and is lost to evaporation. This can account for as much as 15% of total water usage. For example, one supplier claming a 75% recycling rate may not be saving you as much money as another supplier claiming the same rate. What matters most is the amount of money you’ll save every month, minus the added operating costs for running the equipment. This includes maintenance costs for major parts and also should include labor hours either internally or through an outside service. The net amount is the actual savings you’ll realize.

The bottom line is that water recycling makes both economic and practical sense for most laundries today. Laundries washing heavily soiled linens still face a major challenge when exploring some form of recycling, but in many circumstances it still may be possible. Depending on the utility costs and current washer configuration, some form of water recycling will most likely make sense. The benefits far exceed the investment, and a payback generally is realized quickly. TR

Randy Anderson is chief information officer for Aqua-Recycle, Marietta, GA; call him at 866/272-9253 or e-mail randy.anderson@AquaRecycle.com.