Energy Efficiency in Wastewater Treatment = Big Savings for Municipalities

Municipal wastewater treatment requires an enormous amount of energy, which comes at a high cost, both fiscally and environmentally. Energy costs continue to rise while municipal budgets shrink, creating unsustainable operating costs. Indeed, energy efficiency for wastewater utilities is no longer a choice, but a necessity. The good news is that there are many relatively inexpensive and easily implemented ways of controlling energy costs at wastewater treatment facilities, and the payback period can easily justify the investment.

VoltsThe first step towards making an informed decision about energy efficiency at a wastewater treatment facility is an energy audit. A quality wastewater energy audit takes into account energy efficient equipment replacement, operational changes, and process control, and includes conducting on-site observations, testing wastewater systems and equipment, and monitoring power costs and usage. The result of a well executed energy audit is a justifiable plan of action that provides optimal energy savings, a true road map to energy efficiency.

Once the audit results are in, a number of changes, both large and small, can be made to save on energy costs. Wastewater treatment plants can conserve energy in many ways, from changing light bulbs and upgrading motors to installing combined heat and power systems and other renewable energy technologies. Some energy efficient options are highlighted below:

Equipment & Collection System Upgrades

Variable-Frequency Drives

Variable-frequency drives (VFDs) modify the speed of electric motors by adjusting the amount of power being delivered. These precise drives adjust motor speed to match the exact energy demand needed at any given time. By controlling the amount of power used, VFDs provide significant cost savings to wastewater treatment facilities and to the environment. A good application for VFDs is the blowers on the aeration system. Dissolved oxygen probes installed in the aeration basin can provide real time measurement of oxygen concentration in the wastewater. This information can be sent to the VFDs to speed up or slow down the blowers to provide only the oxygen needed for the biological process to thrive. The result — significant savings and happy microbes.

fluorescent light bulbHeating, Cooling, and Ventilation Systems

Updated HVAC systems that incorporate energy-efficient technologies provide operational savings and reduce energy consumption. Like VFDs, the most cost-effective time to upgrade these systems is when they are already due for replacement.

Energy Efficient Lighting

Installing energy efficient lights and lighting systems is one of the easiest ways to increase energy efficiency at wastewater utilities. Replacing burnt-out lights with fluorescents or LEDs eases into the transition and makes it affordable. Dimmers, motion sensors, and time switches can be installed to save even more energy — and money.

Operating Strategies

Electrical Load Management

Strategies such as improving the power factors of motors, reducing peak demand, and shifting to off-peak hours all provide significant savings for wastewater treatment facilities.

Biosolids Management

Biosolids, or the solid organic matter that is a by-product of the wastewater treatment process, should be managed sustainably in order to reduce both environmental and economic costs. Sustainable biosolids management incorporates efficient methods of treatment, transport, and end-use. By implementing a sustainable biosolids management plan, such as pretreatment for minimizing sludge treatment and recycling/reuse of residual sludge, municipalities can reduce greenhouse gases as well as trucking miles, thereby saving money and generating energy.

Operational Management

Procedure ListWhile updating equipment is a great way to increase energy efficiency, even more important is training managers and staff to think and operate efficiently. Educating wastewater utilities’ staff on the importance of energy conservation and on best practices yields significant savings for wastewater utilities and the environment.

Inflow and Infiltration Management

Inflow and infiltration (I/I) in a wastewater facility’s collection system results in significantly higher costs to utilities. Increased flow requires additional processing, and results in higher demand to lift station pumps. In addition, systems are at an increased risk of becoming overloaded. Controlling I/I is a key step to becoming a more efficient wastewater treatment facility.

Energy Efficient Technology

Combined Heat and Power

Digester eggs at the Deer Island Wastewater Treatment Plant operated by the Massachusetts Water Resources Authority (MWRA) in Massachusetts
Digester eggs at the Deer Island Wastewater Treatment Plant operated by the Massachusetts Water Resources Authority (MWRA) in Massachusetts

Combined heat and power (CHP), or cogeneration, is a clean, efficient, and sustainable approach to generating power from a single fuel source. Wastewater treatment plants with anaerobic digesters installed produce methane gas as a by-product of digestion. Traditionally, these facilities convert the methane to carbon dioxide and release it into the atmosphere. However, a cleaner and more efficient way of managing methane is to actually utilize it as an energy source. CHP systems are designed to meet the specific energy needs of wastewater treatment plants, and can significantly enhance operational efficiency while decreasing energy costs. In addition, CHP systems are beneficial to the environment in that they reduce greenhouse gas emissions, which contribute to climate change, which contributes to water scarcity and degradation — a damaging cycle.

In Conclusion

Energy efficiency in wastewater treatment operations is certainly the wave of the future. Because of increased loads and decreased budgets, municipal wastewater treatment plants are finding it necessary to implement cost-effective solutions in order to operate sustainably. Implementing an energy audit and incorporating energy efficient strategies into day-to-day operations at wastewater treatment facilities will provide significant economic and environmental benefits, and provide a safe, clean future for generations to come.

Powering Vehicles from Discarded Food: East Coast Meets West Coast

food waste graphic useLast month, Massachusetts Governor Deval Patrick signed into law the Commercial Food Waste Ban, which will go into effect on October 1, 2014. This law targets commercial institutions who produce more than one ton of organic waste per week, such as hospitals, restaurants, schools, hotels, and supermarkets. Once the ban takes effect, this waste food, which accounts for 25% of the waste stream in the Commonwealth, will need to be recycled rather than discarded. Recycling food waste has many advantages. First, it brings awareness to businesses to simply be more mindful in food ordering, preparation, and potential donation in order to decrease the overall amount of food waste they produce. Next, it decreases food waste in landfills, and thus mitigates the amount of greenhouse gas entering the atmosphere from decomposition. Finally, it provides a clean energy source. And that is something this country desperately needs.

Anaerobic digestion (AD) is one way to dispose of organic waste that has the added benefit of producing clean energy. AD uses microbes to break down organic waste in an oxygen-deprived chamber, producing biogas, a clean and potent energy. Biogas is produced not just from food waste, but from any organic waste matter, including human waste, and is a clean energy option for heating and cooling, electricity, and powering vehicles. Wastewater treatment facilities that currently incorporate AD in their treatment processes could potentially be modified to handle food waste as well, and the Commonwealth is offering up $1M in grant funding for public facilities to do just that. In fact, the first grant of $100,000 has already been awarded to Massachusetts Water Resources Agency (MWRA) to process food waste at its wastewater treatment plant on Deer Island.

AD eggs at Newtown Creek Wastewater Treatment Plant in Brooklyn, New York Courtesy of New York City Department of Environmental Protection
AD eggs at Newtown Creek Wastewater Treatment Plant in Brooklyn, New York, photo courtesy of New York City Department of Environmental Protection

Connecticut and Vermont have passed similar laws, but they are using a more gradual approach. Both states currently only require businesses that are located within 20 miles of a suitable recycling facility and produce more than two tons of food waste per week to recycle, but expect full compliance by 2020. New York City is also implementing a food waste ban as a result of the success of its recently completed Food Waste Challenge, a six-month trial in which businesses voluntarily participated by donating unused food as well as diverting their scraps to a local treatment plant. The City noted that a key part of the initiative was food donation, as more than 25% of food waste diversion was a result of donations to local food banks. And businesses are supportive. Melissa Autilio Fleischut, president and CEO of the New York State Restaurant Association, commended the program and supported the litigation. “The Food Waste Challenge proves that sending less to landfills is good for both business and the planet,” Fleischut said in a press release. “The New York State Restaurant Association looks forward to working with the city to advance this initiative in a responsible way that works for everyone.”

On the other side of the country, waste-powered cars are swiftly becoming a reality. Hyundai, who has been working with the University of California, plans to begin leasing a fuel-cell version of its Tucson crossover that can travel about 480 kilometers on a tank of hydrogen, which is produced from AD and has zero emissions. The eco-friendly Tucson, which will only be available to California residents, has low lease rates which include free fuel from nearly a dozen hydrogen pumps around the state. Toyota, Honda, Mercedes-Benz and GM are starting to sell hydrogen cars in California as well.

A recently opened filling station in California that utilizes methane from landfill sources
A recently opened filling station in California that utilizes methane from landfill sources

California has long been a pioneer in green technologies. However, Massachusetts is the first state in the nation to actually implement a comprehensive ban on organic waste. While utilizing waste for energy has largely been voluntary and thus slow-moving, this legal mandate will force large-scale organic waste processing facilities into production, either through retrofitting of existing facilities or new construction. And these new processing centers will produce large amounts of biogas. So will the east coast finally start seeing the alternative fuel filling stations and vehicles that are currently reserved only for the west coast? Let’s hope so. If we could combine east coast legal mandates with west coast alternative fuel technology, the nation could see zero emissions vehicles running on discarded organic scraps and sewerage. Keep excess garbage from our landfills while powering pollutant-free vehicles? Now that’s a win-win.