Energy consumption accounts for a large proportion of the operating costs of wastewater treatment plants. How to use new technologies and renewable energy to improve the energy efficiency and reduce energy consumption in the water supply and water treatment process has become the focus of many wastewater treatment plants in the world. Today we will introduce to you the application of solar energy in several sewage plants in the United States.

Washington Suburban Sanitation Commission, Senecaand Western Branch Wastewater Treatment Plant, Germantown & Upper Marlboro, Maryland

The Washington Suburban Sanitary Commission (WSSC) has established two independent 2 MW solar photovoltaic power plants, each of which can offset the annual grid-connected power purchase of approximately 3278MWh/year. Both photovoltaic power generation systems are built in open areas above the ground, next to the sewage treatment plant. Standard Solar was selected as the EPC contractor, and Washington Gas Energy Services (WGES) was the owner and PPA provider. AECOM assists WSSC in reviewing the design documents of EPC suppliers to ensure the high quality of the system.

AECOM also submitted environmental permit documents to the Maryland Department of Environment (MDE) to ensure that the solar photovoltaic system complies with local environmental regulations. Both systems are connected to the client of the 13.2kV/ 480V step-down device and located between the transformer and any relays or circuit breakers that protect the sewage treatment plant. Due to the choice of interconnection points and solar power generation that sometimes (though rarely) exceeds the on-site power consumption, new relays have been installed to prevent the power output from returning to the grid. The interconnection strategy of DC Water’s Blue Plains wastewater treatment plant facilities is very different from that of WSSC and requires multiple interconnection methods, mainly considering that there are two main utility power feeders branching to three main electric meters and corresponding medium voltage circuits.

Hill Canyon Wastewater Treatment Plant, Thousand Oaks, California

Hill Canyon Sewage Treatment Plant was built in 1961, with a daily processing capacity of approximately 38,000 tons, and is known for its excellent environmental management. The sewage plant is equipped with a three-stage treatment device, and the treated wastewater can be reused as reclaimed water. 65% of the power consumption on site is produced by a 500-kilowatt cogeneration unit and a 584-kilowatt DC (500-kilowatt AC) solar photovoltaic system. The solar photovoltaic system is installed in an overflow reservoir as a drying bed of biosolids, as shown in Figure 8. These modular components are installed on a single-axis tracker above the highest water level, and all electrical devices are installed on one side of the channel to minimize water intrusion. The system is designed to only need to install the vertical pier anchors on the existing concrete pool bottom plate, reducing the amount of construction required for traditional piling or foundations. The solar photovoltaic system was installed in early 2007 and can offset 15% of the current grid purchases.

Ventura County Waterworks District, Moorpark Reclaimed Water Plant, Moorpark, California

Approximately 2.2 million gallons (approximately 8330m3) of sewage from 9,200 users flows into the Moorpark Water Reclamation Facility every day. The 2011-2016 strategic plan of Ventura County detailed five “key areas”, including “environment, land use, and infrastructure”. The following are the key strategic goals in this specific field: “Implement cost-effective energy-saving and emission-reduction measures through independent operation, regional planning, and public/private collaboration.”

In 2010, Ventura County Water District No. 1 cooperated with AECOM to investigate photovoltaic systems. In July 2011, the region received a 1.13 MW photovoltaic project performance award fund at the Moorpark Waste Reclamation Facility. The region has gone through a long Request for Proposal (RFP) process. Finally, in early 2012, RECSolar was awarded the authorization for the project to begin the design and construction of the photovoltaic system. The photovoltaic system was put into use in November 2012 and obtained a parallel operation permit.

The current solar photovoltaic system can generate about 2.3 million kilowatt-hours of electricity each year, which can almost offset 80% of the electricity purchased by the water plant from the grid. As shown in Figure 9, the single-axis tracking system generates 20% more electricity than the traditional fixed tilt system, so the overall electricity production has been improved. It should be noted that when the axis is in the north-south direction and the bit array is in the open area, the single-axis tracking system has the highest efficiency. The Mookpark Waste Recycling Plant uses adjacent farmland to provide the best place for photovoltaic systems. The foundation of the tracking system is piled on the wide flange beam underground, which greatly reduces the construction cost and time. During the entire life cycle of the project, the region will save approximately US$4.5 million.

Camden County Municipal Public Utilities Administration, New Jersey

In 2010, the Camden County Municipal Utilities Authority (CCMUA) set itself a bold goal of using 100% renewable energy that is cheaper than local electricity to process the 60 million gallons generated per day ( About 220,000 m³) sewage. CCMUA realizes that solar photovoltaic systems have such potential. However, the CCMUA wastewater treatment plant is mainly composed of open reaction tanks, and traditional rooftop solar arrays cannot form a certain scale to supply power.

Despite this, CCMUA is still open tender. Mr. Helio Sage, who participated in the tender, expressed his belief that through some additional projects, a photovoltaic system similar to a solar garage will be deployed above the open sedimentation tank. Since the project only makes sense if CCMUA can achieve immediate energy savings, the design of the scheme must not only be robust, but also cost-effective.

In July 2012, the CCMUA Solar Center launched a 1.8 MW solar photovoltaic power generation system, which consists of more than 7,200 solar panels and covers an open pool of 7 acres. The innovation of the design lies in the installation of the 8-9 foot high canopy system, which will not interfere with the use, operation or maintenance of other equipment pools.

The solar photovoltaic structure is an anti-corrosion (salt water, carbonic acid and hydrogen sulfide) design, and a modified carport canopy manufactured by Schletter (a well-known supplier of photovoltaic bracket systems, including carports). According to PPA, CCMUA has no capital expenditures and is not responsible for any operation and maintenance costs. The only financial responsibility of CCMUA is to pay a fixed price for solar power for 15 years. CCMUA estimates that it will save millions of dollars in energy costs.

It is estimated that the solar photovoltaic system will generate about 2.2 million kilowatt-hours (kWh) of electricity each year, and the performance based on the CCMUA interactive website will be better. The website displays current and accumulated energy production and environmental attributes, and reflects the current energy production in real time, as shown in the figure below.

West Basin Municipal Water District, EI Segundo, California

West Basin Municipal Water District (West Basin Municipal Water District) is a public institution dedicated to innovation since 1947, providing drinking and reclaimed water to the 186 square miles of west Los Angeles. West Basin is the sixth largest water area in California, serving nearly one million people.

In 2006, West Basin decided to install solar photovoltaic power generation systems on its reclaimed water facilities, hoping to obtain long-term financial and environmental benefits. In November 2006, Sun Power helped West Basin install and complete the photovoltaic array, which consists of 2,848 modules and generates 564 kilowatts of direct current. The system is installed on the top of the underground concrete processing storage tank in the area. West Basin’s solar photovoltaic power generation system can generate about 783,000 kilowatt-hours of clean renewable energy each year, while reducing the cost of public facilities by more than 10%. Since the installation of the photovoltaic system in 2006, the cumulative energy output as of January 2014 was 5.97 gigawatts (GWh). The picture below shows the photovoltaic system in West Basin.

Rancho California Water District, Santa Rosa Reclaimed Water Plant, Murrieta, California

Since its establishment in 1965, Rancho California Water District (Rancho California Water District, RCWD) has provided drinking water, sewage treatment, and water reuse treatment services to areas within a radius of 150 square miles. The service area is Temecula/RanchoCalifornia, including Temecula City, parts of Murrieta City, and other areas in Riverside County.

RCWD has a forward-looking vision and is highly sensitive to the environment and strategic costs. Faced with increasing public facility costs and annual energy costs of more than 5 million US dollars, they considered solar photovoltaic power generation as an alternative. Before considering solar photovoltaic systems, the RCWD board of directors evaluated a series of renewable energy options, including wind power, pumped storage reservoirs, etc.

In January 2007, driven by the California Solar Energy Program, RCWD received a performance award-only $0.34 per kilowatt-hour of electricity within five years under the jurisdiction of the local public utility. RCWD exercises PPA through SunPower, without capital expenditure. RCWD only needs to pay for the electricity generated by the photovoltaic system. The photovoltaic system is funded, owned and operated by SunPower.

Since the installation of RCWD’s 1.1 MW DC photovoltaic system in 2009, the area has been enjoying many benefits. For example, the Santa Rosa Water Reclamation Facility (Santa Rosa Water Reclamation Facility) can save US$152,000 in costs a year, offsetting approximately 30% of the plant’s energy needs. In addition, as RCWD chooses Renewable Energy Credits (RECs) related to its photovoltaic system, it can reduce more than 73 million pounds of harmful carbon emissions in the next 30 years, and has a positive market impact on the environment.

The solar photovoltaic system is expected to save up to 6.8 million US dollars in electricity costs for the region in the next 20 years. The solar photovoltaic system installed in the RCWD Santa Rosa plant is a tilt tracking system. Compared with the traditional fixed tilt system, its energy production rate of return is about 25% higher. Therefore, it is similar to the single-axis photovoltaic system and fixed Compared with the tilt system, the cost-effectiveness is also significantly improved. In addition, the oblique tracking system requires a larger area to avoid occluding the shadow line by line, and must be oriented in a straight line. The oblique tracking system has its limitations. Similar to the single-axis tracking system, it must be built in an open and unrestricted rectangular area.