By Thomas Renner
Something quite old is leading to something quite new in the wastewater treatment industry.
In systems ranging from Florida to Egypt, solar power is the driving force behind the technology in wastewater treatment plants. Solar drying is a technique that is being used increasingly by operators of medium-sized and large wastewater treatment plants. The process reduces sludge disposal costs and protects the environment.
In all types of climates and a wide range of wastewater plant sizes, solar dryers by HUBER are helping communities save money and support the environment. In Sanford, Florida, a treatment plant with a capacity of 8.5 million gallons per day was recently installed. It is similar in construction to a plant in Egypt that has been officially awarded by Guinness World Records as the largest water treatment plant in the world with a capacity of 5.6 million cubic meters per day.
The common theme in both plants, and others, is the sun. The process extracts water from sewage sludge, and while using solar energy to treat wastewater is not a revolutionary idea, doing so on a large scale is a far more recent development.
“We had a very basic dewatering system where we were getting about 16 percent solids,’’ said Anne Nelson, the lead plant operator at the Sanford plant. “With the HUBER system we get about 75 percent solids, and it’s very dry. The 16 percent that we got from the other system was not as dry, kind of like a gelatin mold. The solids from the HUBER system are not quite soil, but it’s very dry, it reduces the number of trucks we have to send out and is more easily used.”
Solar ‘Sludge Turners’
The Bahr El-Baqar plant is the standard by which all future solar systems will be measured. It holds three Guinness World records, but the process in Egypt, Sanford, and other systems is roughly identical except for plant capacity.
The HUBER Sludge Turner SOLSTICE® units work in greenhouses. The turner travels on rails and repeatedly rearranges the sludge on the ground. During the movement, the sludge is dried by solar energy. At the end of the drying lane, the sludge turner picks up the dry granules in the tool that repositions the sludge during its forward movement. The dry material is relocated to a recess in the ground, then collected and transported to a container.
The facility in Sanford includes a 410-foot long drying field, which is 39 feet wide. The greenhouse is slightly larger, to accommodate loading, unloading and maintenance areas. The dryer can accept 4,790 wet tons per year.
The system takes a solid mixture that is 78 percent moisture and water and 22 percent dry solids and converts it to 75 percent dry solids. Evaporation reduces the amount of wet tons that need to be hauled offsite to 1,405 tons per year.
The system in Egypt includes 128 sludge turners and can accept approximately 475,000 tons of sludge per year. The system is constructed on more than 39 acres and includes 16 greenhouses.
The costly infrastructure project – it cost about $700 million in U.S. currency – is critical in the region. The Bahr El-Baqar drain is one of the most polluted in the country. Industrial waste and sewage from Cairo, along with agricultural runoff, pesticides and fertilizers, end up flowing into the drain. Water quality scores range from 37-48, a rating that is marginal or poor. Much of the water is used for irrigation and fishing.
Reliance on energy chains
An important component to the HUBER Sludge Turner SOLSTICE® units are energy chains manufactured by igus. The company, based in Germany, runs its North American operations out of Providence, R.I.
The energy chains include the company’s chainflex cables, which provide reliable data transfer and energy supply for the sludge turners. The energy chains in the application in Egypt travel approximately 100 meters, while the Sanford system e-chain is 128 meters or nearly 140 yards, about 1.5 football fields.
“Energy chains are the best solution for cable guidance on long travels,’’ said André Großer, HUBER SE Product Manager. “It requires little room, protects the cable, and is easy to install and maintain.”
The chainflex cables are also critical to the sludge turner. Three individual cores and a CFPE cable, all with a TPE outer jacket, ensure connection to the cable. Data exchange is with an igus CFBUS cable with a PUR outer jacket and those cables are designed specifically for use in energy chains. They also include an abrasion-resistant outer jacket and special interior stranding.
Changing the game
The wastewater treatment systems are just one of the innovations in the rapidly expanding field of using solar power to solve problems in many industries.
In the wastewater industry, treatment plants have been equipped with photovoltaic systems to supply the facility with its electricity requirements. The solar-powered sludge turners can add another layer of renewable energy to the equation.
There are, however, many more applications related to civil engineering that are using energy emanating from the sun.
In Austria, Ecotherm Austria developed a steam-generating solar boiler. A series of moving mirrors mounted on the roof of a building direct sun rays onto a collecting pipe filled with water. The process produces CO2 neutral steam.
A far less complex system is a rubbish bin developed by a company in Finland that compacts waste with solar energy. The system reduces operating costs and ecological footprint, and ensures that waste is compressed in a ratio of 6:1.
Like the SOLSTICE®, the products include components from igus. The company’s self-lubricating products are durable, withstanding the effects of extreme temperature, wind, water, and dust. The company has more than 17 years of experience in the solar sector, and its range of products – energy chains, bushings, cables, and more – have been proven in multiple projects that rely on solar power.
Wastewater management is not an issue that will grasp the attention of most members of the community. It is messy, complicated and is hardly the topic of most dinner table conversations. It is an important issue, especially in an era where everyone is more conscious of the environment.
“It is important that municipalities and utilities have the information they need to treat and manage biosolids,’’ Wayne Cascio, acting assistant administrator science in the U.S. Environmental Protection Agency said in the awarding more than $5 million in funding for research to determine the health and environmental risks from pollutants in biosolids. “These grants will help us leverage resources and knowledge to ensure the latest science is being used to protect public health and the environment.”
Sanford is well aware of the issues. In 2014, a sewage processing company abruptly closed its doors and filed for bankruptcy. The closure required Sanford to pay an additional $10,000 per month to haul sewage biosolids offsite.
As the world seeks more systems that rely on renewable energy, however, more solutions such as the HUBER Sludge Turner SOLSTICE® will be developed to help in the fight against climate change.
“As a company that is working in the environment, we are always looking for solutions,’’ said André Großer, HUBER SE Product Manager. “We not only want to make water clean, but we also want to reduce our reliance on electric energy. We are developing the process and we are on the right track. In any project, we are concerned about the environmental impact and look for the best practices to protect our environment.”
Thomas Renner writes in engineering, construction, architecture, and other trade industry topics for publications in the United States and Canada.