Treating wastewater is an extremely involved process. With so many variables at play, numerous challenges related to both operations and treatment processes exist. With the right products and strategies, though, wastewater treatment plants can increase their efficiency and the quality of the treated water they discharge. Here are some of the most common wastewater treatment problems and solutions.
Wastewater Operational Challenges
Some of the challenges of wastewater treatment are on the operational side of things. Some of the most common hurdles involve infrastructure, energy consumption, staff and regulations. Here are four examples:
A recent survey of water industry professionals found that aging infrastructure was the top concern in the sector. The American Society Of Civil Engineers (ASCE) gave wastewater a D+ on its 2017 infrastructure report card. Pipelines, tunnels, treatment facilities and other infrastructure must be maintained to ensure efficient and safe wastewater treatment. The costs of maintaining this equipment are high, and if it becomes damaged, it can drive expenses even higher. According to ASCE, water and wastewater investment needs total $150 billion through 2025. ASCE also identified a $105 billion gap in funding.
An initial step to updating infrastructure is the implementation of asset management programs, which can improve the understanding of investment needs and direct a plan for making the necessary investments. ASCE has put forth potential solutions, including reinvigorating the State Revolving Loan Fund under the Clean Water Act, fully funding the Water Infrastructure Finance and Innovation Act (WIFIA) and preserving tax-exempt municipal bond financing.
Energy consumption is one of the most considerable expenses in operating a wastewater treatment plant. The energy use intensity (EUI) of wastewater treatment plants in the United States ranges from less than 5,000 British thermal units per gallons per day (kBtu/GPD) to more than 50 kBtu/GPD with a median of 10 kBtu/GPD, according to Energy Star.
Improving energy management practices, investing in more efficient equipment and making changes to treatment processes all have the potential to reduce energy use at wastewater plants and, therefore, reduce costs. Using fine screens during primary treatment, using membrane technology during aeration and directly treatment high-concentration return streams are examples of changes to processes that can decrease energy consumption.
The staff of wastewater treatment plants is crucial to its successful operation. To be able to perform their job duties efficiently and safely, staff need adequate training and certification, which can take up considerable amounts of time and resources. The work of wastewater treatment plant staff can also be challenging, especially during times of high demand. Staff often need to be on-call 24 hours each day and must complete technically complex tasks to maintain and repair pipes, valves and electrical equipment.
Having a well-defined plan for hiring, training and managing staff can reduce training-related costs and make these processes more efficient. Proper management and training will result in improved job satisfaction and performance. Safety should be an integral part of any training program. Many facilities are also increasing the amount of automation they use, which can reduce costs and improve worker safety.
Regulations, as they relate to wastewater treatment plants, change regularly and, in some cases, can increase costs for facilities. Not keeping up with regulatory changes can lead to fines, fees and even permit revocation.
Plant managers need a proactive plan in place for staying informed about regulations and addressing new requirements quickly. Because rules change, plant design should include some degree of flexibility by, for instance, leaving space for new equipment. Plant management strategies should keep an eye on the future by allowing for operational flexibility and ensuring adequate funding is consistently available.
Wastewater Treatment Process Problems
Wastewater treatment processes are highly technical and include a multitude of variables. Here are 12 of the most common process problems wastewater treatment plants and their potential solutions face.
Due to the wear and tear of regular contact with sewage water, the concrete surfaces of wastewater treatment plants begin to erode. Harder water and higher turbidity can increase the pace of erosion. Erosion increases maintenance costs and reduces the life of the equipment.
Applying protective coatings to surfaces can help slow the pace of erosion. You can also use repair composites to fix erosion damage and substantially improve the condition of damaged surfaces. When designing systems, plants can also use materials and designs that are more resistant to erosion to reduce future maintenance costs and improve plant performance.
Wastewater treatment facilities must contend with a flow rate that frequently varies. Plants need to be prepared to handle these variations and understand what their peak demand will be. If they're not, the system may experience upsets and turbidity issues.
To prepare for this variation, plants need to take an organized approach to predict peak demand. They can then use holding tanks to manage these peak demands. Variable controls for chemical feed systems can also help manage this. If you can not automate chemicals, you will need to increase the frequency of testing.
Incorporating variable flows on feed treatment equipment and excess flow buffering or holding capacity into system design can help plants balance flow variations.
Another challenge is variation in turbidity — the cloudiness of water due to its containing particles. Turbidity variation can negatively impact process and effluent quality if not handled adequately, even to the point of not meeting quality standards. It can also increase the amount of sludge produced.
To combat these issues, plant design should consider seasonal turbidity flow and note any changes it may see. Designing a treatment system to be slightly oversized will help accommodate turbidity variations. You should also include a recycle system so you can retreat water if it doesn't meet quality standards after the first treatment.
Including variable controls on your chemical feed systems and oversizing the sludge handling system can also help accommodate variations in turbidity.
Silica, magnesium, calcium, iron, aluminum and other contaminates can cause scale build up in wastewater treatment operations. This buildup can reduce the amount of water that can flow through a system, increase energy coats,as well as that system's overall effectiveness.
If scale buildup occurs, workers will need to remove it to prevent it from negatively impacting the system's performance.The use of chemical scale inhibitors can effectively prevent scale build up saving labor and energy costs.
Wastewater treatment plants themselves produce waste that the facility must dispose of. Disposing of this waste and complying with requirements can be costly. Unfortunately, secondary waste often does not get enough attention when designing facilities, which can increase costs associated with it.
Wastewater treatment plants typically dispose of secondary waste via discharge to the environment or a municipal facility. Plant managers need to make sure they understand all permit requirements related to secondary waste disposal. They should negotiate permissions in advance so the plant can meet discharge requirements and operate efficiently.
Bad odors are a natural occurrence at wastewater treatment plants, but they can be troublesome if they're excessive or drift into public spaces. Odors may cause complaints from the public, which can harm the plant's reputation. They can also worsen the work environment at the facility.
The first step in solving odor-related issues is identifying their source. Then, you can use various methods to help reduce them. Adding chemicals or using deodorizing misting systems can help, as can covering the source with an industrial-grade cover that keeps the smell trapped inside. You can then remove the cause and treat it elsewhere to prevent odors from spreading to public places.
Regulations require biochemical oxygen demand (BOD), a measure of the number of organics in water, to remain at certain levels to prevent oxygen depletion in waterways. Oxygen is also necessary for the decomposition process of wastewater. Keeping BOD at the correct levels and dealing with the resulting byproducts can be challenging.
Wastewater plants can control BOD by aerating the waste stream, which encourages biological oxidation. This process produces solids that either filtration or clarification can remove.
Disposing of sludge — the residue created during physical, chemical and biological treatment — is a significant process and environmental challenge. Plants must find long-term, safe and sustainable solutions for dealing with sludge. The procedures are different than those for scale since sludge is a softer substance in the form of a buildup of solids or oil. It typically builds up in low-flow parts of the boiler system. Excess sludge buildup can impede heat exchange, which drives up energy costs. It can also damage equipment and cause unsafe pressure conditions.
You can prevent sludge from building up through filtration or the use of chemical sludge conditioners. If sludge does form, you can blow it out of the system. After removing the residue, you may be able to recycle it, as it often contains nutrients and organic matter that make it useful as a fertilizer in the agriculture sector.
Wastewater treatment plants use flocculants to bring particulate suspended solids together into clusters called floc, which makes it possible to remove them from the water. This process, called flocculation, is an essential part of the wastewater treatment process. Sometimes, however, a condition called pin-floc or deflocculation occurs in which the floc particles are very fine and have poor settling characteristics, making it difficult to remove the solids.
Extreme underloading and the presence of toxic substances can cause pin-floc, so avoiding these triggers can help to prevent it. If it does occur or continues to occur with the influence of either of these causes, you may need to apply a settling aid.
High amounts of nitrates and phosphorous create challenges, but also opportunities, for wastewater treatment plants. These nutrients are crucial to plant growth, but when they enter waterways in high amounts, they can cause algae blooms. Then, these large algae growths deplete oxygen levels in the water and make it uninhabitable for fish. Nitrogen and phosphorous pollution are common in areas with large agricultural sectors.
Because of this environmental hazard, wastewater treatment plants must remove excess nutrients from water before discharging it into the environment. Doing so is costly and can be challenging.
Recent research has revealed a way that wastewater treatment plants can remove excess nutrients from water while also earning money in the process. Scientists at Rice University used wastewater as a feedstock for growing algae-based biofuels. The researchers were able to grow high-value algae while removing higher than 90 percent of nitrates and more than 50 percent of phosphorous from the water.
Another common wastewater treatment challenge is high levels of total suspended solids (TSS) and total dissolved solids (TDS) in discharge. Regulations set limitations for these levels to preserve water quality, which treatment plants must follow. When TSS and TDS levels are higher than usual, this can present challenges.
TSS reduction solutions include clarification and carbon or sand filtration. Reducing TDS levels is more complicated and typically involves the use of chemicals, demineralization, evaporation or a combination of these approaches.
Fats, oils and grease (FOG) do not mix well with water. If the amount of FOG in wastewater is exceptionally high, it can cause severe problems. It may clog pipes and infrastructure. If effluent with too much FOG is discharged, the FOG may increase BOD, float to the surface and trap trash and other materials. Exceptionally high amounts of FOG may prevent oxygen from reaching the water, causing septic conditions.
To prevent clogging and other issues, you must remove FOG from the water through chemical or mechanical means. Other methods involve manual removal, but these may be less efficient.
Finding the Right Partner and Products for Wastewater Treatment
Wastewater treatment is challenging, but having the right products and the right partners to back you up makes all the difference. Brenntag can help you meet regulatory requirements while helping you make your plant more efficient and improve your outcomes.
We provide a wide range of products for treating water, including natural flocculants, filtration media, heavy metal removal products and more. We also offer scale inhibitors, odor control products and other items to improve your plant processes. Additionally, we provide logistics solution and on-site consulting.