If you work in an industry like manufacturing, construction or oil and gas, waste generation is an inevitable part of your everyday operations. Correct disposal is essential, and proper liquid waste management is particularly critical because of its potential for unexpected leaks, discharges and runoff.
Fortunately, many options exist for ensuring effective, responsible, compliant liquid waste disposal. The guide below will discuss how to dispose of liquid waste and evaluate your waste disposal options.
The Importance of Proper Liquid Waste Disposal Methods
Proper liquid waste disposal is essential — so much so that disposal is often heavily regulated and tiny infractions could incur hefty fines. Your facility will need to pay careful attention to the details of liquid waste disposal to ensure your processes are correct and compliant.
Why is correct liquid waste disposal so critical? Here are a few reasons:
- Environmental protection: Improper liquid waste disposal can inflict grave damage on the surrounding environment. It can disrupt the balance of aquatic ecosystems and kill marine organisms. Or it can seep into the soil, kill plants, destroy natural habitats and cause biodiversity loss.
- Human health protection: Inadequate liquid waste disposal can also make people seriously ill. If waste fluids leak, spill or run off over the ground, they can contaminate the groundwater and surface water sources that people use for drinking. If treatment plant filters cannot address the contaminants, people may ingest them. They may develop gastrointestinal illnesses, heavy metal poisoning or other severe conditions depending on the composition of the waste.
- Aesthetic concerns: Improper disposal of liquid waste can give the disposal area an offensive smell. Though it may not harm residents directly, it can make their daily activities more unpleasant and lead to complaints. Proper waste disposal helps your company maintain good relationships with residential neighbors and feel good about contributing to the excellent air quality they enjoy.
Classifications of Liquid Disposal
Liquid waste may come in a few different forms:
- Sanitary sewage: Sanitary sewage typically comes from a home or community and contains human waste and wash water. It includes toilet, bath, laundry, lavatory and kitchen sink wastes. Its composition is typically about 99.9% water and 0.1% organic and inorganic impurities.
- Industrial sewage: Industrial sewage comes from facilities involved in manufacturing. The processes that produce industrial sewage span a range of operations, such as pharmaceuticals manufacturing, paper and textiles manufacturing, chemical processing and oil and gas refining. This sewage usually has a high chemical concentration.
- Storm sewage: Storm sewage consists of the surface runoff that flows into municipal sewers during heavy rainstorms. Storm sewage often contains dirt, twigs and other debris that screens at sewage treatment plants must filter out. It may also contain suspended and dissolved solids, organic matter and other substances it accumulates as it travels over the Earth’s surface.
- Mixed sewage: Mixed sewage combines two or three of the single sewage types. Storm sewage may mix with sanitary sewage on its way to the sewage treatment plant, or a standard sewage treatment plant may receive an influx of industrial wastewater from a nearby facility.
7 Liquid Waste Disposal Methods
Below are seven of the most common liquid waste disposal processes:
Dewatering works well to compact nonhazardous waste and make it more suitable for disposal. In this process, the facility generally pumps the liquid waste into a sturdy bag and removes the water, leaving only solid waste. A landfill typically does not accept free liquid, but the solid, nonhazardous waste can go to the landfill for disposal. The water receives filtration and treatment as necessary.
One common option for liquid waste dewatering, especially for sludge, is centrifugal dewatering and thickening. This process uses a cylindrical vessel to generate centrifugal force, which flings solids from the liquid and causes them to form a soft substance known as cake.
Sedimentation is similar to dewatering in that it separates water from solid waste. It uses gravity instead of centrifugal force to pull the two states of matter apart.
During sedimentation, a facility leaves its liquid waste in a sedimentation basin. As long as liquid waste flows quickly, its velocity is often enough to keep solid particles in suspension, so the design of a sedimentation basin reduces that velocity. As the wastewater flows slowly through the basin, solid suspended particles settle to the bottom in a layer of sludge.
The facility can then remove the solids, leaving the solid sediment waste behind. Once the water and solid waste have separated, the water can undergo treatment, and the solid waste can go to a landfill.
Alternatively, facilities can turn their liquid nonhazardous waste into compost. The facility first removes the water from the waste, leaving behind organic matter that contains nutrients like nitrogen, potassium and sodium. Using naturally occurring microorganisms, the facility can then turn the material into organic fertilizer that will also contain these beneficial nutrients to help crops and other plants grow.
Compared to many other methods of liquid waste disposal, composting is relatively inexpensive. It is also exceptionally easy on the environment — even advantageous for soil and plant growth.
Sometimes facilities dispose of their hazardous waste by incinerating it. The heat from specialized furnaces can remove acids, chemicals, oils, rock tailings, slag and other waste matter, leaving only water behind. There are two types of furnaces used for this technique:
- Fluidized-bed furnace: A fluidized-bed furnace is an industrial furnace that uses pressure to cause a bed of solid particulate matter or solid-fluid mixtures to behave like a fluid. These incinerators contain one heated, bubbling bed of sand, ash or limestone with oxygen pumped in to facilitate heat combustion. Their large size allows for complete, efficient burning.
- Multiple-hearth furnace: A multiple-hearth furnace uses many stacked chambers to incinerate large volumes of wastes at different stages, all at steady, consistent rates. Because the chambers are stacked, they are compact and easy to fit into cramped quarters, and they are also relatively inexpensive to build and install.
Incineration is not always an ideal method of liquid waste disposal. Unlike the techniques laid out above, incineration is hard on the environment because it releases toxic contaminants and greenhouse gases into the atmosphere. It can reduce air quality, exacerbate asthma and other respiratory conditions and contribute to climate change. Incinerators are also expensive to install, maintain and run. In some cases, though, facilities turn to incineration because it is effective and leaves little waste behind to require further disposal.
5. Root-Zone Treatment
Root-zone treatment is most useful for relatively clean domestic wastewaters like kitchen water and bathroom shower and sink water. This treatment is a complex method that sends liquid waste through a sedimentation tank and then through various additional filtration processes — including, ultimately, the roots of growing plants. The result is water that meets the necessary standards for release into the environment.
Root-zone treatment may employ a succession of filtration processes like these:
- Pretreatment sedimentation: The water first sits in a sedimentation basin so that some of its solid particles can precipitate out for easy removal.
- Anaerobic reactor: During the next step, the liquid waste might pass through an anaerobic reactor. The reactor typically contains a baffled design that creates many internal compartments for the water to flow through. As the water passes through, the microorganisms collected on the compartment surfaces digest more of the suspended solids.
- Anaerobic filter: An anaerobic filter contains a filter medium where microorganisms can form colonies. These microorganisms digest more of the suspended particles to make the liquid waste cleaner.
- Plant-filled gravel filter: Once the water has undergone the initial treatments, it flows through a gravel bed filled with live plant roots. The plants are often sturdy reeds that offer resistance to the water’s flow. As the plants respirate, they supply oxygen to the effluent and help remove the last remaining contaminants.
Root-zone treatment offers many benefits. It typically uses gravity — the water flows downhill from stage to stage, so pump and valve requirements are minimal. It is also exceptionally environmentally friendly — root-zone technology uses only 20% of the energy of a typical sewage treatment plant. And an established plant bed typically requires very little maintenance.
Because it contains so many elements, though, root-zone treatment can be expensive to perform, and its complex installation means it may not be available in some areas.
Liquid waste solidification involves adding binding agents to wastewater until the waste forms a compact, rigid, easily disposable solid. Many solidification processes use lime ash, sawdust, cement kiln dust, lime kiln dust, gypsum, phosphate or fly dust to add bulk and rigidity to liquid waste, or they may use asphalt or cement for added reinforcement. After solidification, companies can ship the solid blocks of waste to approved landfills for disposal or waste-to-energy facilities for incineration and energy generation.
Solidification often combines with a process known as stabilization. Solidification alters the waste’s physical properties, making it harder, stronger or less permeable and enclosing any hazardous contents. Stabilization makes it less likely for hazardous components to leak into the environment — for instance, by making them less mobile, soluble or toxic.
One well-known example of solidification and stabilization practices in action is the Defense Waste Processing Facility in South Carolina, which is slowly converting 36 million gallons of high-level liquid nuclear waste into glassified solid waste. This conversion process makes the waste more stable and manageable until a secure federal repository can provide long-term storage.
Some advanced, environmentally friendly solidification techniques can solidify liquid waste without adding other substances to it. These innovative techniques minimize waste and enable smaller landfill additions.
Solidification is relatively cheap and easy to perform, but the extra solid material tends to make for a tremendous amount of refuse. The excess weight and bulk can sometimes lead to higher transportation and disposal costs, and it may require a disproportionate amount of space in the landfill.
The remaining alternative is to dispose of the liquid waste as it is, often with the assistance of a professional waste management company. In this case, the facility collects its liquid waste in the appropriate drums. Then the waste management company picks them up, transports them and disposes of them according to applicable state and federal guidelines. This option is particularly appealing for companies that wish to remain compliant with regulations without investing significant time and energy into keeping up with them.
Considerations When Choosing Your Liquid Waste Disposal Method
No single waste disposal technique is most effective for every situation. When you choose a liquid waste disposal method, you’ll need to weigh the pros and cons, assess your waste generation patterns and disposal requirements and make a decision that best suits your needs. Below are a few considerations to keep in mind as you deliberate:
- Soil formation and stability: The disposal site you’re considering should have stable soil that can hold waste in place. Softer, looser soils may permit shifting and leaks. If this is the case in your area, you may need to choose a method like incineration that bypasses land disposal.
- Land space: The availability of adequate land for liquid waste disposal will also inform your choice. If space is minimal, you may find your disposal possibilities limited, so you may need to avoid solidification and other methods that would create massive quantities of waste.
- Waste quantity: Similarly, if your facility produces high volumes of liquid waste, you’ll need to choose a disposal method that can accommodate them. Though composting is good for the environment, you may not be able to spare the resources for it if your waste volumes are too high.
- Necessary treatment: Some liquid wastes contain minimal impurities and need only light treatment. Others are heavily contaminated and will require aggressive treatment before they are ready for disposal. For sanitary sewage and its high biosolid concentration, for instance, root-zone treatment would be insufficient. Make sure the disposal method you have in mind is thorough enough to keep you compliant with regulations.
- Well water sources: Look into whether residents in your area use well water. If so, find out the source of the water supply. You’ll want to make sure your disposal site is safely far away from the water source.
- Surface water sources: Similarly, if a proposed disposal site for your liquid waste is close to surface water sources, you’ll also need to keep away from those. A leak from the disposal site could cause contaminated runoff to flow into the surface water sources and jeopardize locals’ health and well-being.
- Water table level: The level of the water table for groundwater is also an essential consideration. If the water table level is high, disposal sites will need to remain shallow to avoid contaminating the water.
- Cost: Apart from environmental concerns, the expense of liquid waste disposal is also a significant factor. Evaluate the relative costs of the disposal technologies you’re considering and determine which will fit best into your facility’s budget.
Contact Environmental Recovery Corporation for Help With Liquid Waste Disposal
Now that you know more about various liquid waste disposal methods, you can make your choice easier by partnering with a trusted, innovative, industry-leading waste management company — ERC.
We are a full-service environmental company with extensive experience in handling all types of waste streams, including liquid waste, and disposing of them sustainably and responsibly. We provide compliant industrial wastewater treatment, liquid waste solidification, sludge and solvent waste removal and recycling and chemical waste management. You have numerous options to bring you peace of mind concerning your waste management operation’s safety and effectiveness.