Whether you own, operate, or help manage a municipal or industrial facility that deals with wastewater, it’s important to understand how wastewater treatment can play a significant role in the overall health of your business, especially when it comes to meeting effluent regulations. This is an important part of the wastewater treatment process to consider, as ignoring it could earn your company various fines or lawsuits and pose a potential threat to public health if you are failing to meet these guidelines.
The guidelines that affect your facility will vary depending on its location, industry, and whether the effluent is being discharged into the environment under a National Pollutant Discharge Elimination System (NPDES) permit or to the local publicly owned treatment works (POTW) facility.
This article breaks down seven ways your facility might not be meeting these regulations and how you can fix it:
1. Your effluent has a high level of biochemical oxygen demand
Regulations often limit the amount of biochemical oxygen demand, or BOD, your facility is allowed to discharge. BOD refers to the amount of dissolved oxygen needed by aerobic biological organisms to break down organic matter into smaller molecules. When these levels are elevated, this can deplete the oxygen needed by other aquatic organisms to live, leading to algal blooms, fish kills, and harmful changes to the aquatic ecosystem where the wastewater is discharged. For this reason, many effluent regulations place limitations on these levels, ensuring local waterways are preserved and left unharmed.
When soluble organics are consumed by bacteria, they are converted to carbon dioxide and biological floc, which are both then settleable from the effluent. Reducing the organic content of the effluent and improving BOD levels, the process mentioned (called biological oxidation) is a popular method to control BOD and is achieved by fostering the right balance of “food” and organic matter. This can be achieved with the proper method of aeration, whereby air in introduced into the effluent in order to increase the rate of this biological oxidation which, in turn, increase the level of settleable solids that can then be removed from the effluent by process of filtration or clarification.
2. Your effluent contains too many total suspended and dissolved solids
Many effluent limitations include some kind of guideline on the level of total suspended solids (TSS) or total dissolved solids your facility is allowed to discharge.
TSS, or the organic and inorganic solid material suspended in the water, can harm aquatic life when present in high concentrations in wastewater. TSS can decrease levels of oxygen in aquatic environments and kill of insects. They can also scale and foul piping and machinery.
TDS are any anions, cations, metals, minerals, or salts found in wastewater. They can cause issues with aquatic life, irrigation and crops, and they can also seep into groundwater. TDS can be generated in wastewater from just about any industry.
Depending on the level of TSS and TDS your facility is seeing in its wastewater and the regulations set by your local effluent guidelines, your methods and the degree in which you implement them will vary. In general, these are some of the treatments useful for reducing TSS:
- Coagulation: This process starts off with an assortment of mixing reactors, typically one or two reactors that add specific chemicals to take out all the finer particles in the waterby combining them into heavier particles that settle out. The most widely used coagulates are aluminum-based such as alum and polyaluminum chloride. Sometimes a slight pH adjustment will help coagulate the particles, as well.
- Flocculation: When coagulation is complete, the water enters a flocculation chamber where the coagulated particles are slowly stirred together with long-chain polymers (charged molecules that grab all the colloidal and coagulated particles and pull them together), creating visible, settleable particlesthat resemble snowflakes.
- Sedimentation: The gravity settler (or sedimentation part of the wastewater treatment process) is typically a large circular device where flocculated material and water flow into the chamber and circulate from the center out. In a very slow settling process, the water rises to the top and overflows at the perimeter of the clarifier, allowing the solids to settle down to the bottom of the clarifier into a sludge blanket, which is then pumped out of the bottom into a sludge-handling or dewatering operation.
- Sand or carbon filtration: Gravity sand filters are big areas where they put two to four feet of sand, which is a finely crushed silica sand with jagged edges. The sand is typically installed in the filter at a depth of two to four feet, where it packs tightly. The feed water is then passed through,trapping the particles. Next, the water is passed through an activated carbon filter, where the leftover particles are adsorbed.
TDS reduction is a bit more complicated endeavor. If the contaminants are metal-based such as calcium, magnesium, or iron a simple chemical addition to the clarification process can be added to reduce these. If they are sodium, chloride, or other highly soluble ions, demineralization and/or evaporation may be required.
3. Your effluent has an increased amount of nitrates and phosphates
If large amounts of nitrates and/or phosphates are not removed from wastewater and these nutrients are discharged into local environments, they can increase the BOD and lead to extensive weed growth, algae, and phytoplankton. This can lead to eutrophication, or the deoxygenation in a body of water, killing the organisms and potentially leading to hypoxia or environmental dead zones. They can enter the wastewater stream a variety of ways, including human and food waste, detergents, and pesticides. For these reasons, limitations on these contaminants are usually strictly enforced.
If your facility isn’t meeting your nitrate and phosphate effluent levels, the following methods might be useful:
- Nitrate removal: Nitrates can be removed by several methods, including ion exchange, reverse osmosis, or conventional biological treatment and denitrification. Treatment usually is a combination of technologies, so for the best solution for your facility, be sure to work with your wastewater treatment specialist.
- Phosphate removal: An effective way to remove phosphates from you wastewater stream is often coagulation/chemical precipitation, depending on the types of phosphates present. Some biological treatments, such as the use of an anaerobic reactor (converts organic matter to methane and carbon dioxide) and aeration tank (injects oxygen to encourage biological floc formation), can be useful, as well.
4. Your wastewater contains oil and grease
Oil and grease are “hydrophobic,” which means they tend to repel from water and cling to surfaces free from water. High amounts of oil and grease in wastewater can clog sewer and drainage pipes in addition to harming human health and killing aquatic life, depending on the concentration and type of oil/grease. Often introduced into wastewaters as byproducts of food production, these contaminants are strictly regulated from being released with your effluent.
Some facilities that see large amounts of oil and grease in their wastewater will use dissolved air flotation (DAF). This device that removes the oil by dissolving air in the stream under pressure. When the bubbles float to the surface, they attach to the oil and grease so they can be skimmed off the top of the surface. Another method to successfully remove oil and grease might include some types of filtration, such as ultrafiltration or activated carbon.
5. Amount of water being discharged is more than your limited volume
Does your area have connection fees for discharging treated wastewater? Many times the fee is based on the volume of water your plant requires and varies based on whether you are discharging to the local municipal facility or into the environment. Regulations are typically stringent and are becoming more so every day, as some facilities might not be able to accommodate a high volume of effluent.
In order to comply with your local regulations and avoid expensive fees, measures to reduce your wastewater effluent can include treating your effluent for reuse or even zero liquid discharge. When done efficiently, this can help save your facility energy in processing waste as well as how much water you’ll need for your process. Reverse osmosis, nanofiltration, ultrafiltration, and other technologies (such as ion exchange) can help your facility recycle your wastewater for reuse. Depending on your process and the quality of water required for your process, your treatment needs might vary.
6. You’re not keeping up to date with regulations in your industry
Wastewater effluent regulations change all the time, and it’s important to keep up to speed with these changes. They also vary depending on the industry your company serves as well as where your facility is located.
It seems obvious, but make sure you reach out to your local regulators. They might be able to provide you with a representative for your area that can relay any changes to your facility. It is also useful to have a wastewater treatment expert in the area who is familiar with the changing regulations. They can often help your facility keep your effluent quality in compliance. In short, a little effort in being prepared can go a long way in helping your facility avoid fees and having your permit to discharge revoked.
Meeting local POTW or NPDES discharge regulations should remain a priority for your facility. Wastewater treatability studies can help your facility determine how to meet these regulations, so be sure you consider testing your wastewater streams prior to implementing the technology to think might solve your contamination issues. This can help you save time and cost in the long run. For more information about what a wastewater treatability study is, see our blog article here.
SAMCO has over 40 years’ experience custom-designing and manufacturing wastewater treatment systems, so please feel free to reach out to us with your questions. For more information or to get in touch, contact us here. You can also visit our website to set up a call with an engineer or request a quote. We can walk you through the steps for developing the proper wastewater treatment solution and realistic cost for your system.
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