Reverse Osmosis vs. Electrochemical (advanced) Oxidation for Industrial Wastewater Treatment

This article analyzes wastewater treatment processes reverse osmosis (RO) and electrochemical oxidation (EO) for stakeholders in the industrial sector. We will explain how RO and EO work in industrial wastewater treatment and take a look at the pros and cons of each process. Whether you’re a factory owner or manager, this article will enhance your understanding of RO vs. EO wastewater treatment systems for improved decision-making.

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ClearFox® Reverse Osmosis Scheme

How does Reverse Osmosis work for Industrial Wastewater Treatment?

Reverse osmosis (RO) is a modern wastewater treatment solution that separates dissolved impurities from contaminated water with membrane technology. RO systems use between 150 to 600 psi to force water through superthin membranes. When pressure is applied on the side of stronger concentration, the liquid is pushed through the membrane, leaving the majority of dissolved material behind.

In industrial wastewater treatment, reverse osmosis separates the waste stream into a permeate stream (low concentration) and a concentrate stream (high concentration). This is typical of a one stage system. In a two stage system, the concentrate stream is fed through a second RO system. The greater the number of stages, the more effective the recovery of water. The permeate stream can also be fed through a second reverse osmosis system. This is known as a second pass and can greatly increase the quality of the permeate stream.

Pretreatment plays a critical role in reverse osmosis industrial wastewater treatment. This step protects the membrane against organic fouling, mineral scaling, and chemical degradation. Before conducting RO, identify and eliminate potential foulants. Ideally, your RO system should be customized with advanced pretreatment technology for best removal rates. After RO treatment, you can reuse the water in production or dispose of it safely.

Pros of Reverse Osmosis Wastewater Treatment

  • Cost-effective: RO systems deliver reusable treated water. You can reuse RO water for production to cut costs.
  • Eco-conscious: RO is an eco-friendly solution compared to industrial wastewater treatment processes that require holding, transporting, or the use of chemicals.  
  • Integration: You can integrate RO systems with an existing filtration unit to achieve up to 80% rinse water recycling.
ClearFox® Reverse Osmosis

Cons of Reverse Osmosis Systems for Wastewater Treatment

  • Inconsistencies: The outcome of RO treatment varies depending on the pretreatment and contaminants used in production. 
  • Clogging: RO systems use membranes with super-tiny pores, prone to clogging. You’ll need to invest more in routine maintenance to ensure optimal performance. 
  • Filter Replacement: Using RO filters without adequate pretreatment increases the risk of organic fouling, mineral scaling, and chemical degradation. An RO system with inefficient filters cannot fulfill its purpose. Remember, filter replacement isn’t free.  
  • Membrane Limitations: RO membranes cannot block contaminants that are smaller than the size of the pores. Feedwater quality should meet the requirements set by the membrane manufacturer. 
  • Demineralization: RO water is deionized of all essential minerals. The RO process also requires chemical additives to reduce CO2 that can traverse the membrane and decrease the pH levels. 
  • Pretreatment Requirements: You’ll need to check cation/anion balance and BOD/COD levels and pretreat your wastewater before RO treatment. 
  • Slow and Energy-Intensive: Pushing metric tons of wastewater through the membrane takes time and consumes energy.

How does Advanced Oxidation work in Industrial Wastewater Treatment?

Unlike reverse osmosis which uses membrane technology to separate pollutants from wastewater, advanced oxidation transforms the pollutants in wastewater into harmless substances through oxidation reactions.

Oxidation reactions occur when free radicals and oxidants are generated. Electrochemical oxidation (EO) is a method which uses electrical energy to achieve this. Electrochemical oxidation is one of the most established methods of complex wastewater treatment and the kingpin of advanced oxidation.

The electrochemical oxidation (EO) process uses electrolysis to remove dissolved contaminants in industrial wastewater. EO systems comprise anode and cathode connected to an external power source. Energy input flows through industrial wastewater, oxidizing and degrading the contaminants. Once electrical energy is supplied, direct oxidation occurs on the surface of the anode (negative electrode) where the pollutants become degraded. Indirect oxidation occurs when powerful oxidants such as hypochlorite, chlorine, or hydrogen peroxide are generated and react with the pollutants in the wastewater.

EO systems come in a wide range of designs and operation modes to address diverse wastewater treatment requirements, including the quantity and composition of the water. Advanced EO systems like Clearfox DiOx use diamond-coated boron-doped electrodes to remove a wide range of pollutants. These units achieve a higher removal efficiency than systems with standard electrodes. Diamond-coated electrodes have strong electrochemical stability, good conductivity, and high corrosion resistance. They are ideal for treating industrial wastewaters with very high TDS, such as oil and gas wastewater.

Pros of Electrochemical Wastewater Treatment Systems

  • Biodegrade: State-of-the-art electrolysis processes have a degrading character on organic load. EO systems provide residue-free mineralization. They remove substances that are difficult or impossible to biodegrade. 
  • Long-lasting: Boron-doped diamond electrodes extend the system’s lifespan. Oxidized layers on diamond coatings strengthen and stabilize the electrodes, eliminating corrosion. 
  • Eco-friendly: EO is eco-conscious, health-friendly, and safe because it doesn’t use chemicals. Diamond-coated electrodes are sustainable solutions for the future, degrading chemicals while providing high efficiency and lower energy consumption (OPEX). 
  • Hassle-free: Clearfox DiOx offers fully-automatic modular EO units, allowing for plug and play. Thrice the benefits – rapid installation, simple operational management, and low maintenance. 
  • Disinfectant Effect: Hydroxyl radicals formed on diamond-coated electrodes during the oxidation process disinfect the wastewater while reducing power consumption.
ClearFox®DiOx in process
ClearFox® DiOx Model

Cons of Electrochemical Wastewater Treatment Systems

  • By-Products: The electrolysis process can form undesired substances, such as perchlorate. Depending on the feed water, certain byproducts generated by EO may require separate disposal. In most cases, this can be avoided with pretreatment. 
  • High Upfront Cost: EO systems combine several cutting-edge technologies. So, they cost more than alternative wastewater treatment solutions up front. However, they are more robust and require less maintenance than RO systems.
  • Flow Rate Constraints: EO units for treating highly contaminated industrial wastewater can handle volumetric flow rates up to around 500 m3/d. Electricity consumption is proportional to the volume of water, impeding the treatment of higher volumetric wastewater flow rates.
  • Costly Electrodes: EO electrodes with diamond coatings cost more than typical electrodes for processes like electrocoagulation. Price-intensive electrodes also increase operating costs.

RO vs. EO, bottom-line?

As a facility owner or manager, you need the best solution to protect your business interests. Electrochemical oxidation outperforms reverse osmosis in mission-critical aspects of industrial wastewater treatment. EO systems don’t have membrane limitations and filter replacement costs. Although RO systems cost less at the outset, electrochemical processes have the advantages of being robust, easy to operate, and adaptable to fluctuations in wastewater flow with simple adjustments to the power supply. Complex wastewater producing applications such as textile, finishing, metal, paper, landfill leachate and chemical production can expect high purification performance with EO and in particular with boron-doped diamond electrodes due to superior conductivity, stability, yield and resistance to corrosion. The initial investment may be greater than reverse osmosis treatment but the long term ROI is greater. Overall, EO is the best process for complex industrial wastewater treatment. You can rely on Clearfox DiOx to exploit all EO benefits.

ClearFox® DiOx for industrial wastewater treatment

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