Physical treatment processes are the most direct approach to managing landfill leachate, with significant effectiveness. These processes utilize a series of methods such as physical adsorption, gas stripping, and membrane separation to effectively separate and remove harmful substances in the leachate. 

Gas Stripping

This technology introduces gas into the wastewater, allowing it to mix and contact the liquid thoroughly, causing the dissolved ammonia nitrogen in the water to cross the gas-liquid interface and transfer to the gas phase, thus achieving ammonia nitrogen removal. Air is typically used as the carrier gas in this process. Currently, this method is widely used in many urban landfills, achieving an ammonia nitrogen removal rate of about 60% to 80%, with very significant treatment results.

Adsorption

This technology primarily uses activated carbon as the adsorption medium. Due to its large specific surface area and well-developed pore structure, activated carbon can capture and fix the organic matter and heavy metals in the leachate as it flows through, thereby removing pollutants. Activated carbon adsorption technology is well-established in wastewater treatment. Studies show that this technology removes approximately 75% of the total organic carbon (TOC) in landfill leachate, achieves an 85% removal rate of chemical oxygen demand (COD), and removes up to 95% of ammonia nitrogen (NH₃-N). 

Membrane Separation

Membrane separation technology refers to a series of methods that use specific membranes to selectively allow different components in a liquid to pass through. Using polymer separation membranes, it can effectively separate and concentrate target substances in the solution. This technology system includes microfiltration, ultrafiltration, nanofiltration, and reverse osmosis. In current leachate treatment practices, nanofiltration and reverse osmosis are the most widely used membrane separation technologies. 

Nanofiltration

The separation performance of nanofiltration membranes is between ultrafiltration and reverse osmosis, with a molecular weight cutoff range of approximately 200 to 1000 daltons, and a pore size of about 1 nanometer. It is particularly suitable for separating dissolved components with sizes around 1 nanometer. In leachate treatment processes, nanofiltration is often used as a pretreatment step, and its permeate can meet discharge standards. If stricter salt removal is required for the effluent, a reverse osmosis system is typically connected in series after nanofiltration for further desalting. 

Reverse Osmosis

Originally used in seawater desalination, reverse osmosis technology has recently been extended to the concentration treatment of urban landfill leachate. This technology demonstrates excellent purification performance in reducing COD, NH₃-N, and salt concentrations in landfill leachate.