With local water stress like availability and access to a clean water source, price, and wastewater treatment driving water reuse, manufacturers are considering cost-effective water filtration systems to reduce their water footprint, waste, and chemical consumption.
Industrial wastewater reuse poses challenges because initial feed water characteristics can differ from facility to facility.
Why is filtration in water treatment so crucial for wastewater reuse?
Filtration is the process of removing particles suspended in water. Straining, flocculation, sedimentation, and surface capture are some of the techniques used to remove waste. Filters are classified according to their primary technique of capture, which is either the exclusion of particles at the surface of the filter medium (straining) or deposition inside the media (in-depth filtering).
Filtration is very important for many commercial and industrial process water and wastewater reuse applications. In reality, pumping wastewater from somewhere like a refinery, food and beverage, textile or oil produced water application requires pre-filtration due to high amount of suspended solids in these typical applications. In fact, there are typically many filtration and treatment steps in these applications to ensure that the treated water meets the required discharge or reuse standard. In addition, filtration in water treatment ensures reduced operating cost on downstream polishing water treatment systems.
Filtration is very important for many commercial and industrial process water and wastewater reuse applications. In reality, pumping wastewater from somewhere like a refinery, food and beverage, textile or oil produced water application requires pre-filtration due to high amount of suspended solids in these typical applications. In fact, there are typically many filtration and treatment steps in these applications to ensure that the treated water meets the required discharge or reuse standard. In addition, filtration in water treatment ensures reduced operating cost on downstream polishing water treatment systems.
For example, in the oil and gas industry, water discharge may contain hundreds of parts per million (ppm) of oil and total dissolved solids levels over 200 ppm, whereas discharge water in the pulp and paper industry may contain more fibrous solids. In addition, the required water purity may vary. Users may need the water discharge to be slightly upgraded to potable (drinkable) standards, or brought to ultrapure water quality. In addition, the importance of water filtration in water treatment processes such as process water or wastewater discharge or reuse is critical.
Below are a few examples of advanced treatment processes that need prior filtration for successful operation:
Particle Filtration
Particle filtration is a physical or mechanical process that separates solids from fluids. Particle filtration is typically defined as the filtration of particles larger than 1 micron and is one of the first filtration steps in industrial wastewater treatment. Common technologies that are used for fine-particle filtration include bag filters, cartridge filters, multimedia filters, and self-cleaning filters.
Because industrial wastewater characteristics can vary intensely, depending on the industry, it is common to use multiple technologies to process the water. The properties of the solids in the water, including particle size, shape, density, stickiness, and quantity, as well as other materials in the water such as oil, determine which filter technologies are used.
Disinfection
Disinfection systems involve the treatment of microscopic pathogens by way of oxidation. However, interference due to particulate matter decreases the treatment efficiency of these units.
For instance, UV disinfection uses ultraviolet radiation to destroy bacteria. The wavelength of the light travels from the light source through the fluid to the targeted contaminants. However, if suspended particles are within the influent, they will physically block the light waves from reaching the pollutants that need to be disinfected appropriately.
Membrane Filtration
When fine-particle filtration alone does not provide sufficient water reuse quality, membrane filtration can be used to purify the wastewater further. The required treatment steps are dictated by the water’s final end use as discharge, in wash stations, cooling towers, and processes; as high-pressure boiler makeup water; or for semiconductors. The cleaner the water must be, the more sequential technologies must be used.
Membrane technologies and integrated membrane systems have become the industry standard for water reuse in which the highest water quality is required. Reverse osmosis (RO) membranes are needed to reduce contaminants such as dissolved solids and small organic molecules to an acceptable level.
Micro- or ultrafiltration (MF/UF) methods often are used as pre-treatment for reverse osmosis. Concurrently, double membrane filtration provides a multi-barrier solution for bacteria or pathogen removal to help facilitate access to safe water.
Advanced Oxidation
Advanced oxidation processes refer to a set of chemical treatment procedures designed to remove organic materials in water and wastewater by oxidation. Advanced oxidation processes (AOPs), in a broad sense, are a set of chemical treatment procedures designed to remove organic (and sometimes inorganic) materials in water and wastewater by oxidation through reactions with hydroxyl radicals. However, proper pre-filtration with some other treatments can keep them out entirely.
Coagulation
Whether it’s a chemical or electrochemical coagulation system, a certain level of pre-filtration is key to effective treatment. Coagulation systems are typically used to coagulate and flocculate smaller particles that don’t settle out very quickly or efficiently. The addition of chemical additives or electrical currents is what drives the process. However, these processes typically work best at a particular concentration range for the target constituents. Filtering out larger particles prior to these systems will ensure that these systems work at their maximum efficiency. In addition, higher concentrations of suspended particles would require adding more chemicals or supplying more voltage to the system to operate effectively. To reduce operating costs, the importance of filtration in water treatment is advisable.
