How to Recycle Wastewater

In a world where water is becoming scarcer and costlier, recycling wastewater is an integral part of the solution. Not only does it improve local water supplies, but it also saves energy costs by saving energy usage.

Wastewater treatment can be accomplished through various methods, but the most popular one is Return Activated Sludge. This combines mechanical and chemical systems with biological processes to eliminate traces of chemicals and dissolved solids from the water.

Biological Treatment

The biological treatment of wastewater is an efficient method for eliminating pollutants from water. Utilizing bacteria and other microbes to purify contaminated waters, biological treatments are widely used in food and drink industries, oil/gas industries, as well as chemical plants.

During this process, bacteria consume pollutants as food and reduce them to non-toxic compounds. This helps ensure that water can be disposed of safely and meets predetermined standards.

Wastewater contains a range of pollutants, such as domestic and industrial sewage, run-off from fertilisers and rainwater. When these pollutants enter the water they can deplete oxygen essential to fish and other aquatic life while fueling the growth of harmful algae.

Water treatment with biological processes can be accomplished using various techniques, such as trickling filters, pond-based systems, lagoons and dissolved air flotation (DAF). These treatments use oxygen provided by aeration to activate microorganisms that break down organic waste.

Bacteria help decompose organic matter into CO2, NH3, and H2O, which is then pumped away from the tank.

These systems employ bacteria to filter out various pollutants from wastewater and other materials, potentially eliminating the need for chemical treatment steps.

Activated sludge is the most widely employed biological treatment process for municipal and industrial wastewater, as well as sewage. It utilizes microorganisms that break down organic matter to produce aeration products like carbon dioxide, nitrates and hydrogen sulfide.

Some variations of this process utilize extended aeration or oxidation ditches to further filter out suspended solids from wastewater. The primary goal of secondary biological treatment is to eliminate all remaining dissolved and colloidal organic matter from effluent, in order to minimize odors and other potential pollutants.

Another advantage of this type of system is its versatility; it can be designed to treat wastewater at all BOD levels. Furthermore, it is energy efficient and suitable for treating large volumes of waste.

Chemical Treatment

Chemical treatment of wastewater utilizes chemicals to purify it and prevent the release of hazardous pollutants into the environment. This process includes oxidizers and disinfectants that reduce bacteria, pesticides, and other hazardous materials in wastewater.

Chemical treatment can effectively remove many pollutants from wastewater, such as metals, pesticides and organic compounds. To do this, chemicals that combine water-based with solvent-based components are employed – these may either be added directly into the liquid form of the wastewater or dissolved within it for efficient removal.

For instance, chlorine is a commonly used oxidizer that can be added to wastewater to eliminate pollutants. Other effective oxidizing agents include ozone and hydrogen peroxide.

Another commonly used chemical for wastewater treatment is sodium hypochlorite, which can be dissolved in water to eliminate harmful bacteria and microorganisms. This process also works well at eliminating toxic heavy metals from wastewater.

Other chemicals useful in wastewater treatment include coagulants and flocculants. Coagulants destabilize particles while flocculants make particles easier to settle by decreasing their negative electric charges.

In many cases, chemicals are added to wastewater before mechanical filtration in order to help the wastes settle more evenly, leading to less sludge and a cleaner final product.

This type of treatment can also be effective at eliminating contaminants that are difficult to filter out of water, such as grease and oil. These substances are typically handled the same way other pollutants are handled; this could include chemical coagulants, biocides, and odor control products.

These are essential steps in the wastewater treatment process. Utilizing chemicals can guarantee that the wastewater is free of microorganisms, making it suitable for recycling and reuse.

Chemical treatment can be an efficient and economical method for recycling water. However, it’s essential to remember that chemicals have a limit before they have an adverse effect on the water supply.

Membrane Bioreactors

Membrane Bioreactor (MBR) is a wastewater treatment process that utilizes membrane technology in lieu of secondary clarifiers, enabling recycling liquid effluent from the head of the plant. MBRs offer several advantages over traditional activated sludge processes such as higher solid concentrations and enhanced process control.

Membrane bioreactors are widely employed for the treatment of wastewater from various industries, both industrial and commercial. Furthermore, they play a significant role in municipal wastewater recycling initiatives.

MBR systems consist of aeration tanks and membranes installed in series to supply oxygen to bacteria that break down organic matter to create biodegradable compounds. They’re commonly employed at centralized wastewater treatment facilities as well as retrofitting onsite sewage treatment plants.

Depending on the design of a bioreactor (iMBR), the aeration tank may be inside or outside. Either way, membranes are placed either inside or on top of the aerobic tank to filter out dissolved organic material and solids from liquid effluent.

Although this practice is widely used, it can lead to fouling due to the presence of fine solids that clog the pores of the membrane and can only be removed through physical and chemical cleaning cycles. A more energy efficient and cost effective alternative than an iMBR is an sMBR which uses airlift mode but has a high energy consumption.

Membranes have many applications beyond wastewater treatment; they can also be employed to create value-added products such as hydrolysis of triolein, the production of glycerides and biodiesel from waste oil.

Another potential application of membranes is in the treatment of food waste. Microbial enzymes can be immobilized on membranes to break down sugar content in waste materials and make them useful for producing animal feed or other value-added chemicals.

At present, research into the use of membranes in value-added product formation is still in its early stages. However, it can be improved through high cell concentrations within a bioreactor and eliminating inhibitory products from the effluent. By integrating membranes into these biological processes, one could potentially produce various value-added items such as methanol, methane and hydrogen gas.