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Transcript of Wastewater Treatment
Almario, Anabelle "Ann" E.
Bermas, Joseph M.
Catabay, Sean Ivan E. Wastewater treatment is the process of taking wastewater and making it suitable for discharge back into the environment. Wastewater can be formed by a variety of activities, including washing, bathing, and using the toilet. Rainwater runoff is also considered wastewater. No matter where it comes from, this water is full of bacteria, chemicals, and other contaminants. Wastewater treatment reduces the contaminants to acceptable levels so as to be safe for discharge into the environment. Liquid waste or sewage discharged into a river or the sea. Refers to the residual, semi-solid material left from industrial wastewater, or sewage treatment processes There are two major waste streams discharge from a wastewater treatment :
"Effluent" &"Sludge". Why Do We Want to Treat Wastewater?
Treatment of wastewater is an essential process that prevents contamination and the destruction of our waterways, drinking water resources and natural water resources. Wastewater is approximately ninety-nine percent water and only one percent solids. The removal of these solids and disinfection of the water before discharge is the basic concept of wastewater treatment. If wastewater is not properly treated, then the environment and human health can be negatively impacted. These impacts can include harm to fish and wildlife populations, oxygen depletion, beach closures and other restrictions on recreational water use, restrictions on fish and shellfish harvesting and contamination of drinking water. Here are some examples of pollutants that can be found in wastewater and the potentially harmful effects, these substances can have on ecosystems and human health: Decaying organic matter and debris can use up the dissolved oxygen in a lake so fish and other aquatic life cannot survive; Excessive nutrients, such as phosphorus and nitrogen (including ammonia), can cause eutrophication, or over-fertilization of receiving waters, which can be toxic to aquatic organisms, promote excessive plant growth, reduce available oxygen, harm spawning grounds, alter habitat and lead to a decline in certain species; Chlorine compounds and inorganic chloramines can be toxic to aquatic invertebrates, algae and fish; Bacteria, viruses and disease-causing pathogens can pollute beaches and contaminate shellfish populations, leading to restrictions on human recreation, drinking water consumption and shellfish consumption; Metals, such as mercury, lead, cadmium, chromium and arsenic can have acute and chronic toxic effects on species. Other substances such as some pharmaceutical and personal care products, primarily entering the environment in wastewater effluents, may also pose threats to human health, aquatic life and wildlife. Wastewater Treatment Process
The first stage of the treatment process uses screens to remove the larger solid inorganic material such as paper and plastics. This is followed by the removal of particles such as grit and silt which are abrasive to plant equipment.
This next stage is a biological process which breaks down dissolved and suspended organic solids by using naturally occurring micro-organisms. It is called the activated sludge process.
The settled wastewater enters aeration tanks where air is blown into the liquid to provide oxygen for mixing and to promote the growth of micro-organisms. The “active biomass” uses the oxygen and consumes organic pollutants and nutrients in the wastewater to grow and reproduce.
From the aeration tanks, the mixture of wastewater and micro-organisms passes into a secondary sedimentation tank (also known as a clarifier) where the biomass settles under gravity to the bottom of the tank and is concentrated as sludge.
Some of this sludge is recycled to the inlet of the aeration tank to maintain the biomass, hence the name for the process – activated sludge. The remainder is pumped to anaerobic digesters for further treatment.
The clarified wastewater is discharged from the secondary clarifier and passes through for Tertiary Treatment.
All wastewater treatment plants use disinfection for tertiary treatment to reduce pathogens, which are micro-organisms which can pose a risk to human health.
Chlorine is usually dosed into the treated wastewater stream for disinfection. However, some waterwaste treatment plant uses large ponds in which sunlight and other micro-organisms reduce the pathogens. Additional treatment may be required if the treated wastewater is reused for purposes such as irrigation of food crops or where close human contact may result. Sludge Effluent Preliminary Treatment Secondary Treatment Tertiary Treatment Maintaining domestic waste water treatment systems The water treatment process