Wastewater Treatment: MLS 051

• MLS 051 covers wastewater treatment, septic systems and solid waste management
• The course will be held in the 2nd Semester of SY 2024-2025
• It is part of the College of Medical Technology at Southwestern University PHINMA
• The lecturer is Lourenz V. Patentes, RMT

Wastewater

• Wastewater is the substance that remains after humans have used water for domestic or commercial purposes.
• It is also referred to as liquid waste or sewage.
• It consists of 99.9% water and 0.1% suspended and dissolved solids.

Wastewater Treatment

• The primary purpose of wastewater treatment is to improve its quality so that it can be released into a body of water safely.
• This prevents disruption of aquatic environments and health problems in humans like waterborne diseases and nuisance conditions.
• Most municipalities and large companies use wastewater treatment plants that incorporate at least primary and secondary treatment processes.

Primary Wastewater Treatment

• Primary wastewater treatment occurs in a sedimentation tank or clarifier.
• Wastewater remains in a quiescent condition for 2-4 hours.
• Heavier solid particles settle to the bottom, forming sludge which is a gooey, semi-solid mixture
• Above the sludge is an aqueous layer of wastewater, including many bacteria and chemicals.
• Scum (a layer of oils and fats) sits on top of the aqueous layer.
• The layers of sludge and scum are removed, and the clarified wastewater goes to the secondary stage of treatment.

Secondary Wastewater Treatment

• Aerobic bacteria are added, and mixed with clarified wastewater to break down the organic waste.
• This mixture flows to aeration tanks.
• Oxygen is continuously added in aeration tanks to support aerobic decomposition of organic waste into CO2, water, and minerals.
• This process takes 6-10 hours.
• Wastewater is then sent to sedimentation tanks, where solids and bacteria are separated from the treated liquid.
• Some treatment plants disinfect and discharge treated wastewater to water bodies, while others perform tertiary treatment.

Tertiary Wastewater Treatment

• This involves filtration through sand and carbon filters.
• Many remaining dissolved pollutants are removed during this stage.
• The treated water is finally disinfected and discharged.
• Chlorination is the least expensive way of disinfecting wastewater.
• Dechlorination is performed to prevent poisoning of aquatic life in streams or rivers downstream of the discharge point.

Septic Systems

• Septic systems are used where people in unsewered areas dispose of their wastewater.
• They have two major components—a septic tank and a buried sand filter or absorption field

Septic Tank

• This is a watertight concrete or fiberglass tank, buried in the ground at a distance from the house and connected by a pipe.
• Sedimentation occurs here.

Absorption field

• This is a system of trenches (dugout channels) where perforated pipes are surrounded by gravel.

Technologies for Excreta Disposal

• Cartage is the most basic form of excreta disposal in which feces are collected in a container and disposed of daily, e.g., bucket latrine or vault latrine.
• Latrines (Pit Latrine): Fecal matter is stored in a pit and left to decompose.
• Pit latrines do not require periodic emptying; once a pit is full it is sealed and a new pit is dug.
• Some pit designs are meant to be completely dry, while some use small quantities of water.
• Ventilation to remove odors and flies is incorporated into certain designs.
• Other types of latrines include Sanplat and VIP Latrine
• Septic tanks are a form of on-site sanitation that provides the convenience of a sewerage system.
• Septic tanks are linked to flush toilets and can receive domestic wastewater or sullage, making them appropriate only for households with water piped into the home.
• Aquaprivies are similar to septic tanks
• Aquaprivies consist of a large tank with a water seal, formed by a simple down pipe into the tank to prevent odor and fly problems.
• A drawback is water must be added each day to maintain the water seal.
• Unlike a septic tank, the aquaprivy tank is located directly below the house, but it requires periodic emptying.
• Sewerage systems are designed to collect excreta and domestic wastewater and transport them away from homes to a treatment and/or disposal point.
• All sewerage systems should be linked to a treatment plant, as the raw feces

Sewage Treatment and Reuse

• Stabilization ponds require more land, but are cheaper and easier to operate and maintain
• Stabilization ponds need fewer trained staff than other treatment systems.
• In stabilization ponds, sewage flows through a series of ponds where solid and liquid wastes undergo natural breakdown processes.
• Some of the demands for water, particularly for agriculture and fish breeding, can be met by reusing properly treated effluent
• Treated wastewater can be used to recharge groundwater resources
• Only the reuse of treated wastewater should be promoted
• Treated wastes should not contain pathogens because these could contaminate products/infect consumers, or be accidentally ingested by farmers
• Solid waste from pit latrines and sewage-treatment plants can also be a valuable resource for farmers as an organic fertilizer and soil conditioner.
• Wastewater reuse may increase the nitrate and chloride content of the soil, the effects of which has been linked to the "blue-baby" syndrome that can be fatal in infants.

Solid Waste Management

• Key strategies include minimizing waste generated per household
• And recycling waste whenever possible
• Solid wastes should be sorted for recycling, and for burying or burning

Household Solid Waste Management

• Composting involves the use of fruit and vegetable waste, animal dung, and even leaves from trees to break down and form a valuable soil conditioner and fertilizer.
• Organic waste can be chopped up, compressed into small bricks, dried in the sun, and then used to replace charcoal or wood in cooking.

Community Solid Waste Management

• Communal refuse pit: This is a pit dug near the community compound and filled with general refuse.
• Communal collection involves householders transporting their solid waste to the disposal site or may be organized

Special Solid Waste Management

• Health care solid waste requires special treatment and disposal
• Slaughterhouse solid waste contains decaying animal carcasses, blood and fecal matter
• Slaughterhouse waste is a significant source of pathogens and bad odors, which may also pollute water supplies.
• Industrial solid waste contains toxic chemicals that pose health risks and pollute the environment.
• Small-scale mining operations also use and produce toxic chemicals, such as mercury, and arsenic

Chemical Safety

• Follow manufacturers' instructions on use, storage, and disposal.
• Agriculture: use pesticides, dips, inorganic fertilizers with safety
• Industrial: car repairs, running motor vehicles with safety
• Household: cleaning agents with safety

Chemical Safety: Storage

• In a safe place, out of reach of children.
• Stores should remain locked; keys given only to authorized people.
• Well-ventilated, located away from water sources.
• Storage areas should have a shower or washing system in case of a toxic spill.

Chemical Safety: Handling

• Should be handled with great care.
• Toxic spills should be contained as soon as possible, far from communities.
• Appropriate PPE should be worn.

Chemical Safety: Disposal

• Proper disposal of toxic chemicals requires responsibility and action at both household and community levels.
• Old chemicals should not be indiscriminately dumped in the environment, as this can pollute both soil and water, and the chemicals may give off toxic fumes.
• Chemicals should be disposed of according to manufacturers' guidelines.
• Chemicals that have passed their "sell-by" date should be collected by trained staff and disposed of at special sites.