Sustainable Wastewater Treatment

TAN KAI SIN0315213

TAN CHUU YEE0315097

LOW CHEE YING

0319126WONG YUN SHI

0315225CHEONG KHA MAN

0319456 ELEY CHONG SHU

HUI

0319458

Lecturer: Kam Kenn Jhun

Wastewater used water or liquid that contains impurities or pollutants in the form of solids, liquids or gases or their combinations.

generated by human due to various activities (daily activities, commercial activities, industrial activities).

The final discharge of wastewater will normally onto the land (receiving bodies of water may be ponds, lakes, streams, rivers, seas, etc.).

It is harmful and will affect people health if wastewater being disposed into the environment without any treatment processes.

Wastewaters can be classified as: Domestic wastewater

- aka municipal/sanitary wastewater, simply sewage.

- used water which has been discharged from the

residential, commercial and industrial area of a city,

and collected through sewage system.

- generally is 99.9% water and contains only 0.1% of

organic and inorganic solids and also microorganism(bacteria).

Industrial wastewater

- generated by large & medium scale industries.

- manufacturing industries produce a large volume of high

strength wastewaters.

Treatment

partial reduction or complete removal of excessive impurities contain in wastewater.

Usually wastewater treatment is mean the reduction or removal of the solids from wastewater since impurities are generally due to the presence of solids in wastewater.

Wastewater treatment methods classified into:

i) physical unit operations

ii)chemical unit processes

iii)biological unit processes

The treatment units are designed to carry out particular

functions on the principles of either one or a combination

of the means employed.

Based on the means used, treatment methods have been

broadly classified as unit operations and unit processes.

Unit operations

- treatment in which the application of physical forces to treat sewage.

- Physical unit operation includes screening, mixing, flocculation, sedimentation, floatation, elutriation, vacuum filtration, heat transfer and drying.

Unit processes

- treatment in which the removal of pollutants by the

addition of chemicals or the use of biological mass or microbial activities.

- Based on the type of agent used, unit processes can be further classified as chemical unit process and biological unit process.

Chemical unit process treatment method in which reduction or removal is brought about by

chemical reaction (adding chemical).

- chemical neutralization: to control or adjust the system pH

- chemical coagulation : to remove colloidal particles by chemical

destabilization and flocculation

- chemical precipitation: to enhance the removal of suspended

solids, phosphorous, heavy metals and Biochemical Oxygen

Demand in specific system conditions

- chemical oxidation: to remove grease, ammonia, Biochemical

Oxygen Demand, Chemical Oxygen Demand and for odor

control in particular requirement

- chemical disinfection: to kill pathogens in influent and treated

effluents

Disadvantages

- expensive due to cost of chemicals that are used and

expenses that arise in handling the large volume of

sludge generated by chemical precipitation.

- if the treatment system is designed to reuse the treated

wastewater, the increase in concentration of particular

constituent requires due attention.

- chemical processes are generally not provided in

conventional treatment of domestic wastewater.

Chemical unit process

Biological unit processmethod which removes pollutants by biological activity

(microorganisms).

Biodegradable organic substances converted into gases that escape to the atmosphere and cell tissue are removed by the treatment.

Suspended growth process: Activated Sludge Process, Aerated Lagoon, Oxidation Pond, Aerobic and Anaerobic Digesters, etc.

Attached growth process: Trickling Filter, Rotating Biological Contactors, Bio Towers, Up-flow Filters, etc.

Treatment system

the type of combination used from the available unit

operations and processes for treatment of a particular wastewater.

Normally, a wastewater treatment plant is designed for either Preliminary Treatment System,

Primary Treatment System,

Secondary Treatment System, or

Tertiary Treatment System.

Preliminary Treatment System is mainly selected to remove floating materials and large inorganic

particulate matters of wastewater that usually cause maintenance or operational problems in primary and secondary wastewater treatments.

aka pretreatment in common treatment system.

sump and pump unit: town wastewater is usually collected in a sump or holding tank and is pumped to the higher levels of treatment units

approach channel: to convey and dampen the flow of wastewater pumped to treatment plant units

screen chamber: to remove large size of floating materials

grit chamber: to remove suspended settleable solids

skimming tank: to remove excessive oil and grease from the wastewater

Primary Treatment System remove solids and some organic materials.

In this treatment system,

-screen chamber will remove most of the large floating materials

-grit chamber will separate most of the heavy suspended solids

-primary sedimentation/settling tank will reduce 60%-70% of fine settleable suspended solids

In a conventional treatment plant, settleable suspended organic

matter is removed by primary treatment system in primary

sedimentation or settling tank (PST). Colloidal and soluble

organic content of wastewater is removed in secondary treatment

system.

Secondary Treatment System

aka biological treatment, because biological processes take place in this treatment.

using microorganism, primary bacteria to convert biodegradable organic matter contained in wastewater into simple substances and additional biomass.

The oxygen level in the wastewater will be changed in order to produce aerobic and anaerobic environment.

About 85% of the suspended solids and BOD can be removed by a well running plant with secondary treatment.

(BOD is used for microorganism to measure the quantities of oxygen in the oxidation process. The higher BOD of a source of sewage represents the higher the polluting power of that wastewater.)

There are many types of treatment plants are used to carry out secondary wastewater treatment. The common types in our country is oxidation pond. However, the trend is moving towards to Extended Aeration (EA), Oxidation Ditch (OD), Rotating Biological Contactors (RBC), Sequenced Batch Reactors (SBR) and Trickling Filters.

Oxidation ponds, aka lagoons/stabilization ponds,

-large & shallow ponds designed to treat wastewater through the interaction of sunlight, bacteria, and algae.

-consists of two ponds.

-oxidation pond is commonly used in the small communities in our country due to low operating and construction cost & the temperature in Malaysia is suitable for the aerobic bacteria as the bacteria can only survive in warm temperature.

Extended aeration system used in Malaysia is Fine Bubble Diffused Air Extended Aeration Systems (FBDAEA).

FBDAEA will be the trend of wastewater treatment plant in Malaysia because it does not require a large place and it is efficience as the sludge is recycled for the further treatment. Nevertheless, its maintenance cost is expensive and need technical skill to be maintained and operated.

Tertiary Treatment System

aka Advanced Treatment System

further treatment to reduce and remove the concentrations of residual impurities in the wastewater from the secondary treatment system.

The major purpose of tertiary treatment system is to reduce nitrogen and phosphates which can cause serious problems when they get into water body by enhancing the growth of algae blooms.

The tertiary treatment system is normally provided when:

1.the quality of standard treated wastewater (secondary effluent) is inappropriate for the final disposal requirement.

2.the concentration of leftover organic materials or suspended solids require further removal for specific reuse of wastewater after the secondary treatment.

3.the concentration of leftover nutrients is high for final disposal or reuse of wastewater.

Tertiary treatment is high-priced, so it is normally employed for

treatment of industrial wastewater.

Also known as green technology that the development and application of products, equipment and systems used to conserve the natural environment and resources, which minimizes and reduces the negative impact of human activities

• efficient for generations to have a good environment

Advantages

Reduce effluents and gain the opportunity to re-build soil with valuable organic matter.

Prevent diseases and retain the high environmental quality to let people gain a healthy life.

Environment-friendly, consume less energy, cause less environmental nuisance.

Produces lower amounts of excess sludge.

Able to control their odor problems effectively.

ApplicationAllows people to become less dependent on groundwater and surface water sources around the earth, can decrease the diversion of water from sensitive ecosystems.

Water resource can be reuse to reduce the impact of water scarcity and pollution.

Reduce the nutrient loads from wastewater discharges into waterways, reduce and prevent the eutrophication of the waterways(lakes and streams).

Reduce the pathogens in groundwater and surface water to improve human health.

Sustainable Treatment Types

• Lagoons/wetlands

• Anaerobic Digestion

• Soil Aquifer Treatment

Lagoons/wetlands

In wetland treatment, natural forces (chemical, physical and solar) act together to purify the wastewater, thereby achieving wastewater treatment. A series of shallow ponds act as stabilization lagoons, while water hyacinth or duckweed acts to accumulate heavy metals. Multiple forms of bacteria, plankton and algae act to further purify the water.

Advantages of wetland treatment

It is mechanized treatment systems.

Allows for total resource recovery.

Considered as a low-cost technology if sufficient, non-arable land is available.

Disadvantages of wetland treatment

Affected by the climate.

Some locations may make it unsustainable.

Mechanical problems may include clogging with sprinkler and drip irrigation systems.

High demand for large area of arable, flat land.

Existing significant odor problems.

Anaerobic Digestion

Anaerobic bacteria degrade organic materials in the absence of oxygen and produce methane and carbon dioxide. The methane can be reused as an alternative energy source (biogas).

Advantages of Anaerobic Digestion

No, or very low energy demand.

Production of valuable energy in the form of methane.

Low investment costs and low space requirement.

Applicable at small as well as large scale.

Disadvantages Advantages of Anaerobic Digestion

Low production of excess sludge.

Low nitrogen and phosphorus requirements.

High treatment efficiencies.

Effluents contain valuable fertilizers (ammonium salts).

Soil Aquifer Treatment

SAT (soil aquifer treatment) is a geo purification system where partially treated sewage effluent artificially recharges the aquifers and then withdrawn for future use. By recharging through unsaturated soil layers, the effluent achieves additional purification before it is mixed with the natural groundwater.

Advantages of Soil Aquifer Treatment

Cost is lower.

Remove pathogen efficiently

Operation is not highly technical

Breaks the pipe-to-pipe connection of directly reusing treated wastewater from a treatment plant.

Disadvantages of Soil Aquifer Treatment

Can change the soil and groundwater hydrological properties.

Requires a big area for the infiltration basin.

• capital city of Finland• contains more than half a million residents and located at Baltic Sea.• generate a total of 100 million cubic metres of wastewater per year• all the wastewater will be treated by one wastewater treatment plant which is Viikinmäki

largest WWTP in the Nordic countries

treats about 270 000 cubic meters of daily flow of wastewater

an average of 100 millions cubic meters of wastewater each year

was taken into use in year 1994 and it has been updated twice

year 2004, tertiary filter was added

actived sludgePhysical Process

Biological + Chemical Process

Denitrification-nitrification

• 95% of phosphorous, 90% nitrogen are removed

• 10 millions m³/y biogas 16 GWh electricity , 26 GWh thermal energy

• 55% self-sufficient in terms of electricity

• 60,000 tonnes of dried waste sludge per year

sewer tunnel system

on-line weather radar information

Sofia, BulgariaSofia, Bulgaria

Degree of Treatment Treatment Methods Viikinmäki WWTP

Kubratovo WWTP

Jelutong STP

Preliminary Treatment

Screening (Bar, Coarse, Fine) √ √ √

Grit removal & Grease Tank √ √ √

Pre-aeration Tanks √ √

Primary Mixing √ √ √

Treatment Primary Tanks/ Clarifiers √ √ √

Secondary Treatment

Acivated Sludge √ √

Extended Aeration √

Biological Aerated Filter √

Sequential Batch Reactors √

Secondary Tank √ √

Tertiary Treatment

Filtration √

Anaerobic Digestion √

Methane Tanks √ √

Combined Heat and Power engine √ √

Nitrogen and Phosphorus removal √ √ √

Viikinmäki

WWTP

Kubratovo

WWTP

Jelutong STP

Energy Efficient

Cost for electrical energy

Main Process of WWTP

Activated Sludge Cogeneration

Sequential Batch

Reactor

Low Normal High

Low quality of treated water and content of Low quality of treated water and content of phosphorus and nitrogen is highphosphorus and nitrogen is high

Insufficient sludge to be recycledInsufficient sludge to be recycled

≥ Training must be provided to all employees such as operators and supervisors

≥ Benefits for workers must be provided≥ Seminars and workshops can be organized and encourage

generation to participate≥ General knowledge about green technology must be promoted≥ Recycled resources and renewable materials can be used for

renovation and reconstruction

≥Normal operation of wastewater treatment ≥Installation of ultra-violet treatment facility ≥Complement of CHP engine ≥By using solar energy