Aeration Tank

Aeration tank is the major of the wastewater treatment structure. Treatment of wastewater using aeration equipment also called secondary treatment. Design of aeration tank absolutely refer to incoming load to the tank.

Aeration tank refers to several design for the activated sludge treatment type. A few secondary treatment tank are listed as below:

1. Extended aeration
2. Oxidation ditch
3. Batch reactor

For extended aeration tank, there are a few mutation where the process actually holding same concept such as:

1. Loyal extended aeration (LEA) - the word "loyal" refers to the designers or the manufacturer of the tank and the tank made from fibers.
2. Hi-Kleen - Normally known as a package plant where the whole structure from equilization tank, aeration tank and clarifier were ready made (fabricate in factory) from fiber or any suitable material.

The manufacturer are significantly using the same procedure in designing the treatment process, whereby the name normally to show to market about their company.

For batch reactor, few mutation of how the treatment stage are arrange prior completion of wastewater treatment process. Batch reactor means, a bulk/volume of wastewater be treated in the same tank. Batch reactor doesn't need clarifier during sedimentation stage. There are significant stage in the batch reactor includes:

1. Aeration stage
2. Settling/Sediment stage
3. Decanting/remove clean water stage

Best arrangement from the stage means reduction of expenditure during STP development/construction. On the other side, the operator will also need extra expertise in order to adapt this situation. The criticality scoring will increase as the situation will increase risk of releasing failed FE to the natural receivers. A few type of arrangement will also produce a few names such as:

1. IDEA - Intermittent Decanting Extended Aeration - become more popular in recent years.
2. IDEAL - Intermittent Decanting Extended Aerated Lagoon.
3. SBR - Sequencing Batch Reactor -most popular arragement in Malaysia because of the capabilty of existing designers and STP operator. (more easy than other 'batch' treatment process)

Malaysians Guidelines STP Developers

PART 1

General Planning Approval Requirement

The application procedures for sewage treatment plant approval shall follow the requirement given in volume 2 of these guidelines. In general, the application for approval of a treatment plant shall include:

• Sufficient land area for the sewage treatment plant plus additional area to allow for extension to the plant, where necessary.
• Buffer zones
• The location of the sewage treatment plant in relation to the reminder of the system. Sufficient topographic features shall be included to indicate its location in relation to stream and the point of discharge of treated effluent.
• Schematic flow diagrams showing utility systems serving the plant processes and the flow through various plant units.
• Piping, including any arrangements for by-passing individual units. The direction of flow through pipes shall also be shown.
• Hydraulic profiles showing the flow of sewage, supernatant liquor, and sludge
• Location, dimensions and elevations of all existing and proposed plant facilities
• Point of discharge of treated effluent (effluent outfall) and the elevations of high and low water level of the body of water to which the plant effluent is to be discharged.
• Type, size, features and operating capacity of all pumps, blowers, motors and other mechanical devices together with manufacturer catalogues.
• Minimum, average and maximum flows, velocities and top water level in profiles.
• Accessibility, landscaping and fencing
• Flow measurement facilities
• Materials, dimensions and specifications.
• Ground conditions including levels, type, groundwater level and safe bearing pressure of foundation.
• Details of foundation design.
• All other component parts of the sewage treatment plant.
• A technical report, which covers the ‘whole life’ cost evaluation of the plant.
• Presentation requirements, process and instrumentation diagram, and mass balances.
• Detailed drawings that are clear and legible and of standard format.
• Detailed information on operation and maintenance

Accident Fire and Pollution?

Looking at the smoke, you know what is happening to the environment.

This called an accidential pollution. Same like hazard spill at sea, factory or work place.

There is requirement for emergency requirement (ERP) in controlling such as hazards from above mention sources.

This accident happen during gun battle between drug dealers and police at Rio de Janeiro. Environment maybe doesn't like so critical to control such these accidential fire. But maybe, fine maybe increase to the dealer because of polluting.

ERP for accidential during gengstrism demolishment maybe needed in order to safe our environment.

Equilization Tank

Tank which consist of transfer pump and aerator. Construction of equilization tank may useful to balance treatment intake in the aeration tank. It will also useful in contolling volume of water to be treated in the aeration tank. As such, equilization tank is very important in optimizing treatment process at downstream i.e if water in the aeration tank reach its volume, feed pump will stop feeding the aeration tank while the incoming water will simultaneously accumulated/be in equilization tank before next coming volume.

Like continuos treatment such as extended aeration (EA), Equilization tank will be a buffle tank for the aeration tank during surge flow. Surge flow in treatment process may cause stability of treatment process like 'over' flowing of MLSS which means, the depletion of suspended's food digestor.

Overflowing of digestor to FE will also cause unwanted bacteria (filamentous bacteria) to grow in treatment tank, hence create hard conditions during settlement process.

Guideline by Malaysian authority during wastewater plant construction shows that, construction of equilization tank will subsequently reduce aeration tank size by specific ratio.

Equipment Involve in Grease Trap/Tank

As I said earlier, common grease tank located after grit tank. Saturated fat will be accumulated on top/surface of water. You will the accumulation in yellow color. The accumulation need to be removed to makesure optimization for downstream treatment process.

Removal equipment is called scum/oil/fat skimmer. Two type of scum skimmer normally seen in Sewage Treatment Plant (STP) which are pump/motor driven type and airlift driven type. The suction produce during its operation will skim out floating fat and drive the product to drying bed or dewatering unit before it can be dumped outside. Picture of equipment were as below:

Motor driven scum skimmer

Airlift driven scum skimmer

Problem may appear with these equipment are bloockage due to improper rugs (normally plastic and diapers/pad) screening at earlier stage and broken of suction pipe and etc.

Equipment in Grit Trap (Tank)

Normally, grit tank will be equipped with grit pump, to remove bottom's settled grit. For a big construction of sewage water treatment, the removal equipment may use airlift system to remove bottom product. Airlift system is a principal system that involve pressure gradient in a pipe. The design of airlift were illustrated as below:

Grit and Grease Trap

Grit and grease trap were always a combination. Grit are mentioned as sand, samll stone, egg shell or any small settleable in the grit trap. Grease are mentioned as oil, fat which is normally in solid shape in wastewater. Domestic water in Malaysia are very rich with these kind of organic/oleo contaminat because the culture of cooking.

Grit must be trapped and prevented to enter aeration tank (secondary treatment) because later it will interrupt downstream treatment process. It will also enhance into mechanical failure especially for diffuser inside the aeration tank. The grit also will deposit and accumulated in the aeration tank which will decrease tank depth for long term. As the consequences, surge loading or incresing loading to treatment plant will later damage the treatment process although the plant is planned and constructed based on peak factor flow.

Logically, grit chamber/trap will be constructed prior grease chamber/trap. The reason is, escaped grit hopefully will settle in grease chamber likely grease chamber will be a secondary protection to ensure grit is prevented to enter aeration tank. The grit will be managed for disposal.

Grit chamber will be equipped with either grit pump or airlift suction to remove settleable grit at bottom grit tank/chamber. Grease chamber will be equipped with surface scrapper or scum skimmer, which the equipment will remove floating material in the grease tank. The output from these equipment will also be managed dried (normally using drying bed) and disposed off.

Grease must be prevented to enter aeration tank
1) to ensure compliance of final effluent,
2) to ensure sufficient oxygen requirement for biological growth and activity inside aeration tank (to degrade oil will require more oxygen than other organic material).
3) Failure to treat the oil will increase COD and O&G paramater in FE.
4) To maximise power usage especially for aeration equipment.

Grease that removed from the grease chamber normally will create foul odour. This area is the biggest contributor to public complaint due to foul smell.

Screening (Pre-treatment)

Sewage which enters STP from sewage network will combine at incoming sump. Term "wet well" normally used by plant operator to describe the condition of wet area. As the water come in, the flow will be screening for those big/ unwanted material such as stick, wood, diapers, plastic, rags, stone, bottle, clothes, underwear, debris and steel to be removed.

Size of screen for primary is normally 15-20mm bar to bar. It is either static or mechanical screen. For a bigger plant, mechanical screen is the most important however, static screen will be provided in case of mechanical screen failure. Like a small plant (PE<500), static screen is more preferred.

Material of construction to be used for screen is either stainless steel or mild steel. Most plant operator likes to choose mild steel rather stainless steel because it’s more cheaper and low theft frequency. However, stainless steel is last longer.

Purposes for installation are:
1. To prevent loses or faulty to delivery pump (normally called RSP or Raw Sewage Pump)
2. To enhance downstream treatment process
3. To prevent loses to other mechanical equipment and installation
4. To ensure better clarifier look. It is also image of the STP which relevant to operator efficiency.

Introduction of Treatment Plant

Sewage wastewater are categorized as domestic wastewater. In Malaysia, there are several method to treat sewage water with range from non-mechanized method until fully mechanized method.

Sewage characteristic normally determined by following parameter especially Biochemical Oxygen Demand(BOD) and Chemical Oxygen Demand(COD). As Sewage treatment plant operator in Malaysia, normal BOD value are ranging from 50mg/l to 250mg/l.

As the BOD is lower in most of local Malaysia is about (50mg/l to 100mg/l) likely due to Malaysian lifestyle.

1. Average Malaysian taking bath twice a day.
2. Water from kitchen connected to sewer
3. Due local season especially heavy rain and etc.

Recycled Lubricant Oil

Hi..

When you are servicing your vehicle, have you see the mechanic take a small vacuum pump to suck the oil engine? Where they actually place the used lubricant oil? Is that place in a drum, or dump it easily? All that question or more should play in our mind..

If you search on wikipedia, it mention about the function of lubricant oil and it can be summarize as follow:
1) Is an oil used for lubrication of various internal combustion engine
2) Motor oil also cleans
3) inhibits corrosion
4) improves sealing
5)Cool the engine by carrying heat away from the moving parts.

Most of engine oil are produce from derived petroleum which contain of hydrocarbon.

Us EPA has define engine oil must be managed under hazardous waste when it is disposed of. So that, by spilling it to the environment, it can pose threat to us.

Have you heard about additives that have been used to the used engine oil? For your knowledge, the additives is meant for changing the value of it viscosity so that, it suit to standard lubricating oil. The value that determine by SAE for good lubricating oil is between 40 to 400 according to their Viscosity Index.

By inventing additives for lubricant oil, we should make money and actually we are saving our environment.

But if no additives will used, we will damage our engine, and damage our air by releasing excessive smoke, and you know what is inside the smoke.