GO GREEN

3. WATER RECYCLE SYSTEM

Wastewater from the factory is gravitated to a rotary screen. Operation of the screen is continuous whenever there is wastewater production.

The rotary screen is designed to remove rag and fine solids greater than 0.5 mm particle size. Rag and solids removed by the screen are collected in a strainer basket which requires regular emptying whenever it is full

ROTARY SCREEN

The influent sump functions as a pump station for the transfer of screened wastewater to a balance tank by means of a set of submersible influent pumps controlled automatically by a set of high and low level floats. Another high level float sets off sound alarm if water level rises to platform level due to pump failure.

INFLUENT SUMP

BALANCE TANKThe balance tank is designed with an hydraulic retention time of over 4 hours, sufficiently large for dampening load variations that occurred during the period. Too high a load variation may cause process instability in chemical and biological treatment, causing poor performance in effluent quality

Wastewater from the balance tank is pumped to the coagulation tank by a pair of submersible feed pumps controlled automatically by a set of high and low level floats.

In the coagulation tank, wastewater is mixed rapidly with the coagulant, PAC by means of air via an air Spurger to produce chemical aggregates. Flocculation with the aid of polymer is carried out in a subsequent tank with gentle mixing also by aeration. Vigorous aeration should be avoided to prevent destruction of chemical flocks by shearing.

COAGULATION AND FLOCCULATION TANKS

The functions of the primary clarifier are :

(i) To allow suspended and flocculated solids to settle to the bottom of the clarifier for subsequent removal by a primary sludge pump intermittently (3 min/hour) to a sludge holding tank. Solids removal is facilitated by a continuously rotating bottom scrapper which scraps settled solids to a small hopper located at the base near the centre of the tank. The sludge draw-off pipe is located at the bottom of the hopper.

PRIMARY CLARIFIER

(ii) To remove grease, scum or any floating material by means of a continuously rotating surface scrapper to a sludge holding tank via a scum trough.

The activated sludge tank is designed to operate at the extended aeration mode in order to provide high degree of BOD removal. As a result, the activated sludge tank is operated at a long hydraulic retention time of 18 hours with a mixed liquor suspended solids concentration of 2700 mg/l.

EXTENDED AERATION ACTIVATED SLUDGE TANK

The clarifier is designed with an up-flow velocity of 0.6 m/h. At this velocity, sludge in the wastewaterfrom activated sludge tank will settle to the bottom of clarifier, allowing clear effluent to overflow from the top of clarifier over a V-notch weir.

SECONDARY CLARIFIER

EFFLUENT TANKEffluent tank is used as a transfer tank for biologically treated wastewater to sand and activated carbon filters respectively.

The transfer is carried out by an effluent transfer pump. The pump is activated automatically whenever water level in the water tower is low

Excess wastewater which is not being recycled flows by gravity to an effluent discharge drain to disposal.

CHEMICAL DOSING TANKS Chemical dosing tanks for alkali, coagulant, flocculant, nutrients and polymer are each equipped with a mixer, dosing pump (0-120 l/h, 3.5 bar), and on-line water supply.

For the preparation of alkali dosing solution of sodium hydroxide of 20%, concentrated solution of 40% NaOH can be purchased from chemical suppliers, and diluted 1:1 ratio.

For coagulant preparation, liquid polyaluminium chloride (PAC) can be purchased at 12% solution and transferred directly to the dosing tank without further dilution required. Alternatively powder PAC (30%) may be used and made up to a 12% solution in the dosing tank.

Sludge holding tank A receives primary sludge from the bottom of primary clarifier.

SLUDGE HOLDING TANK A

Sludge holding tank B receives surface scum from primary and secondary clarifiers, waste activated sludge from RAS tank, and backwash from sand and activated carbon filters.

SLUDGE HOLDING TANK B

SLUDGE DEWATERING

Sludge dewatering is carried out by transferring the sludge in a sludge holding tank to a belt press (1500 mm width belt) via a pre-dewatering drum. The transfer is carried out by the coupling of sludge transfer pump with a variable speed screw pump (@6-30 m3/h). Polymer addition is made to an in-line mixing loop in which sludge and polymer are mixed before entering pre-dewatering drum.

SAND, ACTIVATED CARBON AND RESIN FILTERS

2 sets of Sand filter is used for removing residual suspended solids from treated effluent prior to activated carbon filter

Group A Group B

Activated carbon filter is used for removing residual color from treated effluent such that the final effluent is suitable for reuse.

SAND, ACTIVATED CARBON AND RESIN FILTERS

Resin filter is used for removing toxic ions such as mercury arsenic and many others.

SAND, ACTIVATED CARBON AND RESIN FILTERS

NEW UF SYSTEM

The Disk-Plate UF Membrane, the processing unit may remove in the water the suspension, the colloid material, the silt, the oil class, the microorganism and metabolism stickiness material. For guaranteed that will enter water quality of the RO processing unit not to fouling and adjusts the RO recovery to avoid the scaling. The system is completely automatic operation by PLC control.

The water recovery system use UF and RO to treatment the water. The product water quality may reuse, water quality surpasses the pipe water to be possible to return to the wash process system reuse again or to return to the original water treating equipment (Conductivity <100μs/cm，Hardness < 2ppm as CaCO3).

NEW UF SYSTEM

NCM Innovative Disk-Plate UF moduleAdvantage：easy clean, stable product quality, low operating pressureDimension：ψ315 m/m，Space：7 m/m

NEW UF SYSTEM

Advantage of NCM’s Water Recycle System

1.The UF module thin film filtered water system, may suit the different situation, the high turbidity surface water, the dirt, the wastewater pre-treatment system use。

2.Provides the completely automatic on-line clean function, increases UF system's service life 。

3.The disk-plate type UF module, may reduce membrane fouling, increases the filtration effect 。

NEW UF SYSTEM

Disk Plate UF Module

Container x 2sets

Raw Water (Waste Water)

Reverse Osmosis Water Systems

Reverse Osmosis Water SystemsReverse Osmosis Water System (RO System) is a filtration method that removes many types of large molecules andions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be "selective," this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as the solvent) to pass freely.

Reverse osmosis is most commonly known for its use in drinking water purification from seawater, removing the salt and othersubstances from the water molecules. This is the reverse of the normal osmosis process, in which the solvent naturally moves from an area of low solute concentration, through a membrane, to an area of high solute concentration. The movement of a pure solvent to equalize solute concentrations on each side of a membrane generates a pressure and this is the "osmotic pressure." Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis.

The process is similar to membrane filtration. However, there are key differences between reverse osmosis and filtration. The predominant removal mechanism in membrane filtration is straining, or size exclusion, so the process can theoretically achieve perfect exclusion of particles regardless of operational parameters such as influent pressure and concentration. Reverse osmosis, however, involves a diffusive mechanism so that separation efficiency is dependent on solute concentration, pressure, and water flux rate

Applications

Water and wastewater purification

Rain water collected from storm drains is purified with reverse osmosis water processors and used for landscape irrigation and industrial cooling in Los Angeles and other cities, as a solution to the problem of water shortages.

In industry, reverse osmosis removes minerals from boiler water at power plants. The water is boiled and condensed repeatedly. It must be as pure as possible so that it does not leave deposits on the machinery or cause corrosion. The deposits inside or outside the boiler tubes may result in under-performance of the boiler, bringing down its efficiency and resulting in poor steam production, hence poor power production at turbine.

It is also used to clean effluent and brackish groundwater. The effluent in larger volumes (more than 500 cu. meter per day) should be treated in an effluent treatment plant first, and then the clear effluent is subjected to reverse osmosis system. Treatment cost is reduced significantly and membrane life of the RO system is increased.

The process of reverse osmosis can be used for the production of de-ionized water.In 2002, Singapore announced that a process named NEW water would be a significant part of its future water plans. It involves using reverse osmosis to treat domestic wastewater before discharging the NEW water back into the reservoirs.

PretreatmentPretreatment is important when working with RO and nano-filtration (NF) membranes due to the nature of their spiral wound design. The material is engineered in such a fashion as to allow only one-way flow through the system. As such, the spiral wound design does not allow for back-pulsing with water or air agitation to scour its surface and remove solids. Since accumulated material cannot be removed from the membrane surface systems, they are highly susceptible to fouling (loss of production capacity). Therefore, pretreatment is a necessity for any RO or NF system. Pretreatment in SWRO systems has four major components:

* Screening of solids: Solids within the water must be removed and the water treated to prevent fouling of the membranes by fine particle or biological growth, and reduce the risk of damage to high-pressure pump components.

* Cartridge filtration: Generally, string-wound polypropylene filters are used to remove particles between 1 - 5 micro-meters.

* Dosing: Oxidizing biocides, such as chlorine, are added to kill bacteria, followed by bisulfate dosing to deactivate the chlorine, which can destroy a thin-film composite membrane. There are also bio-fouling inhibitors, which kill bacteria, but simply prevent them from growing slime on the membrane surface and plant walls.

* Pre-filtration pH adjustment: If the pH, hardness and the alkalinity in the feedwater result in a scaling tendency when they are concentrated in the reject stream, acid is dosed to maintain carbonates in their soluble carbonic acid form.

CO3-2 + H3O+ = HCO3- + H2OHCO3- + H3O+ = H2CO3 + H2O

* Carbonic acid cannot combine with calcium to form calcium carbonate scale. Calcium carbonate scaling tendency is estimated using theLangelier saturation index. Adding too much sulfuric acid to control carbonate scales may result in calcium sulfate, barium sulfate or strontium sulfate scale formation on the RO membrane.

* Prefiltration antiscalants: Scale inhibitors (also known as antiscalants) prevent formation of all scales compared to acid, which can only prevent formation of calcium carbonate and calcium phosphate scales. In addition to inhibiting carbonate and phosphate scales, antiscalants inhibit sulfate and fluoride scales, disperse colloids and metal oxides, and specialty products can be to inhibit silica formation.

Remineralisation and pH adjustmentThe desalinated water is very corrosive and is "stabilized" to protect downstream pipelines and storages, usually by adding lime or caustic to prevent corrosion of concrete lined surfaces. Liming material is used to adjust pH between 5.8 and 8.1 to meet the potable water specifications, primarily for effective disinfection and for corrosion control.

DisinfectionPosttreatment consists of stabilizing the water and preparing it for distribution. Desalination processes are very effective barriers to pathogenic organisms; however, disinfection is used to ensure a "safe" water supply. Disinfection (sometimes called germicidal or bactericidal) is employed to sterilise any bacteria, protozoa and viruses that have bypassed the desalination process into the product water. Disinfection may be by means of ultraviolet radiation, using UV lamps directly on the product, or by chlorination or chloramination (chlorine and ammonia). In many countries, either chlorination or chloramination is used to provide a "residual" disinfection agent in the water supply system to protect against infection of the water supply by contamination entering the system.

Reverse Osmosis Diagram comparing other water filtration methods