The surface water in indonesia comes in various condition. It can start from a place that has a very small flow to an area with surplus water but not feasible for consumption. For all surface water, requires treatment before it can used as clean water for daily usage. The treatment used to treat the water will depend on the quality of that water itself.
Water with has high turbidity requires sedimentation of the suspended solids in the water, and water that has metal irons or manganese will require aeration before being treated. These are the small excamples on what treatments are used for treating surface water to become clear – clean water for daily use.
Up to this stage the water will be clear, but not to be used as potable water yet. In the era where everyone has known computers and internets, for sure the water treatment technology has upgrade them self to an advance stage as well.
Membranes at first were only used for labrotory purpose, now has become economically enough to be used in society. The usage of the membranes is based on the the type of the membrane as well as the usage of the product needed on the field. This range starts from a very tight pore size where even salt cannot pass (for seawater reverce osmosis), color separation for water with high color content, to the basic clean water to potable water filtration. This can all be used and adjust depending on what the purpose required.
Membrane Based on Classification
Microfiltration removes particles higher than 0,08-2 µm and operates within a range of 7-100 kPa. Microfiltration is used to remove residual suspended solids (SS), to remove bacteria in order to condition the water for effective disinfection and as a pre-treatment step for reverse osmosis. Relatively recent developments are membrane bioreactors (MBR) which combine microfiltration and a bioreactor for biological treatment
Ultrafiltration removes particles higher than 0,005-2 µm and operates within a range of 70-700kPa. Ultrafiltration is used for many of the same applications as microfiltration. Some ultrafiltration membranes have also been used to remove dissolved compounds with high molecular weight, such as proteins and carbohydrates. In addition, they are able to remove viruses and some endotoxins.
Nanofiltration is also known as “loose” RO and can reject particles smaller than 0,001 µm. Nanofiltration is used for the removal of selected dissolved constituents from wastewater. NF is primarily developed as a membrane softening process which offers an alternative to chemical softening. Likewise, nanofiltration can be used as a pre-treatment before directed reverse osmosis. The main objectives of NF pre-treatment are to minimize particulate and microbial fouling of the RO membranes by removal of turbidity and bacteria, to prevent scaling by removal of the hardness ions, to lower the operating pressure of the RO process by reducing the feed-water total dissolved solids (TDS) concentration..
Reverse Osmosis (RO)
commonly used for desalination. As well, RO is commonly used for the removal of dissolved constituents from wastewater remaining after advanced treatment with microfiltration. RO excludes ions but it requires high pressures to produce deionizer water (850-7000 kPa).
- Tubular (porous tube)
- Hollow fiber (thin hollow fiber)
- Spiral wound (flexible permeate roled up)
- Plate and frame (used for flat sheet membrane)
- Ceramic and polymeric flat sheet membranes
Hollow Fiber Nano Filtration
Hollow fiber - Nanofiltration is a new filtration technology. The pore size of the membrane reaches 1000 dalton. This pore size allows the nano molecules and molecular divalent salts pass while the organic content of dissolved or dissolved organic'll be stuck outside the membrane..
- With the hollow fiber technology; pump pressure was not high, so OPEX becomes lower.
- The system is operated without the addition of chemicals, so OPEX becomes lower too
- Because processing is done without chemicals, excess can be returned directly to the river and did not produce byproducts such as sludge
- Output quality is stable with good quality
PT Bayu Surya Bakti Construction has conducted pilot plant testing of this membrane in Siak – Riau.
Experiments conducted with water inlet and the inlet of swamp water products from conventional processing location. By testing the ability of these membranes in water on the Siak River that contains color high enough, water can turn out products that can meet drinking water standards for color and turbidity.
Recovery rate from raw water :
- With colored raw water: 50% - 60%
- Polishing, with raw water treatment products of conventional on-site: 70% - 78%
Hollow Fiber Based Flow
Outside – in flow
The water will flow through the outside and the filtered water will go through the inside of the fibers. This can happen due to the difference of the pressure. The particles that are bigger then the pore size of the membranes will stay on the outside of the membrane and will be flushed out as reject water
Inside – out
Water will flow through the inside of the membranes, and only the filtered water can pass through the membranes. Particles bigger then the pore size will be stuck inside the fibers will be flushed out as the concentrate or reject water.