Su Arıtma

Su Arıtma Hakkında Kullanılan Teknik Terimlerin Anlamlarını ve Su arıtma sektöründe duymuş olduğunuz membrane gibi sözcüklerin anlamını linmke tıklayarak görüntüleyebilirsiniz. Su Arıtma Mechanical Engineer Mechanical Sağlık Konveyör Rulosu Makina Şirketleri okumaya devam et "Su Arıtma Terimleri ve Su Arıtma Sözlüğü"

Başlıca Su Arıtma Yöntemleri Şunlardır.

Reverse Osmosis
Ultraviole 
Aktif Karbon
Su Yumuşatma
Kum Filtreli Su Arıtma Sistemi
Demineralizasyon ve saf su sistemleri

okumaya devam et "Su Arıtma Yöntemleri ve Su arıtma"

Su arıtma Sistemleri olarak web sayfamız insanlarımıza su arıtmanın ne olduğunu, su arıtma cihazlarının ne işe yaradığını, gerçekten böyle cihazlara ihtiyaç olup olmadığını anlatmak ve gerçek, doğru bilgi vermek için hazırlanmıştır. Sayfalarımız arasında su arıtma sistemleri hakkında aklınıza gelebilecek her türlü soru ve sorunların cevaplarını bulabilirsiniz. Bunun yanında problemlerinizi bizi arayarak yada e-mail atarak da iletebilirsiniz.

Su...

Hayat kaynağımız olduğu için çok önemlidir. Bilindiği gibi dünya yüzeyinin      %70'i sularla kaplıdır. Fakat sadece bunun % 3'ü kullanılabilir niteliklere sahiptir. Bu kadar az olan ve hayatımızın her aşamasında kullandığımız su, çevresel ve doğal nedenlerle her zaman istenilen koşullara uygun olmayabilir. Dünyadaki hızlı gelişmeye paralel olarak doğal su kaynakları da her geçen gün azalmakta yada kirlenmektedir.

okumaya devam et "Su Arıtma Hakkında Su arıtma Bilinmeyenleri"

Sanayi tesisleri, fabrikalar, organize sanayi bölgeleri gibi çeşitli üretim prosesleri sonucunda oluşan atıksuların arıtılması amacı ile kurmuş olduğumuz endüstriyel atıksu arıtma sistemlerimiz atıksu karakterizasyonuna göre farklılık göstermektedir.



Üretim ve sanayi tesislerinin, üretim aşamalarında gerçekleştirdikleri faaliyetler sonucunda oluşacak atıksuları, ilgili yönetmeliklerde belirtilen deşarj standartları içerisinde arıtması gerekmektedir. Endüstriyel nitelikli atıksuların arıtılması amacı ile dizayn edilen atıksu arıtma sistemleri, boyutları ve arıtma üniteleri; sanayi/sektör türü, üretim yöntemi, atıksu miktarı, atıksuyun kirlilik değerleri ve alıcı ortam türüne göre değişiklik göstermektedir. ETC, sanayi tesislerinden kaynaklanan atıksular ile ilgili olarak laboratuar şartlarında arıtılabilirlik testleri uygulamaktadır ve laboratuar ortamında yapılan çalışmaların sonucuna göre en uygun arıtma prosesini dizayn etmektedir. Endüstriyel nitelikli atıksuların arıtılması amacı ile dizayn edilen atıksu arıtma sistemleri betonarme, paket (ST 37 sac) veya CTP malzemeden imal edilebilmektedir.



okumaya devam et "Endüstriyel Atıksu Arıtma Sistemleri"

Evsel atıksu arıtma sistemleri ETC tarafından paket (çelik konstrüksiyon) veya betonarme olarak dizayn edilmektedir. Genel olarak kullanulan ekipmanlar; ızgara, atıksu besleme pompası, şamandra, blower, difüzör, air-lift veya geri devir pompası, klor dozlama pompası, elektrik kumanda panosudur. Evsel nitelikli atıksuların arıtılması amacı ile genel olarak fiziksel ve biyolojik arıtma süreçleri kullanılır.

Paket Atıksu Arıtma Sistemleri

Ostim / Ankara ’da üretimini yaptığımız paket arıtma sistemleri; evsel ve endüstriyel nitelikli atıksu oluşumunun söz konusu olduğu nüfusu az olan turistik tesisler, yazlıklar gibi yerleşim alanları ile şantiyeler, fabrikalar ve üretim tesislerinde uygulama alanı bulmaktadır. Değişken boyutlara sahip çelik tank şeklinde imal edilen paket arıtma tesisleri taşınması kolay sistemlerdir.
okumaya devam et "Evsel Atıksu Arıtma Sistemleri Evsel Atıksu Arıtma Sistemleri, Ev Tipi Atık Su Arıtma"

Su içindeki çözünmüş maddelerin çoğu iyon halindeki inorganik tuzlardır.Negatif yüklü iyonlar anyonlar olarak,pozitif yüklü iyonlar ise katyonlar olarak adlandırılır. Deiyonizasyon üniteleri, reçine kullanılarak iyon değişiminin sağlandığı ve pratik olarak su içindeki tüm iyonların alındığı sistemlerdir.
Deiyonize su,çok geniş bir kullanım alanına sahiptir. Özellikle ilaç kimyasal ve kozmetik sanayinde, elektronik endüstrisinde,su analiz laboratuarlarında,yüksek basınçlı buhar kazanlarında, tekstil endüstrisinde, matbaacılıkta, gıda sektöründe, enerji santrallerinde ve sağlık sektöründe yaygın olarak kullanılmaktadır.
okumaya devam et "Water MILL Deiyonizasyon Sistemleri"

Ters Osmoz RO

Yarı geçirgen membran kullanılarak sudan çözünmüş maddelerin arıtılması işlemidir.RO özellikle klasik arıtım sistemlerinin yetersiz kaldığı sularda (deniz suyu,iletkenliği yüksek kuyu sularında), suyun içindeki minerallerin %90-99.8 oranında giderimini sağlar.Su teknolojindeki gelişme ile beraber RO cihazları evsel ve endüstriyel uygulamalarda yaygın bir şekilde kullanılmaya başlamıştır.


Çalışma Prensibi
Reverse Osmosis sistemi çapraz akış filtrasyon prensibine göre çalışır.Bu sistemde yüksek basınç uygulanan su, membranlara doğru itilir.Membranlara doğru itilen ham suyun bir kısmı ,yüksek basıncın etkisiyle yarı geçirgen membranın karşı tarafına geçerken ,besleme tarafında kalan konsantre su membran yüzeyini süpürerek drenaja atılır.

okumaya devam et "Reverse Osmosis Üniteleri"

Su yumuşatma,suda sertliğe sebebiyet veren kalsiyum (Ca) ve magnezyum ( Mg ) iyonlarının sudan uzaklaştırlması işlemidir. Water MILL tam otomatik su yumuşatma cihazları, kalsiyum ve magnezyum iyonlarının katyonik reçine yatağından geçirilirek Sodyum iyonları ile yer değiştirmesi esasına dayanır.Böylece iyon değiştirme yöntemi ile sistemden çıkan suyun sertliği giderilmiş olur. Kapasitesi dolan sodyum bazlı katyonik reçineler zaman, debi ve çıkış suyu sertlik değerine bağlı olarak tuzlu su ile rejenere (tazeleme) edilirler.

okumaya devam et "Su Yumuşatma Sistemleri Su Yumusatma Sistemleri"

TEZGAH ALTI REVERSE OSMOSIS İÇME SUYU SİSTEMLERİ
TEZGAH ALTI 5 KADEMELİ REVERSE OSMOSIS ARITMA SİSTEMİ (R.O)
1 – KABA TORTU FİLTRESİ
Suda bulunan tortu, çamur, kum ,kir, pas, bulanıklığa sebep olan partikülleri tutar . Filtrasyon aralığı 10 mikrondur. filtre kirlendiği zaman değiştirilir. Süre sudaki kirliliğe bağlı değişir.

2- AKTİF KARBON FİLTRESİ ( 10 micron , nominal 3 micron )
Sistemin amacı suyun içerisinde tat , koku ve renk bozukluğuna sebep olan klor, zehirli ilaç , asbest, yağ ve benzeri organikleri absorbe etmektir.

3- AKTİF KARBON FİLTRESİ ( 1 micron )
Sistemin amacı suyun içerisinde tat , koku ve renk bozukluğuna sebep olan klor, zehirli ilaç , asbest , yağ ve benzeri organikleri absorbe etmektir. T.O.C ve V.O.C arıtımı sağlar ( total organic carbon ve veriable organic carbon )

4. MEMRAN FİLİTRE ( REVERSE OSMOSIS İŞLEVİNİ YAPAN FİLTRE )
Ozmoz farklı iyon derişimlerine sahip olan ve aralarında bir yarı geçirgen membran bulunan iki çözeltinin ozmik basınç vasıtasıyla iyon derişimlerinin eşitlenmesi olayıdır. Bu olayı tersine çevirmek için bir pompa ile ozmik basınçtan daha büyük bir basınç uygulandığında, yarı geçirgen olan ve üzerinde 5 Angstrom boyutunda gözenekler bulunan membran sadece saf suyu geçirirken bakteriler, pirojenler, organik maddeler, askıda katı maddeler, erimiş tuzlar, nitrit aliminyum ve ağır metalleri tutar. Reverse Osmosis dışındaki hiç bir proses tek başına sudaki bütün yabancı maddeleri R.O. veriminde arıtamaz.

okumaya devam et "Ev tipi Su arıtma Sistemleri"

Demineralizasyon bilindiği gibi suyun içinde bulunan tüm minerallerin alınması
yani H2 O ( saf su ) haline getirilmesi işlemidir.

Bu işlem çeşitli şekillerde yapılabilir ( Buharlaştırma yogunlaştırma).( Evoparasyon,) (Menbran filtre RO reverse osmos), ( iyon degiştiriciler ile DEMİNERALİZASYON )

okumaya devam et "Saf Su Arıtma Üretim Sistemleri"

Su içerisinde bulunan Bakteri,virüs,mantar gibi mikro organizmaların. Hücre yapılarını (DNA) parçalamak suretiyle etkisiz hale getiren bir cihazdır.

Yöntem olarak su içerisinde bulunan mikro organizmaların % 99' nu yok eder.

Ultraviyole (UV) cihazları gelişmiş ülkelerde olduğu gibi ülkemizde' de su ve hava ortamlarında zararlı mikro organizmaların yok edilmesi için yaygın olarak kullanılmaktadır.

İstenmeyen mikro organizmaların (UV) ışınlarına kuvvetli olarak maruz kalmaları için, yani ışın kaynağının kirlenmemesi için ön arıtmanın uygun ve dogru seçilmesi gerekmektedir.
okumaya devam et "Su Arıtma Ultraviyole Sistemleri"

Dezenfeksiyon : Hastalık yapan organizmaların seçilerek yok edilmesine verilen teknik bir terimdir, bu işlem sırasında bütün organizmalar yok edilemez. Bütün organizmaların yok edilmesine sterilizasyon adı verilir. (Sterilizasyon işlemi Ultraviyle ile yapılır)
Genel olarak Kimyasal, Fizksel ve Mekanik yöntemlerle ve radiyasyonla dezengfeksiyon yapılır
Kimyasal maddeler arasında Klor, Brom, İyod, Ozon, Fenol, Alkol; Sabun ve deterjanlar; Hidrojen peroksit ve çeşitli alkaliler ve asitler vardır.

Fiziksel yöntemler arasında, Isı ve ışık bilhassa Ultraviyole ışığıdır.

Mekanik yöntem olarak ızgara, kum tutucu, çökeltme, biyolojik tasfiye işlemleri.

Radyasyon yöntemi ise ,Kobolt 60 gibi (radyoizotop ) maddelerden çıkan gama ışınları da su ve pissuların dezenfeksiyonunda kullanılır. Fakat burada en yaygın olarak kullanılan, Klor ile dezenfeksiyon ve Ultraviyole ile strelizasyon işleminden bahsedilecektir
okumaya devam et "Su Dezenfeksiyon Yöntemleri"

Suyun, yüksek basınç uygulanarak yarı geçirgen bir menbran üzerinden geçirilip bünyesindeki çözünmüş tuzlardan, metal iyonlarından ve mikro organizmalardan fiziki olarak arındırılmasını sağlayan bir sistemdir.

Sistem çalışması esnasında %60-65 verimle çalışır (1000 litre giriş suyu 600-650 litre su üretirken 350-400 litre atık oluşur.) Çıkış suyu demineralize su (Saf Su) kalitesinde SAYILMAYACAK iletkenliktedir.
SAF SU (10 microsimens) değerin altında ifade edilir.

Bu sistem tercih edildiğinde, ön arıtmanın Mikronik Filtrasyon, Dezenfeksiyon, Aktif karbon, Yumuşatma sırasıyla olması Menbranların çalışması ve ömürleri yönünden çok büyük önem arz etmektedir.

okumaya devam et "Reverse Osmosis Ters Osmoz Su arıtma"

Su

Yaşamımızda Unuttuğumuz Ama En Az Oksijen Kadar Hayati Önemi Olan Suyun Değeri
Suyun Önemi

Bilindiği gibi, su yenilenebilir bir kaynak değildir. Bugün kullandığınız su, milyonlarca yıl önce kullanılan suyun aynısıdır. Okullarda da öğrendiğimiz gibi, dünya yüzeyinin 3/4 ‘ü sularla kaplıdır. Fakat bunun sadece yaklaşık %2,8 ‘inin taze su olduğunu biliyor musunuz? Ve dünya suyunun sadece yaklaşık %0,3 ‘ünün insan kullanımına yönelik olduğunu biliyor musunuz?

20.yy’ın son on yılı içinde, dünya nüfusu 1 milyardan fazla artış göstermiştir. Gelecek 50-90 yıl içinde ise, bu artış ikiye katlanacaktır. Ve su kaynakları ihtiyacı da artış gösterecektir. Yeraltı ve içme suyu kaynakları hayati önem taşımaktadır.

okumaya devam et "Su Arıtma Su aritma aritma sistemleri, Su arıtma Sistemleri"

NEC Semiconductors (UK) Ltd, Livingston, was formed in 1982 as part ofthe NEC Corporation and was originally assigned for assembly and testing before expanding into manufacture. The fabrication facility produces several millions chips per month and has the largest operational clean room floor area in Europe (dated 1999). NEC incorporates reclamation and reuse within its business strategy achieving IS0 14001 accreditation in December 1991. Included in the strategy is both reduced chemical consumption and waste recycling. For instance, reduction in machine bath volume and photo-resist dispensing volumes generated significant savings in hydrofluoric acid (€40 000 ($62 040)). Materials such as cardboard, paper, plastics, acids and reject silicon wafers are also recycled. For instance, the waste silicon is used in aluminium production acting as a strengthening agent for the final product.

The initial driver for water recycling was to ensure sufficient water resources at facilities where external water was limited. The experience gained at these sites has led to reclaim plants operating at sites were water is plentiful and inexpensive. In such cases the driver for reuse is to reduce operating and capital costs of water supply with the added benefits of environmental preservation and associated publicity. Reclamation at some sites has even extended to ZLD (zero liquid discharge).

The majority of the DI water required at the production facility is used in the wet bench machines in the clean room where the silicon wafers pass through at various stages during production. The wet benches consist of a concentrated acid bath, for etching, followed by a series of rinse baths. The wafers are initially lowered into the acid bath for a preset time to achieve the required etch depth. okumaya devam et "NEC Semiconductors: microelectronics wastewater reclamation"

For the purpose of comparison, water quality characteristics of estuarine water and reclaimed water are included in Table 3.2. Water quality associated with freshwater sources, such as surface water or groundwater, is dependent on the local geohydrology, but would normally be similar to reclaimed water. As shown, there are differences in the content of nutrients, organics, and salts among the water sources. Seawater has higher levels of dissolved minerals than estuarine water.

The suitability of a water source for use in recirculating water systems as compared to once-through non-contact cooling is related to water quality and water availability. High levels of dissolved minerals and/or can demand additional treatment to prevent scale formation. For example, cooling systems that rely on estuarine or seawater tend to be non-recirculating, unless it is economical to provide on-site treatment for control of dissolved solids.
okumaya devam et "Water quality comparisons"

Water used for cooling operations can come from a variety of sources including surface water (streams, lakes, or impoundments), groundwater, seawater, estuarine water, or reclaimed water. In selecting a water source, the major requirement is that an adequate supply of water is available to accomplish cooling. The water quality of the source dictates the need for pre-treatment and the feasibility of recycling the water with or without sidestream treatment. Water quality also influences the economic feasibility of using the water source for boiler feedwater or closed recirculating systems (Baron et al., 2000: Wijesingheetal., 1996). okumaya devam et "Sources of water used for cooling operations and boiler feedwater"

In industrialized nations significant quantities of water are needed for power generation and cooling applications, greatly exceeding the quantities of water used for all other purposes (Fig. 3.1). For example, in the USA thermoelectric power generation accounts for about 47% of the 5.5 x 1011 m3 of water that is consumed annually (Solley et a]., 1998). A major water use is for condenser and reactor cooling in steam-electric power plants. For power plants equipped with wet towers for steam condensation, the evaporation of water in the cooling tower can account for up to two-thirds of the total plant water use. Other applications for cooling water include air conditioning systems, food and beverage manufacture, meat and dairy industries, chemical manufacturers, and petroleum refineries (Asano and Levine, 1998).

On a global basis, it has been estimated that about 10 000 GW of new electrical generating capacity will be required by 2050 (Powicki, 2002). Fresh water is an essential resource for the production of electricity, as it is needed for high-purity steam, condensate cooling, and miscellaneous operations including dust suppression. While the net water requirements depend on the distribution of energy sources (nuclear, fossil fuel, waste-to-energy, hydropower, solar, wind, etc.), it is obvious that energy production is dependent on water availability. In addition to projected increases in energy and associated water requirements, liquid discharges from industrial water users are subjected to increasingly stringent requirements in many locations. In the future, it is likely that many thermoelectric power generation facilities will be required to comply with socalled zero liquid discharge (ZLD) requirements to meet long-term watershed protection goals, particularly in environmentally sensitive locations (Crook et al., 1994; Puckorius, 1997). It is thus important to develop more efficient approaches to management of water in the thermoelectric power industry.
okumaya devam et "The ower industry: water requirements for power generation"

Industrial cooling tower operations are susceptible to four potential water quality problems: (1) scaling, (2) biological growth, (3) fouling of the heat problems can result from any water source (fresh, reclaimed, or salt) unless appropriate preventive measures are incorporated into the cooling water system. Definitions of each cooling water quality issue are given below. Chemicals such as chlorine and chelating agents are added to prevent biofouling and inhibit mineral build-up. As the water volume is reduced through evaporation and drift, the concentration of these chemicals and their by-products increases. Cooling towers can also contain chemicals from the ambient air.

Scaling

Scaling refers to the formation of mineral deposits, usually on hot surfaces, which can compromise heat exchanger efficiency. As with dense membrane processes, calcium deposits (calcium carbonate, calcium sulphate and calcium phosphate) are the predominant form of scale. Such deposits are somewhat heterogeneous in nature (Fig. 3.12) and their accumulation on the surfaces of heat exchangers can reduce the heat transfer efficiency, causing overheating of metal and, ultimately, boiler tube failure. In addition, the presence of deposits can provide habitats for the growth of microorganisms within the cooling system. Magnesium scales (magnesium carbonate and phosphate) can cause a similar problem. Silica scales are particularly problematic, since silica is largely insoluble and forms very tenacious deposits. Silica can volatilise at the high temperatures of boiler systems and become entrained in the steam (Dyson, 2001; Troscinski and Watson, 1970; Vanderpool, 2001). As the steam cools within the turbine, the silica can crystallise on the turbine nozzles or blades leading to increased frictional resistance and reduced steam velocities. Because the deposits are not uniformly distributed, the turbine rotors become imbalanced and produce excessive vibrations. okumaya devam et "Cooling tower water quality issues"

of water entering and leaving the system. As water evaporates, dissolved
constituents and salts become more concentrated in the liquid stream. The water
quality of the recirculating stream must be controlled to prevent operational
problems such as development of deposits on heat exchanger surfaces (scaling),
corrosion, or biological fouling. To control the quality of the recirculating
stream, water is removed as blowdown water, and to compensate for loss of
water through blowdown, evaporation and drift water is added to the
recirculating stream as make-up water (Table 3.3). Drift occurs when the water
droplets become entrained in the discharge air stream: evaporation is from air
passing through the cooling water and absorbing heat and mass: blowdown is
the imposed bleed-off of water to reduce the concentration of contaminants.
Continuous blowdown is the continuous removal of water, whereas intermittent
blowdown is initiated manually or by feedback based on water quality. These
same concepts apply to management of water quality for boiler systems (Asano et
al., 1988, Burger, 1979: Kemmer, 1988: Puckorius andHess, 1991). okumaya devam et "Optimisation of water use in recirculating cooling systems"

For the purpose of comparison, water quality characteristics of estuarine water and reclaimed water are included in Table 3.2. Water quality associated with freshwater sources, such as surface water or groundwater, is dependent on the local geohydrology, but would normally be similar to reclaimed water. As shown, there are differences in the content of nutrients, organics, and salts among the water sources. Seawater has higher levels of dissolved minerals than estuarine water.

The suitability of a water source for use in recirculating water systems as compared to once-through non-contact cooling is related to water quality and water availability. High levels of dissolved minerals and/or can demand additional treatment to prevent scale formation. For example, cooling systems that rely on estuarine or seawater tend to be non-recirculating, unless it is economical to provide on-site treatment for control of dissolved solids.
okumaya devam et "Water quality comparisons"

Water used for cooling operations can come from a variety of sources including surface water (streams, lakes, or impoundments), groundwater, seawater, estuarine water, or reclaimed water. In selecting a water source, the major requirement is that an adequate supply of water is available to accomplish cooling. The water quality of the source dictates the need for pre-treatment and the feasibility of recycling the water with or without sidestream treatment. Water quality also influences the economic feasibility of using the water source for boiler feedwater or closed recirculating systems (Baron et al., 2000: Wijesingheetal., 1996). okumaya devam et "Sources of water used for cooling operations and boiler feedwater"

An integral component of thermoelectric power production is the use of boilers to vaporise water into high-purity steam that is used to drive turbines. The operating pressure of a boiler influences the heat transfer rates, with higher pressures yielding rates of over 21 kJ m-l h-l. Materials used for boilers include mild steel, copper alloys (admiralty brass or copper-nickel), or stainless steel (Kemmer, 1988). Cooling water either flows through the tubes (tubeside cooling) or through the shell and around the tubes. The two major types of boiler designs that are in widespread use include firetube and watertube systems. The firetube boilers tend to be used in boilers that generate less than 68 000 of steam per hour, whereas the watertube boilers tend to have a higher output. okumaya devam et "Boiler feedwater systems"

Thermoelectric power plants typically derive energy from heat-generating fuels, such as nuclear fuel, coal, oil, natural gas, municipal solid waste, or refusederived fuel. The heat is used to produce steam in a boiler. The steam passes through a turbine and is then condensed back to water and pumped back to the boiler to repeat the cycle. The turbine drives a generator that produces electricity. Steam turbines extract power from steam as it passes from highpressure and high-temperature conditions at the inlet to low-pressure and low-temperature conditions at the outlet. The outlet pressure is a function of the temperature of the cooling water used to absorb heat and reject it from the condenser (Asanoetal., 1988; Burger, 1979; Kemmer, 1988). The water requirements for power plants are based on providing water for cooling and water as a source of steam in boilers. Typically, higher quality water is needed for boiler feed water as compared to cooling water. In general, cooling systems function to remove excess heat from heat sources. A cooling tower acts as a heat exchanger by driving ambient air through falling water, causing some of the warmed water to evaporate, thereby dissipating heat and providing cooling. The cooler water is then circulated back to the equipment that needs cooling. In thermoelectric power plants, cooling water is used to remove heat from the turbine exhaust and condense it back to liquid prior to its return to the steam generator.
okumaya devam et "Overview of cooling water systems"

In industrialized nations significant quantities of water are needed for power generation and cooling applications, greatly exceeding the quantities of water used for all other purposes (Fig. 3.1). For example, in the USA thermoelectric power generation accounts for about 47% of the 5.5 x 1011 m3 of water that is consumed annually (Solley et a]., 1998). A major water use is for condenser and reactor cooling in steam-electric power plants. For power plants equipped with wet towers for steam condensation, the evaporation of water in the cooling tower can account for up to two-thirds of the total plant water use. Other applications for cooling water include air conditioning systems, food and beverage manufacture, meat and dairy industries, chemical manufacturers, and petroleum refineries (Asano and Levine, 1998).
okumaya devam et "Water demand by the power industry"

Key elements of process design that contribute to costs are:

e staging, e power consumption, 0 fouling and pre-treatment, and e backflushing and cleaning. Staging is of critical importance in large-scale dense membrane processes, i.e. reverse osmosis, nanofiltration and electrodialysis. Fouling is ubiquitous throughout the entire gamut of membrane technologies, but pretreatment to suppress or ameliorate fouling is only routinely practised in dense membrane processes. Backwashing is always carried out when the module design permits this, and cleaning is an essential part ofmembrane plant operation.

Staging

For most dense membrane processes the conversion of feed into product is limited either by the membrane area or the rate of extraction attainable by passage through a single module. It is for this reason that most reverse osmosis and electrodialysis technologies employ staging, the use of sequential stages to produce more product than that attainable by a single passage.

cannot normally achieve a recovery of much more than 20%, and the onset of concentration polarisation and the scaling this produces normally limits the conversion to well below this figure. It is therefore normal for them to be placed in series, with the retentate stream from one element being passed on to the feed stream of the next (Fig. 2.19). As many as eight or nine elements may be placed in a single module, and the resultant retentate flow exiting the module is then given by (fromEquation (2.3)):

where Q is the feed flow rate, 0 the conversion per element and n the number of elements per module. okumaya devam et "Membrane Process design and operation"

A membrane is only useful if it takes a form which allows water or pollutants to pass through it. The configuration of the membrane, i.e. its geometry and the way it is mounted and oriented in relation to the flow of water, is crucial in determining the overall process performance. Other practical considerations concern the way in which the membrane elements, i.e. the individual discrete membrane units themselves, are housed to produce modules, the complete vessels through which the water flows. The optimum membrane configuration is one that has the following characteristics:

(a) a high membrane area to module bulk volume ratio

(b) a high degree of turbulence for mass transfer promotion on the feed side

(c) a low energy expenditure per unit product water volume

(d) a low cost per unit membrane area

(e) a design that facilitates cleaning

(f) a design that permits modularisation.

All membrane module designs, by definition, permit modularisation (f), and this presents one of the attractive features of membrane processes per SE. However, some of the remaining listed characteristics are mutually exclusive. For example, promoting turbulence (b) results in an increase in the energy expenditure (c). Direct mechanical cleaning of the membrane (e) is only possible on comparatively low area:volume units (a) where the membrane is accessible. Such module designs inevitably increase the total cost per unit membrane area (d). Finally, it is not possible to produce a high membrane area to module bulk volume ratio without producing a unit having narrow feed channels, which will then adversely affect turbulence promotion.
okumaya devam et "Membrane configurations"

The search for new membrane materials with superior properties with respect to permeability and resistance to chemical, thermal and biological attack is ongoing. Of greatest interest is fouling resistance, and this demands the development of membranes with a low affinity to pre-identified foulants in the feedstock. The ease with which this can be achieved is to a large extent dependent on the heterogeneity of the feedwater matrix, since the membrane surface cannot be modified so as to be able to repel contaminants of different charges and hydrophobicities. In general natural foulants tend to carry a negative charge, which then demands that the membrane also carries a negative charge to repel the foulant. It should be pointed out, however, that some filters are surface modified to carry a positive charge (e.g. the Pall “Posidyne” nylonbased filter) to attract negatively charged suspended materials, but these filters are actually depth filters designed to retain particles rather than reject them. One application that has received a great deal of interest is the removal of natural organic matter (NOM) from upland surface waters for potable water production using nanofiltration membranes. NOM contains a number of different fractions of which humic acids are one. Humic acids, which contain phenolic and carboxylate functional groups, tend to be negatively charged in neutral solutions, such that a highly negatively charged membrane would be expected to repel these contaminants allowing operation at higher fluxes than would normally be attainable without fouling. This has focused attention upon highly negatively charged membranes and, in particular, blends of sulphonated poly(ether ether ketone) (SPEEK) or sulphonated poly(ether ether sulphone) (SPEES) with polysulphone or polyethersulphone, respectively (Bowen et al., 2001; Knoell et al., 1999). These membranes are likely to be commercialised within the next five years. okumaya devam et "Recent developments. membrane materials"

Membrane manufacture ostensibly concerns the production of a permeable material at a reasonable cost. The membrane cost is dependent on not only the raw material but also on the ease with which pores of the desired size or size distribution can be introduced. This can vary considerably from one material to the next according to the method used and the corresponding precision of the pore size distribution (or degree of isoporosity).

The range of available membrane materials employed in water and wastewater treatment is very broad, and they vary rather more widely in chemical composition than in bulk morphology. Membranes can be produced by stretching, sub-atomic particle bombardment combined with etching and, in the case of ceramic materials, sintering (Table 2.2). These membranes are formed by the pressing and sintering of fine powders onto a pre-prepared porous support, which can produce pore diameters down to around 2 pm, followed by sol-gel processes to produce successive deposits of progressively finer porous layers down to a minimum pore size of around 3 nm. Ceramic nanofiltration membranes, however, have only recently arrived in the marketplace. The production process tends to be very expensive if a highly selective membrane layer of even thickness and narrow pore size distribution is to be produced. The cost of microfiltration or ultrafiltration membranes derived from titanium and/or zirconium usually exceeds $1000 per m2, although there appears to be some progress in producing low-cost ceramic membranes. At the opposite end of the spectrum are simple, homogenous polymeric membranes produced by extrusion (stretching) of partially crystalline sheets perpendicular to the orientation of the crystallites, possibly with the assistance of a fibrulating agent. Such materials cost less than $1 per m2 to produce, since the process can be made continuous, and the cost of the membrane module is then determined almost entirely by the module fabrication cost. However, such membranes are limited in their permeability, isoporosity and mechanical strength. okumaya devam et "Membrane materials and their manufacture"

Although membrane materials vary vastly according to chemical composition
and process type, the principal objectives in membrane manufacture are always
the same. An ideal malerial will:
have reasonable mechanical strength, 0 maintain a high throughput, and 0 be selective for the desired permeate constituent. These last two parameters are mutually counteractive, since a high degree of selectivity is normally only achievable using a membrane having small pores and thus an inherently high hydraulic resistance (or low permeability). The permeability also increases with increasing density of pores, and the overall membrane resistance is directly proportional to its thickness (in accordance with Darcy’s law). Finally, selectivity will be compromised by a broad pore size distribution. An optimum physical structure for any membrane material is thus: a high porosity.

a thin layer of material, a narrow range of pore size, and Membrane materials can be categorised as either dense or porous, and by the mechanism by which separation is actually achieved (Table 2.1). Separation by dense membranes relies to some extent on physicochemical interactions between the permeating components and the membrane material, and relate to separation processes having the highest selectivity (Fig. 2.1 ). Porous membranes, on the other hand, achieve separation mechanically by size exclusion (i.e. sieving), where the rejected material may be either dissolved or suspended depending on its size relative to that of the pore. Since some membranes exhibit properties that can be associated with more than one process type, the boundaries between the adjacent membrane processes in Fig. 2.1 are somewhat nebulous. For example, IUPAC (1985) state that the upper and lower boundary limits for mesopores, as are characteristic of a UF membrane, are 2 and 50 nm. According to Kesting (1989), howcvcr, these boundaries are at 1 and 20 nm. respectively.
okumaya devam et "Membrane structure"

There are a number of definitions of the word “membrane”, which can vary considerably in comprehensiveness and clarity. It is a very widely used term, and can mean anything from a cell wall to damp proofing material. Three definitions, arbitrarily chosen from pertinent technical literature from the last 20 years are provided below: “An intervening phase separating two phases and/or acting as an active or passive barrier to the transport of matter between phases” - the European Society of Membrane Science and Technology (now the European Membrane Society). okumaya devam et "The membrane Membrane and membrane process definition"

Membrane processes are designed to carry out physical or physicochemical separations. Although most membrane applications are water based, there also exist gas-liquid and gas-gas separation processes, although these are more recent developments and have not yet achieved widespread implementation. In terms of membrane sales, the most important application by far is hemodialysis, as carried out in kidney dialysis machines: almost half of all membrane sales are accounted for by this one application. The development of membrane-based bulk water and wastewater treatment processes, as defined in Table 1.6, is nonetheless significant, since they offer three clear advantages over conventional techniques:

1. Separation is achieved without requiring a phase change, and is therefore more energetically efficient than distillation.

2. Little or no accumulation takes place in the process which therefore operates continuously under steady-state condition without necessitating regeneration cycles, unlike adsorptive separation processes.

3. Little or no chemical addition is required, unlike conventional clarification which generally relies on the addition of chemical coagulants and flocculants.
okumaya devam et "Membrane technology"

Industry accounts for about a quarter of all water consumption, and there is hardly any industry that does not use large volumes of water (Table 1.1). Although some industries abstract water from rivers and boreholes, much of the water used by industry is taken from public water supplies, and has therefore been treated to potable quality standards. This means that it is often of better quality with respect to microbial levels but nonetheless requires further purification to reduce the mineral and organic materials content according to the specific duty to which it is to be put (Tables 1.2 and 1.3). Although water consumption has actually decreased over the last 15 years in some regions of the world (Table 1.4), the price of supply and discharge has risen substantially over the same period. According to figures for the UK, the average cost of water supply and sewerage services to unmetered customers has more than trebled in the last 15 years from €1.48 [$2.12] in 1984-85 to €4.90 [$7.94] in 1999-2000 (Water UK, 2000). In more arid regions of the world the figure is higher: between 1980 and 1995 water costs increased by more than an order of magnitude in California (Mannapperema et al., 1993). It is clearly of some cost benefit to acquire a source of water that is commensurate with the quality demanded for its end usc, without increasing freshwater demand or discharging waste to sewer. The economic viability of existing municipal effluent reclamation is then very much dependent on the match between the effluent water quality and that demanded by the duty.

A whole industry has built up around the above key concept. Pinch analysis has conventionally been employed to maximise heat transfer efficiency within an industrial process. Water pinch analysis (Baetens, 2002; Section 4.2) is simply pinch analysis based on water quality and volumes, i.e. based solely on mass rather than heat. As such, it is simply an extension of a simple water audit. On the other hand, water pinch analytical tools have not yet reached a level of sophistication where water purification unit processes can be incorporated, since the performance of such processes can rarely be reliably predicted. Volumes of water used are actually extremely dependent upon the policy of the company or the individual factory regarding water management, and in particular their housekeeping. Housekeeping relates to the way individual unit operations within the factory are conducted so as, in this instance, to limit the freshwater demand. Actual examples of demand management, reuse and recycling (Table 1.5) demonstrate that the degree of sophistication of the solution to achieve a significant cost benefit depends upon the existing state of water management. okumaya devam et "Industrial water"

The motivations for recycling of wastewater are manifold. Most often stated are those pertaining to increasing pressures on water resources. Reuse of wastewater conserves the supply of freshwater, and this presents clear advantages with respect to environmental protection. More pragmatically, wastewater reuse may result directly from legislation, which can constrain the discharge of polluted water by making this option onerous or else forbid such discharges altogether, or it may simply be favoured economically regardless of regulatory stipulations.

It is also the case that reuse itself is an emotive issue, and perhaps particularly so in the case of water. For domestic water recycling, that is recycling of water for non-contact domestic use such as toilet flushing or irrigation, public perception issues can outweigh the technical ones in terms of barriers to imposition. Key to this are the matters of ownership and identity. Studies have demonstrated that people are generally prepared to reuse water if it derives entirely from their own household, i.e. if they know where it has been. They are rather less prepared to use water if it is identified as deriving from some other source such as, for example, their neighbour’s house (Jeffrey, 2002). Curiously, the complete loss of identity, such as arises either from large-scale community schemes, and indeed from conventional water supply via municipal works and intermediate environmental water bodies such as rivers, reservoirs and aquifers, is also perceived as being acceptable.
okumaya devam et "Water reuse motivations and barriers"