Sistem Instalasi kebutuhan air untuk Rumah Sakit

Rumah sakit adalah tempat yang unik. di dalamnya terdapat orang-orang yang menginap layaknya hotel, ada orang yang bekerja layaknya di kantor, ada juga restoran dan dapur yang melayani orang yang menginap dan bekerja tadi. Lebih rumit lagi, rumah sakit ada alat-alat besar yang mendukung operasionalnya seperti genset, boiler, clarifier (pemasok air panas) dan alat-alat kesehatan seperti mesin haemodialysa, alat penguji darah dan sejumlah peralatan lain.

Karena kondisi yang unik tersebut, maka desain kebutuhan air untuk rumah sakit tidak dapat disamakan dengan desain kebutuhan air untuk hotel, hunian/residential, mal atau bangunan komersial lainnya. Desain kebutuhan air untuk rumah sakit harus dibuat unik pula berdasarkan pelbagai aktivitas rumah sakit dan orang-orang di dalamnya yang meliputi, pegawai, pasien, pengunjung dan mesin-mesin di dalamnya.

Contoh yang ekstrim untuk ini misalnya kebutuhan air untuk pasien di unit haemodialysa (cuci darah) yang membutuhkan air reverse osmosis dan steril, para pengunjung membutuhkan air bersih untuk aktivitas mereka di MCK, sementara para unit instalasi gizi membutuhkan tingkat kualitas air minum baik untuk supply pegawai atau para pasien rawat inap.

Jika didetailkan lebih jauh, maka kebutuhan air untuk rumah sakit dapat digolongkan sebagai berikut :

1. Air bersih (Permenkes 416 tentang standard air bersih) untuk MCK dan kebutuhan umum
2. Air lunak / soft water --> heat exchanger, mesin sterilisasi di CSSD, clarifier / air panas)
3. Air Reverse Osmosis yang diaplikasikan untuk :
- Air minum --> untuk instalasi gizi dan kantin / cafetaria
- Unit Haemodialysa
- steam generator di boiler dan alat CSSD
- laboratorium, biasanya ditambahkan lagi deionizer untuk lebih memurnikannya

Kenyataannya, pendirian rumah sakit tidak didasarkan atas kebutuhan tersebut. Rumah sakit baru yang didirikan biasanya hanya menggunakan filter pasir dan karbon aktif saja. Rumah sakit kemudian akan membuat instalasi air bersih parsial di unit-unit yang membutuhkan tingkat kualitas air lebih tinggi. Hal ini menyebabkan biaya lebih tinggi dan tidak efisiennya ruangan yang digunakan karena pengelola harus menyediakan tempat untuk instalasi air parsial tersebut. Belum lagi masalah estetika, karena rumah sakit modern dirancang lebih nyaman bagi para pasien dan pengunjungnya.

Untuk mendapatkan desain kebutuhan air yang efektif dan efisien baik secara budget dan luasan tempat yang dipakai sebaiknya menyarankan kepada arsitek, konsultan ME bekerja sama dengan specialis water treatment yang faham dengan kebutuhan air rumah sakit. Salah satunya bisa kontak di telpon 0856 888 1197 dengan pemilik blog ini :-)

 Jenis-jenis pengolahan limbah cair

Pengolahan limbah dapat digolongkan pada beberapa jenis meliputi: (a) sistem lumpur aktif (b) sistem trikling filter, (c) sistem RBC (Rotating Biolocal Disk), (d) sistem SBR (Sequencing Batch Reactor), (e) kolam oksidasi,(f) sistem UASB, dan (e) septik tank. Kedua sistem terakhir ini termasuk dalam kategori pengolahan limbah cair secara anaerobik.

a. sistem lumpur aktif

Sistem lumpur aktif adalah sistem pengolahan limbah dengan menggunakan biomassa sehingga menghasilkan lumpur hasil aktifitas mikroorganisme yang kemudian diendapkan. Sehingga sistem ini selalu memiliki dua proses utama yaitu adanya bioreaktor dan bak/tangki pengendapan (sedimentation tank).

Gambar 1. Bioreaktor (ditulis dengan AEROBIC TANK) dan tangki pengendapan SEDIMENTATION TANK), dua proses utama dalam sistem lumpur aktif.

Dalam tangki bioreaktor dialirkan gelembung udara (diaerasi) yang berfungsi dalam proses penguraian oleh mikroorganisme. Proses aerasi ini juga disertai pengadukan sehingga terjadi proses yang hampir sama di semua bagian bak. Suspensi biomassa dalam limbah cair yang diolah ini kemudian diteruskan ke tanki pengendapan dimana terjadi pemisahan antara biomassa dan air. Air hasil olahan ini kemudian dibuang ke lingkungan, sementara biomassa sebagian
dimasukkan kembali dalam bioreaktor dan sisanya dibuang sebagai exess sludge.

Pengolahan limbah cair dengan sistem lumpur aktif didesain dengan berbagai tujuan diantaranya : (1) penyisihan senyawa karbon (oksidasi karbon), (2) penyisihan senyawa nitrogen, (3) penyisihan fosfor dan (4) stabilisasi lumpur secara aerobik simultan.

Penyisihan senyawa karbon (organic matter) adalah proses oksidasi senyawa organik oleh mikroorganisme dibantu oksigen yang menghasilkan gas karbon dioksida. Sementara penyisihan senyawa nitrogen (eliminasi nutrien: nitrogen dan fosfor) dilakukan terutama untuk mencegah terjadinya eutrofikasi pada perairan.

Proses bioreaktor terjadi karena mikroorganisme dalam biomassa menguraikan bahan organik tersebut menjadi air, karbon dioksida dan sludge. Agar proses tersebut berjalan dengan baik maka ada beberapa kriteria yang harus dipenuhi yaitu:

• polutan dalam limbah cair harus kontak dengan
  mikroorganisme
• suplai oksigen terpenuhi
• nutnien terpenuhi
• waktu tinggal (waktu kontak) terpenuhi dan
• jumlah serta jenis biomassa

Untuk mencapai proses yang sempurna diperlukan pemenuhan kriteria seperti yang disebutkan diatas. Dengan demikian, perancangan desain awal dan operasional sistem berjalan menjadi sangat penting. Parameter yang harus diperhatikan untuk sistem lumpur aktif adalah tingkat pembebanan, konsentrasi biomassa (diukur dari Mixed Liquor Suspended Solids disingkat MLSS), konsentrasi oksigen terlarut, lama waktu aerasi, umur lumpur, dan suplai oksigen.

Sumber Bishof, 1993 dalam Dirjen IKM - Deprin, 2007

Memahami Osmosis (Keadaan Setimbang Air)

Ultrafiltrasi adalah teknologi water purifier skala menengah (middle treatment) yang berfungsi menahan atau menyaring semua partikel berukuran 0,01 - 0,5 mikron. Cara kerja Ultrafiltration mirip dengan cara kerja Reverse Osmosis. Hanya saja membran RO dapat menyaring partikel sampai ukuran 1/10.000 mikrometer. Untuk memahami cara kerja reverse osmosis kita harus memahami Osmosis, yaitu keadaan setimbang air.

Gambar 3. Membran Semipermeable memisahkan dua jenis konsentrasi larutan

Pada Gambar 3, terdapat membran semipermeable yang memisahkan dua jenis larutan yang berbeda konsentrasi. Sebelah kiri adalah air dan sebelah kanan larutan air dan sukrosa (polisakarida). Molekul-molekul air mengalir dari sebelah kiri ke sebalah kanan atau dari larutan yang kerapatannya rendah ke bagian larutan dengan kerapatan tinggi.

Karakteristik Membran : Mikon Filter, Ultrafiltration & Reverse Osmosis

Teknologi filtrasi air dewasa ini sudah menjadi keharusan dan kebutuhan semua orang. Setiap pendirian bangunan baru baik itu rumah sakit, residensial, industri maupun bangunan komersial lainnya pasti dilengkapi dengan filter air. Hampir tidak ada bangunan yang membutuhkan air bersih di Jakarta tidak menggunakan filter, apalagi jika sumber airnya didapat dari air tanah.

Namun sayangnya filter yang dibuat itu hanya terbatas pada filter penghilang kekeruhan (turbidity removal) dan filter penghilang aktivitas organik (organic removal) yang kita kenal sebagai sand & carbon filter. Fitrasi dengan sand & carbon filter adalah filtrasi tingkat pertama dimana jika requirement air yang dibutuhkan lebih dari itu, maka perlu dilakukan treatment lanjutan.

Gambar 1. Diagram ukuran membran

Salah satu tingkat lanjut dari treatment air adalah mengurangi kadar partikel zat padat dalam air. Penguranan ini memerlukan filter yang dapat menahan ukuran partikel yang diameternya (jika diandaikan bahwa partikel itu berbentuk bola) lebih besar dari lubang filter seperti yang tampak pada Gambar 1. Pada kenyataannya membran yang dipakai oleh masyarakat umum adalah filter dengan ukuran mikrometer/mikron saja tepatnya ukuran 0,1 sampai 10 mikron (1 mikrometer = 1/1.000.000.000 meter).

Mikron filter itu seperti dalam gambar hanya dapat menahan cairan yang mengandung darah, minyak dan bakteri. Padahal syarat air untuk digunakan di rumah sakit misalnya lebih tinggi daripada itu. Misalnya saja untuk air Haemodialyse & laboratorium, dibutuhkan hanya partikel air saja dengan kandungan zat padat terlarut (TDS) tidak melebihi 4 ppm. Artinya dibutuhkan membran atau selaput yang dapat menahan partikel-partikel yang ukurannya lebih kecil lagi.

Gambar 2. Karasteristik Membran dalam menangkal partikel & mikroorganisme

Pada gambar 2, kita dapat melihat karakteristik membran secara kasar. Mikron filter dapat menahan atau menyaring sebagian besar virus, tetapi meloloskan bakteri suspended solid (zat padat tidak terlarut). Sedangkan Ultrafiltration dapat meloloskan hampir semua jenis mikroorganisme baik bakteri maupun virus. tetapi masih meloloskan partikel-partikel gula dan ion baik valensi satu maupun lebih. Sedangkan Reverse Osmosis hanya meloloskan partikel air saja (H2O).

Ultraviolet light for water treatment

Drinking water is essential for life, but is a valuable and scarce commodity. Lessthan 0.01% of the planet‘s 1.4 billion cubic kilometers of water is easily accessiblefreshwater. Several global mega-trends, like population growth, urbanization andclimate change, are driving water scarcity and public concerns on water quality.According to the World Health Organization (WHO), more than two million people –many of them children – die each year of diarrhoeal diseases that are caused bywater borne pathogens. Access to safe water is one of the big challenges of ourtimes and ultraviolet light for water treatment has become an essential technologyto meet it.



Drinking water is essential for life, but is a valuable and scarce commodity. Lessthan 0.01% of the planet‘s 1.4 billion cubic kilometers of water is easily accessiblefreshwater. Several global mega-trends, like population growth, urbanization andclimate change, are driving water scarcity and public concerns on water quality.According to the World Health Organization (WHO), more than two million people –many of them children – die each year of diarrhoeal diseases that are caused bywater borne pathogens. Access to safe water is one of the big challenges of ourtimes and ultraviolet light for water treatment has become an essential technologyto meet it.

UV Water Disinfection – a Safe Method and Economic AlternativeThe first UV water decontamination was installed in Paris, France as early as 1910.Quartz glass lamps – a development that goes back to the chief developer at Heraeus,Richard Küch (1860 – 1915) - are still used today, but modern high-tech UV lampsand their early predecessors are worlds apart. Today’s UV disinfection is a wellestablishedtechnology. The method is very safe and based on profound scientificknowledge. The real challenge today is to further increase the efficiency and servicelife of the lamps.

Contaminated water can be treated with high energy UV radiation which inactivatesviruses or micro-organisms such as bacteria, yeasts, fungi or even parasites. UV watertreatment has several benefits over other disinfection processes, notably chemicalssuch as chlorine and ozone, or filtration. It does not use chemicals, which makesit environmentally friendly.

The method is not pH-dependent and does not affectthe water’s qualities, like taste, odor or color. Disinfection byproducts (DBPs) withcarcinogenic or toxic effects are not formed. An all-important advantage is the fact,that pathogens cannot build any resistance to UV light. Thus, UV inactivates evenGiardia and the chlorine-resistant Cryptosporidia. UV disinfection has low overallcapital and operating costs, and is easy to maintain and operate.

Removal of Harmful Chemicals – Advanced Oxidation with UV Micropollutants, which include such chemicals as endocrine disrupting compounds,pharmaceuticals and personal-care-products have come into public focus in recentyears and are a serious threat for drinking water quality. In order to decompose thegenerally complex structures (e.g. of steroids or antibiotics) UV radiation is combinedwith powerful chemical oxidants such as ozone or hydrogen peroxide. A processknown as advanced oxidation process (AOP).

Fertilizers, herbicides and pesticidesfrom agriculture are other examples of micropollutants that can be successfullytreated with this method, as is shown in Andijk at Holland’s largest drinking waterreservoir Ijsselmeer.

Spectrum

Ultraviolet radiation covers the wavelength range from 100 to 380 nanometers.The disinfection process uses wavelengths in the UVC range from 240 to 280nanometers, while the oxidation process uses the wavelengths down into the VUVrange below 200 nanometers.

UVC light for technical applications is usually generated by mercury lamps becauseof their high efficiency in terms of electrical energy conversion into UVC light.Commonly, there are two types of mercury lamps used: low pressure and mediumpressure lamps.

Sketch of a typical low
pressure lamp

Sketch of a typical medium
pressure lamp

Low Pressure Lamps
A low pressure lamp comprises of a quartz tube with pinched filaments, is filled withrare gas (some mbar) and mercury or amalgam. The filaments are coated with emitterpaste that facilitates escaping electrons from the filament. A voltage applied acrossthe lamp provides an electrical discharge. The power density of the discharge is low,therefore only a small portion of mercury is evaporated and enters the gas phase. Therare gas acts as a buffer gas and is necessary for maintaining the electrical discharge.Mercury atoms are ionized and excited in the discharge by electron impact. Excitedatoms emit very effectively photons with two wavelengths: 254 nm and 185 nm inthe UV range (often called spectral lines). 185 nm emission can be filtered out bychoosing quartz of suitable transmittance.

Disinfection process

The 254 nm emission is well absorbed by DNA ofall microorganisms and viruses. This absorptionleads to a destruction of the genetic structureof DNA and inhibits the transcription of itsinformation. The microorganisms and viruses arebiologically inactivated, thus 254 nm emission issuitable for disinfection purposes.

Drinking and Process Water Treatment

UV is applied in water treatment prior to consumption e.g. for drinking and processwater or afterwards in sewage plants to treat the waste water. Generally, watertreatment is performed in several stages. Usually UV water treatment is used in thesecond-to-last or last stage depending on the specific application (see chapter 3).Stages of water treatment depend on individual water quality and vary from case to case.

UV is applied in water treatment prior to consumption e.g. for drinking and processwater or afterwards in sewage plants to treat the waste water. Generally, watertreatment is performed in several stages. Usually UV water treatment is used in thesecond-to-last or last stage depending on the specific application (see chapter 3).Stages of water treatment depend on individual water quality and vary from case to case.

UV water treatment equipment can generally be classified into two groups:n closed systems for drinking and process water treatmentn open channel configuration for wastewater treatment in sewage plants.






Closed reactor systems are used for drinking and process water treatment, in order to avoid any recontamination. For drinking water, a fluence of 400 J/m² was established as a minimum requirement for effective disinfection. This minimum UVC fluence corresponds to DVGW, ÖNorm and NSF ANSI standard (class A UV system). Please refer to chapter 9 for further information.


UV water treatment is a simple, economic and reliable method, provided a good
water quality in terms of low content of organic compounds is given. Substances like iron and manganese, staining and clouding influence the water condition and the disinfection process. The absorption coefficient or transmittance of the water for UV is critical. To ensure an effective disinfection, the operating conditions must therefore be carefully monitored and controlled. Variations in the transmittance of the water can be compensated for by adjusting lamp power and/or flow rates accordingly. Thus, UV irradiance is monitored with at least one UV sensor at a representative position in the reactor to guarantee proper lamp operation.

Generally two different types are used:

• Longitudinal flow system
• Cross flow system

Typically, the reactor consists in both cases of following components:

• UV lamp
• quartz sleeve
• wiper for mechanical cleaning of quartz sleeves to protect against fouling
• UV sensor to control UV output
• power supply

Reuse Dialyzer System

A dialyzer is often referred to as an “artificial kidney.” Its function is to remove the excess wastes and fluid from the blood, when the patient’s kidneys can no longer perform that task.

Dialyzers are made of a thin, fibrous material. The fibers form a semipermeable membrane, which allows smaller particles and liquids to pass through. The dialyzer is encased in a sealed plastic cylinder about a foot long and approximately two to three inches in diameter with openings at the top and bottom. During treatment dialysate (dialysis solution) and your blood flow through the dialyzer (but they never touch). Fresh dialysate from the machine enters your dialyzer through one opening and blood enters through the other. Wastes are filtered out of your blood into the dialysate. Dialysate containing waste products leaves the dialyzer and is washed down the drain, while the cleaned blood goes back into your body.



A dialyzer is often referred to as an “artificial kidney.” Its function is to remove the excess wastes and fluid from the blood, when the patient’s kidneys can no longer perform that task.

Dialyzers are made of a thin, fibrous material. The fibers form a semipermeable membrane, which allows smaller particles and liquids to pass through. The dialyzer is encased in a sealed plastic cylinder about a foot long and approximately two to three inches in diameter with openings at the top and bottom. During treatment dialysate (dialysis solution) and your blood flow through the dialyzer (but they never touch). Fresh dialysate from the machine enters your dialyzer through one opening and blood enters through the other. Wastes are filtered out of your blood into the dialysate. Dialysate containing waste products leaves the dialyzer and is washed down the drain, while the cleaned blood goes back into your body.
Dialyzers can remain functional after more than one use, which is why many facilities reuse them. Dialyzers are reused for a certain number of times or until it no longer works efficiently, whichever comes first. Each doctor sets his or her own policy for the maximum number of reuses. Some dialysis facilities do not reuse dialyzers, and patients at those facilities are given new dialyzers for each hemodialysis session.

Patients are given the choice of whether or not to reuse their dialyzers. Facilities that reuse must follow strict guidelines to ensure the reused dialyzers are labeled with the patient’s name, cleaned properly, sterilized and working so the patient can have an optimal dialysis treatment.

How is reuse performed?

Patients only reuse their own dialyzer, meaning that no other patient has or will ever use it. Dialyzers are never shared between patients. After your dialysis session is complete, a facility member (either your renal nurse or a patient care technician) will take you off the dialysis machine and seal your dialyzer, which is labeled with your name, in a plastic bag. The dialyzer is then sent to a reuse technician who will follow strict procedures to make sure your dialyzer is clean, sterile and in good working condition before you use it again.

The reuse technician will first do a visual inspection of the dialyzer for blood or fiber clots. The technician will also note the number of times the dialyzer has been used. If the dialyzer is due to be replaced, the technician will replace it with a new one in the size prescribed by the physician. If the dialyzer can be reused, the technician will place it into the reuse machine to start the cleaning process.

The reuse machine cleans the dialyzer using water treated with reverse osmosis. This water is highly purified and cleans the dialyzer without leaving traces of particles and chemicals. After cleaning, the machine performs a pressure test and blood volume test. The pressure test checks for any holes in the dialyzer. The blood volume test ensures that the dialyzer’s capacity is above 80% of the dialyzer’s stated size. If there are any holes in the dialyzer, or if the blood volume is less than 80% of the dialyzer’s size, it is replaced with a new one. If any problems are detected during the reuse test, the reuse machine indicators let the reuse technician know, and the dialyzer is disposed of in the proper manner.

After the reuse machine has cleaned and tested the dialyzer, it will then be filled with disinfectant and stored for at least 11 hours. Just before the patient’s next dialysis treatment, the dialyzer is rinsed with saline solution until all disinfectant is removed. A test is performed to make sure no disinfectant is left in the dialyzer. Once it is tested, the dialyzer is ready to use for the dialysis treatment.


Is reuse safe?

Various studies have examined the issue of reuse. These studies have found that the mortality rate between patients who reuse dialyzers and patients who do not was the same.
Dialysis facilities that reuse dialyzers must follow strict guidelines set forth by the Association for the Advancement of Medical Instrumentation (AAMI). The AAMI guidelines make provisions for patient safety, among them:

• A dialyzer must be clearly labeled with the patient’s name and only used for the same patient.
• A dialyzer must be tested after each use to make sure it is working properly.
• A dialyzer must be tested after rinsing for any traces of disinfectant that may remain.
• Patients must be monitored for any reactions due to reuse.

Does reuse affect dialysis outcomes?

Different factors can affect your Kt/V and URR (urea reduction ratio), standard measures of how effective your dialysis treatments are. Although reuse may affect Kt/V and URR levels, following the correct standards of reuse for monitoring fiber volumes and testing the reuse dialyzers makes this a rare issue. If you are on reuse and are concerned about your Kt/V or URR levels, talk to your renal nurse and your kidney doctor.

What are the advantages of reuse?

Reuse can be helpful to the patient and to the planet.
Patient advantages of reuse Since each dialyzer is inspected by a reuse technician, the technician can note any blood clots in the dialyzer and alert a renal nurse. Blood clots could mean you are not getting enough heparin, which is a medicine given before and throughout hemodialysis. Heparin thins the blood to allow it to pass easily through the dialyzer and prevent it from clotting, which would reduce the dialyzer’s ability to remove wastes and fluid. Blood clots in the dialyzer may make your dialysis session less effective and can lower your Kt/V.

Environmental advantages of reuse

Dialyzer reuse helps to reduce negative environmental consequences in several ways. On average, it only takes 9.6 reuse dialyzers to treat one patient for one year, versus an average of 153 single-use dialyzers. The reuse of all dialyzers in a single year would eliminate the production of up to 46 million dialyzers and reduce the amount of medical waste ending up in landfills by more than 62 million pounds.

Dialyzer reuse also reduces the amount of harmful toxins created by waste processing. In order to be properly disposed of, dialyzers first have to go through a decontamination process requiring they either be incinerated or microwaved before being sent to landfills. When dialyzers are incinerated, the process produces emissions and ash that have negative health effects on the surrounding communities. While the microwave process does not produce harmful toxins, it does nothing to reduce the amount of medical waste that ends up in landfills.

By choosing dialyzer reuse, you can dramatically reduce the negative impact on the environment. Dialyzer reuse reduces your carbon footprint, helps relieve America of its dependence on crude oil, sends less non-biodegradable waste to landfills and ultimately benefits the dialysis patient by keeping costs lower without compromising clinical outcomes.

Interesting about this product?

Call : PT. Tirta Teknosys, with Hospital Division : (021) 9897 1156 or 0813 1526 2722
Download Brochure here:

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Extended Aeration System

The first stage in the treatment process is screening. Screening iscarried out using a static stainless steel retaining screen. Removal of solids isessential and results in higher treatment efficiencies for downstream biologicalsystem. Screening also ensures safety for transfer pumps which otherwisewould ultimately clog. The wastewater after screening enters an aeratedequalization tank.

The equalization tank is aerated by fine pore subsurface diffusers to preventsettling of solids and also to build up the dissolved oxygen level in thewastewater. Aeration ensures complete mixing of the wastewater and thesolids are maintained in suspension. Settling of solids could lead toaccumulation and stagnation, leading to anaerobic and septic conditions, theresult being strong odor problems. Aeration also aids in maintaining a residual dissolved oxygen level in the wastewater, which aids in treatmentefficiency.

Equalization pumps (one operating and one-100% standby) transferwastewater from the equalization tank to the extended aeration tank. Air-liftpumps are used for equalization pumps, up to a flow of 10,000gal/day. Theextended aeration process is a suspended growth biological treatmentprocess wherein the micro-organisms grow in the suspended form. A higherlevel of micro-biological population is maintained in the tank. The aerationtank is continuously aerated with fine pore subsurface AIRMAX diffusers. Theentire process is aerobic in nature.

Micro-organisms in their endogenous phase of respiration receive less food incomparison to the food available. This process is more popularly termed as“cannibalism”. Micro-organisms eventually consume themselves when notadequate food is available. The organic matter is consumed and biologicallydegraded to stable end products.

Extended aeration processes are very popular for sewage treatmentapplications. Waterworks has EA systems operating around the globe for thisapplication in remote camp sites, hotels, hospitals and resorts.Wastewater after extended aeration treatment flows by gravity to thesecondary clarifier. The biomass settles by gravity and the supernatantoverflows the weirs to the adjoining chlorine contact tank.

The settled biomassis air-lifted and recycled to the extended aeration tank to maintain thepopulation of biomass. The extended aeration tanks is operated at a MLSSlevel of 3000 to 3500 mg/L.

The food to micro-organism ratio is maintainedbetween 0.1 and 0.15 When the biomass concentration exceeds the required MLSS level in theextended aeration tank, sludge is wasted to the sludge holding tank.

Thesludge tank is an aerated tank where the waste biomass is held and aeratedcontinuously. In the absence of any organic matter entering the sludge tank,the biomass digests itself thereby concentrating and thickening itself.

The chlorine contact tank is a baffled tank to promote contact and mixing fordisinfection. The treated wastewater exits the chlorine contact tank.