What is DEWATS?
Decentralized Wastewater Treatment System (DEWATS) can be described as a low maintenance treatment system, treating small volumes of wastewater for reuse or discharge within National Standards. DEWATS generally treats domestic wastewater originating from individual or groups of dwellings, businesses or institutions that are located in close proximity to each other and the DEWATS site. Unlike conventional wastewater treatment plants, DEWATS promotes technologies that use natural processes and are simples in operation and maintenance. In DEWATS, natural treatment processes are achieved through methods that make use of physical principles combined with biological activities of microorganisms. Bacteria colonies in the treatment devices are generated from microbial populations that occur naturally in the wastewater.
The size of a DEWATS can range from individual onsite systems that serve one household or institution; to shared facilities that serve up to ten households or public/community facilities serving up to 2000 households. Since the distance between the point of origin and treatment of wastewater is small, elaborate collection systems and pumping equipment is avoided thereby reducing costs. This also allows for easier reuse of treated water which again makes the whole system cost efficient.
Typical DEWATS combine the following technical treatment steps in a modular manner.
(1) Primary Treatment
- The primary treatment phase retains all settable solids and allow only dissolved solids to discharge.
- In settler, sedimentation tank, septic tank or biogas settler.
- Another type of primary treatment is sedimentation tank for collection and use of biogas generated from decomposition of settled organic particles.
(2) Secondary Treatment
- Suspended and dissolved solids in the wastewater undergo anaerobic degradation due to contact with an active sludge blanket on the bottom of each chamber.
(3) Tertiary Treatment
- It is the secondary and/or tertiary treatment phase and cleans the wastewater by biological conversion, physical filtration and chemical adsorption.
(4) Sludge Treatment
- Sludge generated from primary and secondary treatment units can be dried applying on sand beds, which is also called sludge drying beds. De-sludging intervals can be set to coincide with the dry season in order speed up the drying process.
EXISTING DEWATS IN NEPAL
| S.N. | Location Type | Year Built |
|---|---|---|
| 1 | Dhulikhel Hospital Hospital | 1997 |
| 2 | Dallu, Private House Domestic | 1998 |
| 3 | Kathmandu University Institutional | 2001 |
| 4 | ENPHO Laboratory Institutional | 2002 |
| 5 | Malpi International School Institutional | 2002 |
| 6 | Sushma Koirala Memorial Plastic &Reconstructive Surgery Hospital Hospital | 2002 |
| 7 | Kapan Monastry Institutional | 2002 |
| 8 | Private House at Dallu Domestic | 2002 |
| 9 | Septage Treatment, Pokhara Community | 2003 |
| 10 | Shuvatara School, Lamatar Institutional | 2004 |
| 11 | Surya Tobacco Industrial | 2005 |
| 12 | Private House, Bishal Nagar Domestic | 2005 |
| 13 | Sunga, Thimi Municipal | 2006 |
| 14 | Kirtipur Housing Community Community | 2006 |
| 15 | Kusunti Housing Community | 2007 |
| 16 | Ilam Polyclinic Hospital | 2007 |
| 17 | Sano Khokana Community Community | 2008 |
| 18 | Srikhandapur Community | 2008 |
| 19 | Monastry in Pharping, Dakshinkali Institutional | 2009 |
| 20 | Private House at Kirtipur Domestic | 2010 |
| 21 | Namo Bhudha Resort | 2012 |
| 22 | Thakuri Gaun Sub System | 2009 |
| 23 | Pipal Bot Sub System | 2009 |
| 24 | Srikhandapur Community Wastewater Treatment Plant | 2008 |
| 25 | Nala Community Wastewater Treatment Plant | 2012 |
| 26 | Panauti Wastewater Treatment Plant | 2009 |
| 27 | Chandeshwori Wastewater Treatment Plant | 2009 |
| 28 | Budole Wastewater Treatment Plant | 2009 |
| 29 | Landfill Site Wastewater Treatment Plant | 2009 |
| 30 | Gokarna Wastewater Treatment Plant(I) | 2012 |
| 31 | Gokarna Wastewater Treatment Plant(II) | 2014 |
| 32 | Gokarna Wastewater Treatment Plant (III) | 2016 |
| 33 | Kapan Monastry | 2002 |
| 34 | Satya Sai Sikshya Sadan | 2014 |
| 35 | School at Dallu | 2010 |
| 36 | Central Horticulture Center | 2011 |
| 37 | Neydo Monastry | 2009 |
| 38 | Kusunti Housing | 2007 |
| 39 | ICIMOD | 2010 |
| 40 | Ama Ghar | 2010 |
| 41 | Suvatara School | 2004 |
| 42 | Park Village Water Front Resort | 2011 |
| 43 | Hetauda Wastewater Treatment Kara Sub System | 2009 |
| 44 | Hetauda Waste Treatment Rapti II Sub System | 2009 |
| 45 | Hetauda Wastewater Treatment Rapti II Sub System | 2009 |
| 46 | Hetauda Industrial Wastewater Treatment Plant | 2003 |
| 47 | Bharatpur Wastewater Treatment Plant (C1) | 2009 |
| 48 | Bharatpur Wastewater Treatment Plant (C2) | 2009 |
| 49 | Surya Nepal Pvt. Limited (Staff Housing) | 2005 |
| 50 | Lumbini Medical College and Teaching Hospital | |
| 51 | Sidhartha Childern and Women Hospital (AMDA) | |
| 52 | Middle Marshyangdi Hydro Electric Power Station (Staff Quarter) | |
| 53 | Teku Septage Treatment Plant | 1998 |
| 54 | Dallu Private House (II) | 2002 |
| 55 | Septage Treatment, Pokhara | 2003 |
| 56 | Bishal Nagar | 2005 |
| 57 | Lubhoo FSTP | 2016 |
| 58 | Kupondole | 2011 |
| 59 | Hope Center Nepal | 2016 |
| 60 | Disable Children Home | 2016 |
| 61 | Basundhara I | 2013 |
| 62 | Basundhara II | 2014 |
| 63 | Imadole | 2009 |
| 64 | Chahuni | 2011 |
| 65 | kimdole | 2016 |
| 66 | ECCA | |
| 67 | Kupondole | 2010 |
| 68 | Bottlers Nepal Limited, Balaju | 2001 |
| 69 | Bottlers Nepal (Terai) Limited, Bharatpur | 2005 |
| 70 | Western Regional Hospital | 2013 |
| 71 | Chandra Ban Eco Resort | 2012 |
| 72 | Lumanti Support Group for Shelter | 2016 |
| 73 | Birat Eye Hospital | |
| 74 | Illam Polyclinic |