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					                                                                                 E-VISION 2009

                       WASTE WATER TREATMENT IN NEPAL

                              * Ajay Kumar Jha, **Nawraj Bhattarai
                *Department of Municipal and Environmental Engineering
                      Harbin Institute of Technology, Harbin, China
                  **Lecturer, Department of Mechanical Engineering
                  Institute of Engineering, Tribhuvan University, Nepal


The existing treatment plants and sewerage systems face number of problems in Nepal. In most cases, treatment
systems are not functioning, or operating at far below the capacity. In addition, many towns of the country are
unable to operate schemes in a financially viable manner. The increasing trend of construction of sewers by
municipal authorities without considering treatment facilities is posing serious threats to the environment. All
industrial wastewater in most cases are directly discharged into local water bodies without proper treatment. So far
rivers and streams in the Kathmandu valley receive raw domestic sewages and untreated industrial wastes. In this
context, the present paper presents about the development trend of wastewater treatment plants in the world and
status of existing plants in Nepal.

Keywords: Waste water treatment, Financially viable, Sewage system

1. Introduction

1.1 Waste Water                                               commonly used for the separation.            Primary
Wastewater is any water that has been adversely               treatment removes 45 to 50 percent of the pollutants.
affected in quality by anthropogenic influence. It
comprises liquid waste discharged by domestic
residences, commercial properties, industry, and/or
agriculture and can encompass a wide range of                 1.2.2 Secondary Treatment
potential contaminants and concentrations. Sewage is
correctly the subset of wastewater that is                    After primary treatment, wastewater still contains
contaminated with feces or urine. "Sewage" includes           solid materials either floating on the surface,
domestic, municipal, or industrial liquid waste               dissolved in the water, or both. Under natural
products.                                                     conditions, these substances would provide food for
                                                              such organisms as fungi, algae, and bacteria that live
1.2 Waste water treatment                                     in a stream or lake. In this process, wastewater is
As the name implies, Waste water is mostly water; a           separated from the organisms and solids, disinfected
very small portion is waste material. What happens in         to kill any remaining harmful bacteria, and released
a wastewater treatment plant is essentially the same          to a nearby lake, river, or stream. Secondary
as what occurs naturally in a lake or stream. The             treatment is largely a biological process and
function of a wastewater treatment plant is to speed          microorganisms convert non settle able solids to
up the process by which water cleanses (purifies)             settle able solids. It removes the pollutants--up to 85
itself. A treatment plant uses a series of treatment          or 90 percent altogether.
stages to clean up the water so that it may be safely
released into a lake, river, or stream. Major steps are:      1.2.3 Tertiary Treatment

1.2.1 Primary Treatment                                       After primary and secondary treatment, municipal
                                                              wastewater is usually disinfected using chlorine (or
In primary treatment, sand, grit, and the larger solids       other disinfecting compounds, or occasionally ozone
in the wastewater are separated from the liquid.              or ultraviolet light). An increasing number of
Screens, grit chamber and settling tanks are most             wastewater facilities also employ tertiary treatment,
                                                              often using advanced treatment methods. Tertiary

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treatment may include processes to remove nutrients       treatment of industrial wastewaters and biological
such as nitrogen and phosphorus, and carbon               sludge. Some wastewater may be highly treated and
adsorption to remove chemicals.                           reused as reclaimed water. For some waste waters
                                                          ecological approaches using reed bed systems such as
1.2.3 The Stuff that’s Left Behind                        constructed wetlands may be appropriate. Modern
                                                          systems include tertiary treatment by micro filtration
Sludge requires proper treatment and disposal, and        or synthetic membranes. After membrane filtration,
can often be reused. Sludge handling methods are          the treated wastewater is indistinguishable from
designed to destroy harmful organisms and remove          waters of natural origin of drinking quality. Nitrates
water. The end product of the sludge handling             can be removed from wastewater by microbial
process is a relatively dry material known as “cake.”     denitrification, for which a small amount of methanol
It can be applied to agricultural land as a soil          is typically added to provide the bacteria with a
conditioner, placed in landfills, or cleanly burned. At   source of carbon. Ozone Waste Water Treatment is
some plants, sludge serves as a fuel to produce           also growing in popularity, and requires the use of an
energy.                                                   ozone generator, which decontaminates the water as
                                                          Ozone bubbles percolate through the tank. Disposal
1.3 Waste Water Treatment Processes                       of wastewaters from an industrial plant is a difficult
There are numerous processes (like Activated sludge       and costly problem. Most petroleum refineries,
systems, Advanced Oxidation Process, Aerated              chemical and petrochemical plants have onsite
lagoon, Aerobic granular reactor, Aerobic treatment       facilities to treat their wastewaters so that the
system, Anaerobic clarigester, Anaerobic digestion,       pollutant concentrations in the treated wastewater
API oil-water separator, Anaerobic lagoon, Bead           comply with the local and/or national regulations
Filter, Belt press, Bioconversion of biomass to mixed     regarding disposal of wastewaters into community
alcohol fuels, Bioreactor, Bioretention, Biorotor,        treatment plants or into rivers, lakes or oceans.
Bioroll, Biolytix, Carbon filtering, Cesspit, Chlorine
disinfection, Combined sewer, Composting toilet,
Constructed wetland, Dissolved air flotation,
Distillation, Electrocoagulation, Electrodeionization,    2. Historical Aspects and Development Trend of
Electrolysis, Electro-Fenton process, Expanded            Wastewater Treatment
granular sludge bed digestion, Facultative lagoon,
Fenton's reagent, Flocculation & sedimentation,           In the Mesopotamian Empire (3500 to 2500 BC)
Fluidized Bed Biofilter, Flotation process, Froth         some homes were connected to a storm water drain
flotation, Fuzzy Filter, Humanure (composting),           system to carry away wastes. In Babylon there were
Imhoff tank , Iodine, Ion exchange, Living machines,      latrines which were connected to 18 inch diameter
Membrane bioreactor, Nanotechnology, N-Viro,              vertical shafts lined with perforated clay pipes
Ozone and Ultrasound, Parallel plate oil-water            leading to cesspools. In the Indus city of Mohenjo-
separator, Recirculating Sand Filter, Reed bed,           Daro (Pakistan) the wealthy as well as some of the
Retention basin, Reverse osmosis, Rotating                peasants used latrines and cesspools. These were
biological contactor, Sand filter, Septic tank,           connected to drainage systems in the streets from
Sequencing batch reactor, Sewage treatment,               whence the liquid flowed to cesspools or through
Stabilization pond, Submerged aerated filter,             drains to the nearest river. Archaeologists have found
Treatment pond, Trickling filter, Ultrafiltration         four separate drainage systems at King Minos’ Royal
(industrial), Ultraviolet disinfection, Upflow            Palace at Knossos (Crete), which dates from 1700
anaerobic sludge blanket digestion, Wet oxidation         BC. The wastewater drained through terracotta pipes
etc) that can be used to clean up waste waters            which were joined with cement into stone sewers to
depending on the type and extent of contamination.        the Kairatos River. From 2000 BC the island of Crete
Most wastewater is treated in industrial-scale            had a drainage system made up of terracotta pipes.
wastewater treatment plants (WWTPs) which may             Wolfe (1999) states that many of the drains are still
include physical, chemical and biological treatment       in use today. There was a recent discovery of a stone
processes. The most important aerobic treatment           lavatory with running water in a royal tomb from the
system is the activated sludge process, based on the      Western Han dynasty (206 BC to AD 24) in the
maintenance and recirculation of a complex biomass        central province of Henan, China (Rennie 2000). The
composed by micro-organisms able to absorb and            Ancient Greeks (300 BC to 500 AD) tackled the
adsorb the organic matter carried in the wastewater.      problem of waste in a different way. They had public
Anaerobic processes are widely applied in the             latrines which drained into sewers which conveyed

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the sewage and storm water to a collection basin               water level in the horizontal flow bed and low water
outside the city to agricultural fields for irrigation.        level in the vertical flow bed showed the best
                                                               elimination performance. The aril removal rate
3. Waste Water Treatment in Nepal                              constants (k-values) turned out to be very high
                                                               (especially of the vertical flow bed) compared with
In Nepal, surface water pollution is one of the serious        literature values of other subsurface flow constructed
environmental problems in urban centers due to the             wetlands. For the vertical flow bed kCOD was 0.22
discharge of untreated wastewater into the river-              m/d and kNH sub (4)-N was 0.85 m/d during serial
system, turning them into open sewers. Pollution of            operation. For kNH sub (4)-N a strong correlation
rivers is more severe and critical near urban stretches        with the hydraulic loading rate and the COD inlet
due to huge amounts of pollution load discharged by            concentration was found (Laber, 1998). Beside these
urban activities. For example, Bagmati river in
Kathmandu Valley. The river suffers from severe                          Capacity
                                                               Plant                    Status          Remarks
pollution these days. The observed dry season                             MLD
average of biochemical oxygen demand (BOD) in the          Dhobighat     15.4       Not            Needs
river is in the range of 20–30 mg/liter and total coli                              Operational    Rehabilitation
form are as high as 104–105 MPN/100 ml. Per capita         Kodku         1.1        Partial        Needs
                                                                                    Operational    Rehabilitation
pollution load discharge of urban areas has been
                                                           Sallaghari    2.0        Partial        Needs
estimated to be about 31gBOD/capita/day in Bagmati                                  Operational    Rehabilitation
River. Regression analysis reveals pollution loads         Hanumangha    0.5        Under          Needs
steadily increasing nearly in step with the trend in       t                        Construction   Rehabilitation
urbanization. The dissolved oxygen (DO) level of the       Guheshwori    17.3       In operation
Bagmati is declining at an average annual rate of          KMC
nearly 0.3 mg/liter/year (Karna, 2001). Unplanned          Facilities
urbanization and industrialization occurring in the        Teku                     Operating      Treats Septage
cities of Nepal may be largely responsible for this        Propakar                 Operating      Just placed in
grave situation. Inadequate sewerage, on-site                                                      operation
sanitation, and wastewater treatment facilities in one         systems, few constructed wetlands have already been
hand, and lack of effective pollution control measures         designed and some are under construction for the
and their strict enforcement on the other are the major        treatment of leach ate and seepage. The majority of
causes of rampant discharge of pollutants in the               urban areas do not have access to sewerage networks
aquatic systems.                                               except three cities of Kathmandu Valley. The
                                                               domestic wastewater generated from these cities is
Wastewater treatment plants are almost non-existent            discharged into the local rivers without any
in the country except for a few small sized in the             treatment. Out of the total urban population only 76
Kathmandu Valley and other cities and even these are           % have access to toilets while the remaining use
not functioning well. Successful implementation of a           opens spaces, riverbanks for defecation. The present
few constructed wetland systems within the past                sewerage network in Kathmandu and Lalitpur
recent years has attracted attention to this promising         consists of about 200 km of sewer lines. Most of
technology. A two-staged subsurface flow                       sewage except Patan area is supposed to flow by
constructed wetland for hospital wastewater                    gravity to the sump well at Sundarighat, from where
treatment and constructed wetlands for treatment of            it is to be pumped to the wastewater treatment plant
grey water and seepage is now becoming a                       at Dhobighat. This pump is provided with 2
demonstration site of constructed wetland systems in           anaerobic ponds and 1 facultative pond; having
Nepal. To treat the wastewater of a hospital at                design capacity 15.4 MLD. The plant is not in
Dhulikhel ( 40 km far from Kathmandu), a two-stage             operation due to non-functioning of pumping station
constructed wetland was built with a settlement tank,          and breakage of pumping main laid across the bed of
a horizontal flow bed as first stage and a vertical flow       Bagmati River. Wastewater facilities development
bed as second stage. The plant is operated without             and management is poor. The treatment plant at
electric power. The aim was the elimination of                 Balkumari 1.1 MLD capacity is partial in operation.
organic compounds, nitrification and a significant             It receives sewage by gravity from eastern part of
reduction of indicator bacteria. Different phases of           Patan. The plant is provided with two anaerobic
operation (high and low water level within the soil            ponds, one facultative and one maturation pond. The
profile, serial operation, one stage operation) were           sewage treatment at Bhaktapur, 2 MLD capacities is
investigated, of which the serial operation with high          not in operation due to failure in pumping station and

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farmers tapped the wastewater to irrigate their           waste, sewer and sewage treatment systems are
cropland. The Department of Water Supply and              lacking not functioning, or operating at far below the
Sewerage (DWSS) has started to construct a sewage         capacity. In addition, many towns of the country are
system of about 6 km. of sewer line and a treatment       unable to operate schemes in a financially viable
plant (lagoon type) on 20.54 hectors to serve design      manner. The increasing trend of construction of
population of 53000 in Thimi, Bhaktapur. The newly        sewers by municipal authorities without considering
constructed WWTP 17.3 MLD at Guheshwori by                treatment facilities is posing serious threats to the
BASP is the only plant operational in the Valley.         environment. All industrial wastewater in most cases
                                                          are directly discharged into local water bodies
                                                          without any treatment. So far rivers and streams in
4. Conclusion                                             the Kathmandu valley receive raw domestic sewage
                                                          and untreated industrial waste.
Treatment of wastewater is a relatively modern
practice. While sewers to remove foul-smelling
water were common in ancient Rome, it was not until
the 19th century that large cities began to understand
that they had to reduce the amount of pollutants in
the used water they were discharging to the
environment. Despite large supplies of fresh water
and the natural ability of water to cleanse itself over   References
time, populations had become so concentrated by
1850 that outbreaks of life-threatening diseases were         1.
traced to bacteria in the polluted water. Since that          2.
time, the practice of wastewater collection and                    ry.htm
treatment has been developed and perfected, using             3.
some of the most technically sound biological,                     blishing.nsf/AttachmentsByTitle/Wastewate
physical, chemical, and mechanical techniques                      r+Treatment+History/$FILE/The+History+o
available. As a result, public health and water quality            f+Wastewater+Treatment3.pdf
are protected better today than ever before. The              4.
modern sewer system is an engineering marvel.                      History/HistSewTreat.pdf
Homes, businesses, industries, and institutions               5.
throughout the modern world are connected to a                     199-6601581_ITM
network of below-ground pipes which transport                 6.
wastewater to treatment plants before it is released to            =14052210
the environment.                                              7.
        Table: Waste water treatment Plants in Nepal          8.
In Nepal, there are no many waste water treatment
plants. The existing treatment plants and sewerage
systems face a number of problems. In most cases,


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