Domestic sewage is one of the major wastes disposed every day. It is
99.9% pure water by weight, rest of the 0.1% contains variety of dissolved and
suspended impurities which causes significant problems and also contains
disease causing microbes 1. Most of the communicable diseases are due to
unsafe water, most of which is contaminated either by sewage or agricultural
run-off. At Govardhan Eco Village (GEV), the domestic sewage waste is treated by
Soil Biotechnology Method.
SBT consists of impermeable containment and incorporates soil,
formulated granular filter media and a select culture of organisms such as
earthworms and plants. It involves a combination of physical and biological
process for processing of waste water and it derives its fundamental principle
from the functioning of a terrestrial ecosystem. It is a natural
bio-geochemical cycle of nature and hence proves to be most effective
eco-friendly technology for waste water treatment. The SBT plant at Govardhan
Eco Village recycles 30,000 liters of sewage every day 2.
Chemical and Microbial analysis of domestic sewage water is done
before and after treatment to prove the benefits of this eco-friendly
Following water quality parameters were analyzed to assess the water
pollution status: (1) pH (2) Total dissolved solid (TDS) (3) Total Suspended
Solids (TSS) (4) Dissolved oxygen (DO) (5) Chemical oxygen demand (COD) (6)
Biochemical oxygen demand (BOD) (7) Total Kjeldhal Nitrogen (8) Oil and Grease
(9) Detection of sodium, potassium, Nickel, Copper and Aluminum by AAS (10) Enumeration
of total viable bacteria, coliforms, psychrophiles and thermophiles (11)
Detection of fungi and actinomycetes.
Water quality parameters and their effects on agriculture
The water was collected from GEV, Palghar district in order to study
physico-chemical and microbial characteristic of domestic sewage water pre- and
post treatment. The samples were collected following the standard methods
described for sampling. The standard methods and procedures were used for qualitative
and quantitative estimation of water quality parameters.
3.1 pH: pH is the measure of the acidity or alkalinity of a solution. Water
pH between 6.5 and 8.5 is considered to be the advantageous for irrigation. pH
values above and below the normal range, indicates that action needs to be
taken to get better crop performance3.
3.2 COD: Chemical
oxygen demand is a measure of the amount of oxygen necessary for the chemical
oxidation of organic matter. It can be high without any negative effects for
the plants and the soil. In some cases high organic matter content is
considered positive as it improves the water holding capacity of the soil on
the long term.
3.3 BOD: Biological oxygen demand is a measure of the amount of oxygen
required for the biological oxidation of organic matter. It can be used as a
measure to find out the efficiency of waste water treatment plants.
3.4 TSS: Total suspended solids are
the dry-weight of particles blocked by a filter 4. TSS, measured in mg/l, can be
3.5 TDS: “Total dissolved solids”
refer to any minerals, salts, metals, cations or anions dissolved in water. It comprises of inorganic salts and
some minute amounts of organic matter that are dissolved in water 5, 6.
3.6 Total kjeldhal
nitrogen: The nitrogen cycle is the means by which
atmospheric nitrogen is made available in different forms to living organisms.
From the basic molecules of ammonia, nitrate and nitrite to the more complex
amino acids and proteins, nitrogen is essential for living organisms to
function. It is an important part in the smooth operation of many wastewater
treatment plants 7, 8.
3.7 OIL AND GREASE: Oil and grease is organic toxic waste which causes ecology damages
for aquatic organisms, plant, animal, and is mutagenic and carcinogenic for
human being. They form a layer on water surface that decreases dissolved oxygen
3.8 Aluminum: Can cause non-productivity in acid soils (pH < 5.5), but more
alkaline soils at pH > 7.0 will precipitate the ion and eliminate any
3.9 Nickel: Toxic to most of the plants ranging 0.5 mg/l – 1.0 mg/l. Toxicity
can be reduced at neutral or alkaline pH 10.
3.10 Copper: Toxic to most of the plants ranging 0.1 to 1.0 mg/l in nutrient
solutions. Copper can cause leaf chlorosis as well as the suppression of root
3.11 Sodium: Sodium exists in almost all irrigation water and is not essentially
a cause for concern unless high concentrations are present. High concentrations
(> 70 mg/L) can be dangerous to both plants and soils. Sodium in irrigation
water can be absorbed by roots and flora, and foliar burning can occur if excess
amounts accumulate in leaf tissue 12.
3.12 Potassium: The potassium (K+) cation behaves similarly to sodium in
the soil and is commonly found in natural waters in small amounts.
3.13 Microbiological analysis:
Since the composition of wastewater varies, the
types and numbers of organisms will fluctuate. Fungi, protozoa, algae, bacteria
and viruses are present. Raw sewage may contain millions of bacteria per
milliliter including the coliforms, streptococci, anaerobic spore-forming
bacilli, the proteus group and other types originating in the intestinal tract
of humans. The causative agents of poliomyelitis, hepatitis, typhoid, dysentery
and cholera may occur in sewage. Certain bacteriophages are readily isolated
The potential methane producers such as Methanococcus, Methanobacterium, Methano-sarcina contribute to the
production of anaerobic and temperature elevated conditions in sewage13.
Bacterial growth is sensitive to temperature because high temperature can
increase the fluidity of the phospholipid bilayer which leads to cell lysis.
However, bacteria are known to have higher enzymatic activity at higher
temperature because of increased thermal energy. For example, when thermophilic
sludge treatment is compared to mesophilic treatment, the sludge biodegradability
is higher with thermophilic degradation 14.
3.13.1 Total viable count
In routine analysis the total number of bacteria present in 1 ml of
sewage is determined by standard plate count method. One set of plates is
incubated at 370 C for 48 h (mesophilic bacteria). Another set of
plates is incubated at 220 C for 72 h (psychrophilic bacteria) and
yet another set of plate is incubated at 550C for 72 h (thermophilic
bacteria). After incubation the colonies are counted and the amount of cfu/ml
(colony forming units) can be calculated 15.
Plate count technique is useful in determining the efficiency of
operation for removing or destroying organisms. A microbial count can be made
before and after a specific treatment and results obtained indicate the degree
to which the bacterial population has been reduced. A water sample containing
less than 100 bacteria per ml is considered to be safe 5.
The total number of
Non pathogenic bacteria grow mainly at lower temperatures. It is
important that Gram-negative bacteria in water produce lipopolysaccharides in
their cell wall which can be toxic – like endotoxins of pathogenic bacteria.
Because of this, their numbers in water should be constantly monitored. A large
increase in their numbers is evidence of the presence of easily available
organic compounds in the water. Theoretically, the presence of 0.1 mg organic
carbon in water can result in an increase of bacteria up to 108 cfu
in 1 ml.
Phosphorus is also a factor which stimulates the growth of
psychrophilic microorganisms. Adding even small amounts of this element (i.e.,50mg/l)
causes 10 times the acceleration of bacterial growth in a water treatment plant
The total number of
More dangerous are high numbers of bacteria growing at 370C,
because among this high population, pathogenic forms may be found which are
dangerous for human health. High number of bacteria in samples of water can
prove that water treatment processes proceed badly or that polluted water is
The total number of thermophilic
It is an index of production of gases such as methane that elevate
the temperature of sewage and allow the proliferation of thermophilic bacteria14.
3.13.2 Total coliform and
fecal coliform (MPN – Most probable number)
It is statistical method based on the probability theory. In this
technique, the sample is serially diluted till the numbers of organisms reach
the point of extension. From each of these dilutions several multiple tubes of
a specific medium are inoculated. Presence of organism is indicated by acid and
gas in the medium. Pattern of positive and negative test results are then used
to estimate the number of coliforms in the original sample. Since the test
gives the most probable number of organisms present in the sample. it is also
known as MPN test16.
3.13.3 Study of biological
Azotobacter is a free living, non symbiotic nitrogen fixing
bacterium that brings about biological nitrogen fixation 17. Since the sewage
is SBT treated it is possible that these valuable microorganisms may enter the
treated sewage by diffusion from the soil. Enrichment technique is used to
increase the number of this organism as its number is very few in soil samples
and hence in the treated sewage.
Materials and methods:
4.1 pH: pH was determined by pH metry using a pH meter18.
4.2 COD: 50.1N Pottasium dichromate, 0.1M sodium thiosulphate, 2M sulphuric
acid, 1% starch solution. COD was determined by titrimetry by using procedure
4.3 BOD: 50.5% Allyl thiourea, 1N sulphuric
acid, sodium hydroxide. BOD was determined by titrimetry by using procedure
4.4 TSS: APHA 2540 D Total
Suspended Solids Dried at 103–105°C 19.
4.5 Oil and grease: American Public Health Association (APHA)
5520 B. Partition-Gravimetric Method 20.
Raw and treated sewage effluent samples were incubated overnight at
370C, before analysis.
The samples were sampled to enumerate total viable counts and total
coliform counts. Also, the fungi and actinomycetes present in the samples were
studied. The sample was also checked for the presence of nitrogen fixing
bacteria, Azotobacter spp.
The samples were 10-fold serially diluted and the total viable count
was carried out using appropriate dilutions, sterile molten nutrient agar
medium and incubation conditions by pour plate method15. Determination of
total coliform count was carried out by MPN (three tube method) using single
and double strength Lauryl tryptose broth16.
For the study of fungi and actinomycetes, a loopful of each of the
samples were streak isolated on sterile Sabouraud’s dextrose agar and sterile
Kenkunight and munnair’s agar plates respectively5. Azotobacter spp was isolated by enrichment in Sterile Ashby’s
mannitol broth medium and subsequent streaking on sterile Ashby’s mannitol agar