62.
HARVEST NITROGEN IN SEWAGE – DON’T WASTE
MONEY TO KILL IT !
This Commentary is a
rejoinder to a recent Notification from the Karnataka State Pollution Control
Board revising standards for quality of treated sewage. More specifically the KSPCB has introduced NH4-N
( Ammonia Nitrogen) and Total Nitrogen and set limits of 5 mg/L and 10 mg/L
respectively for these parameters in treated domestic sewage. The new standards are made applicable to all
STP’s including those in Residential Apartment Complexes, Commercial Complexes
and the Large STP’s of Urban Local Bodies ( ULB) such as City Municipal
Corporation, Town Municipal Corporation etc. in Karnataka.
The
KSPCB takes refuge under the plea that
the Notification has been issued following a Direction from the Central
Pollution Control Board – Delhi ( CPCB ) dt. 21-08-2015 to enforce these new
Rules.
Let
me explain why I feel both agencies, and the KSPCB in particular have missed
the Wood for the trees and why this is a Knee Jerk reaction similar to several
others which we have now come to expect from such “Expert” bodies constituted
by the Government. Md. Bin Tughlaq would
have been immensely pleased to have such worthies in his Durbar.
1.
From a reading of the brief narration given of the CPCB Direction, it is clear
that the Rules must be made applicable to Large STP’s of ULB’s and not to
distributed , decentralized small, mini and micro STP’s in Residential
apartment Complexes.
2.
Has the KSPCB got any expert technical opinion or has it conducted any public
consultation before applying the Rules across the board to all STP’s ?
3.
Has the KSPCB done even a cursory study on the technical and practical
feasibility of enforcing these Rules in the Micro and Mini STP’s ?
4.
Has the KSPCB explored other alternative technologies, methods and means of
reducing Nitrogen pollution in the lakes and water bodies ? Is Nitrogen control in the STP at great cost,
expenditure of energy and chemicals the only solution ?
The
Answers to all these questions can only be a resounding NO.
Here is an
alternative method to beneficially
harvest Nitrogen in sewage and make money instead of pouring money down the STP
drain.
About
25 years ago, I was summoned by Sri. Srihari Khoday, the liquor Baron of the
day in Karnataka to study treatment plants in their breweries and
distilleries. When the main discussions
concluded, as an aside, Mr. Khoday asked me for my opinion on the technical
feasibility of harvesting Water Hyacinth ( Eichhornia Crassipes) on a
commercial scale from lakes in Bangalore, more particularly Bellandur ( Yes –
Bellandur was polluted even in those days).
Water Hyacinth takes up huge quantities of Nitrogen and phosphorus for
growth and becomes biomass which then can be anaerobically digested to generate
Methane and energy therefrom and supply power to nearby industries. The largest
consumer in the vicinity was Hindustan Aeronautics Limited ( HAL). Twenty five years ago, this struck me as a
revolutionary idea, and out of the box thinking of a visionary businessman with
great commercial acumen.
Maybe
the Babus in those days were equally
insular to practical ideas and solutions as they are even to this day : Srihari
Khoday’s idea could not find wings to take off. I have myself proposed very economical,
practical and executable solutions to resuscitating defunct STP’s in Bangalore
to all the authorities in the Government directly concerned. Needless to say, they have fallen only on deaf
ears.
Dr.
Ananth S Kodavasal April 13, 2016
Abstract
Water
hyacinth, Eichhornia crassipes, growth and nutrient uptake rates, as influenced
by different N sources and N transformations, were measured using microcosm
aquaculture systems. Net productivity was highest in the system receiving equal
amounts of $NH_{4}{}^{+}$ and NO3 - (at 10 mg N l-1 each) and decreased in the
order of NO3 -, $NH_{4}{}^{+}$, urea (added at 20 mg N l-1 each), and methane
digestor effluent (at 6 mg N l-1). During the first 7-wk study (average ambient
air temperature was 26-28°C), biomass yields were in the range of 19-53 g dry
wt $m^{-2}\ day^{-1}$, while between the 8th and 12th wk (average ambient air
temperature was 16-22°C), biomass yields were in the range of 10-33 g dry wt
$m^{-2}\ day^{-1}$. In the systems with either $NH_{4}{}^{+}$ or NO3 -, or both
added in equal proportions, about 14-20% of the total yield was contributed by
roots, whereas in the system with urea and digestor effluent, roots contributed
about 23 and 44% of the total yield, respectively. Nitrogen and P uptake per
unit area followed trends similar to biomass yields. Nitrogen uptake rates were
in the range of 533-2,161 mg N $m^{-2}\ day^{-1}$ for the systems receiving
$NH_{4}{}^{+}$, NO3 -, and urea, while uptake rates were in the range of
124-602 mg N $m^{-2}\ day^{-1}$ for the system receiving methane digestor
effluent. Phosphorus uptake rates were found to be in the range of 59-542 mg P
$m^{-2}\ day^{-1}$. Under the most favorable conditions, maximum recorded
biomass yield was 53 g dry wt $m^{-2}\ day^{-1}$, with N and P removal rate of
2,161 mg N $m^{-2}\ day^{-1}$ and 542 mg P $m^{-2}\ day^{-1}$, indicating the
potential of water hyacinth to produce large amounts of biomass which can be
potentially used as a feedstock to produce methane.
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