N-Tox®
is a patented nitrification toxicity monitoring system that
provides early warning of activated sludge failure and consequent
wastewater treatment works breakdown, and helps prevent ammonia
pollution of the aqueous environment.
The
product detects nitrous oxide (N2O), a harmful
greenhouse gas with global warming potential almost 300 times that
of carbon dioxide.
The unique
features of N-Tox® include:
-
critical
early-warning device, used to monitor nitrification
effectiveness in municipal and industrial activated sludge
systems;
-
real time response
allowing proactive management by providing an earlier warning
compared to other systems because the indicator of the failure
of the treatment process, N2O, is produced
instantaneously;
-
robust,
non-invasive technique based on gas-phase detection which
avoids sampling of activated sludge and eliminates associated
probe fouling and maintenance issues;
-
simple, low cost
technology requires minimal operator intervention and utilises
a proven, standard N2O detector;
-
innovative design
comprises an integral sample pump, gas conditioning device,
non-dispersive IR gas analyser, auto-calibration system and
data logging unit, housed within an IP65 enclosure;
-
no expensive
consumables such as chemical reagents or calibration standards.
How it Works
Prior research at
Cranfield University has demonstrated that nitrogen oxide (N2O)
is rapidly detected when nitrification starts to fail. The rate of
N2O production is linked to oxygen depletion, presence
of toxic substances and ammonia shock loadings. Increases in
levels are directly related to nitrification failure. Hence,
measurement of the N2O off-gas level allows the
monitoring of nitrification performance to prevent breakthrough of
ammonia in final effluent.
Using N-Tox®
to detect an increase of N2O above the start of an
activated sludge aeration lane or a trickling filter means that at
least one hydraulic retention time of the final clarifier would
pass before nitrification failure. The graph below demonstrates
that the time lag between detection of increased N2O
and the appearance of ammonia provides typically seven hours
warning of nitrification failure.
Once a failure is detected, plant operators and asset managers can
implement a number of process options to restore nitrification
including increasing aeration rates, bypassing influent to storage
tanks, recycling final effluent to works inlet, or controlling
return of high ammonia sludge liquors.
Applications
N-Tox® can be
used to monitor any activated sludge system in either municipal
sewage or industrial effluent treatment systems. Many treatment
works that discharge direct to the aqueous environment are
consented for ammonia at < 5 mg/l as NH3-N. These
plants rely on ammonia removal through bacterial conversion to
nitrate.
Inhibition by aeration failure, toxic chemicals or high ammonia
concentrations can result in a wastewater treatment works not
meeting its required ammonia consent. Some industrial effluents,
such as landfill leachate or pharmaceutical wastewaters, have high
ammonia levels. The requirement for an N-Tox® alarm
here is critical as the consequences of nitrification failure are
more serious.
N-Tox® can also be used to quantify N2O
greenhouse gas emissions from wastewater treatment plants. This is
an area of increasing concern to plant operators and regulators
alike, due to the particular potency of N2O as a
geeenhouse gas.
N-Tox®
Equipment Specification
: Measurement
|
Gas Type :
|
 |
N2O (nitrous
oxide, dinitrogen oxide)
|
|
Measuring Method :
|
Non dispersive IR
absorption with CO2 luft cell
|
|
Measuring Limit :
|
2000 ppm N2O
(4000 mg/m3)
|
|
Resolution :
|
1 ppm N2O (2 mg/m3)
|
|
Accuracy :
|
+/- 2 ppm N2O
(± 4 mg/m3)
|
|
Lower Detection Limit :
|
2 ppm N2O
(4 mg/m3)
|
|
Cross Sensitivity :
|
1 ppm N2O
per 1000 ppm CO2
|
|
Response Time :
|
8 - 30 seconds (dependent
gas-sample line length)
|
|
Monitoring Interval :
|
1 second
|
|
Operating Temperature :
|
0 - 50°C
|
|
Relative Humidity :
|
0-100% RH,
non-condensing (at operating temperature)
|
Features
|
Sampling :
|
|
Continuous
single-point monitoring (multi-point available on request)
|
|
Sample Gas Conditioning :
|
Gas filter +
semi-permeable membrane dryer
|
|
Offset & Drift Compensation :
|
Auto drift
compensation
|
|
Calibration :
|
Factory set with
auto adjustment for temperature drift, IR source aging and
pressure changes
|
Electrical &
Compliance Data
|
Power Supply :
|
|
110 - 240 VAC,
50/60 Hz
|
|
Power Consumption :
|
0.015 kW
|
|
Max Current :
|
1 A
|
|
Certification :
|
Components to
UL61010A-1, CSA 22.2, CE Mark
|
Enclosure Details
|
Ingress Protection:
|
|
IP65
|
|
Material :
|
Glass Fibre
|
|
Dimensions :
|
height 647mm,
width 430mm, depth 250mm
|
Connections
|
Inlet :
|
|
Hose Barb for 4mm
ID plastic pipe (max length 15m)
|
|
Purge :
|
Hose Barb for 4mm
ID plastic pipe (max length 15m)
|
|
Exhaust :
|
Hose Barb for 4mm
ID plastic pipe (max length 15m)
|
Data Display, Inputs
& Outputs
|
Display lights :
|
|
LCD display +
Monitor On, System Fault and Alarm indicator
|
|
Keypad :
|
Menu navigation +
Enter and Silence/Quit buttons
|
|
Data Presentation :
|
3 main operating
screens plus function screens for data display and
parameter set up
|
|
Data Storage :
|
Integral
Datalogger – 43,000 readings, battery powered
(1 year life), user settable start time and interval
|
|
Analogue Output :
|
4 - 20 mA current
loop (utilised by Datalogger)
|
|
Alarm Signals :
|
3 SPDT relays for
user assigned mg/l N2O alarm levels
|
|
Fault Signal :
|
1 SPDT relay for
system fault
|
|
Computer Interface:
|
USB + datalogging
software for launch and read out
|
|
AST Analytica
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