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Last updated: 29/4/2013
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ELCAD wastewater metal monitor

Development of a cost-effective, low-maintenance, on-line instrument to detect heavy metal concentrations in wastewaters.

T.Cserfalvi
Aqua-Concorde Water Analysis and Technology LLC, Budapest, Hungary

The heavy metals commonly implicated in pollution and human poisoning includes Zn, Cd, Cu, Ni, Pb, Cr and Hg. Pollution peaks in wastewater streams can come due to misoperation, temporary malfunctioning, spillout and also by a violation.

The heavy metal pollutions in sewer systems are, fortunately, accumulated in the sewage sludge remaining from urban and industrial wastewater treatment processes. Control of such polluting substances at the stage of industrial wastewater is vital since unpolluted urban sewer sludge can be used in agriculture. On the other side a havaria situation can happen when a pollution peak in the incoming wastewater stream kills the biological life in the treatment process to such extent that untreated water goes into the receiver water body for 1-3 days.

Analysis data of the sludge of municipal waste water treatment plants clearly indicate the presence or absence of industrial metal releases in a collecting area. At many areas having plating shops, pharmaceutical factories, tanneries and other chemical activities, Zn, Cd, Cu, Cr, Pb, Ni, etc. concentrations can be measured sometimes well above the relevant sludge background values, while the standard daily analysis records show that inflow waste water concentrations are always below the limits. The sampling of the sewerage system at every weekday morning, the common checking practice, is absolutely useless for discovering the sporadic waste concentrate releases which most probably happen 0.5-2 hours long during night times, weekends or holidays, but only 10-20 times in a year.

Laboratory multimetal analysis methods are not applicable at the necessary 1,500 sample / month throughput (min 50 sample / day) for long time period. The problem can only be solved by a proper analytical monitoring technique with running analysis in every 15-30 minutes, however there is no such metal monitor available for the mixed domestic and industrial waste waters having high load of fat-oil-grease (FOG) emulsion and suspended solids, both in the range of 100-1000 mg/L.

The innovative technology of ELCAD, based on a new measuring principle, makes the detection of heavy metals possible directly in raw wastewater sample. This new analytical method uses the atmospheric electrolyte cathode glow discharge atomic emission technique to monitor metal pollution peaks in wastewaters entering the treatment plant. The method detects all free and complexed metal ion forms existing at pH 1.6-1.7.

The ELCAD measuring process runs with ambient air, no mineralization or other special reagents used, only acidification by HCl to pH 1.6-1.7, requires 5-10 mL/min sample flow into the monitor during measurement.

Maintenance is required once/week for cleaning of the dicharge cell flow system and tubings (in case of high organic load), cleaning of the W anode tip. Checking and refilling of reagent bottle monthly , checking and replace of peristaltic pump tubings in 6 months.


ELCAD special features

Zn, Cd, Cu, Ni and Pb detection in ranges of 0.5 – 10 – 50 mg/L
(possible extension: Ag, Co, Fe, Mn, Al; under development : total Cr, Hg)
- no sensor surface or optical window in contact with the sample, no colloid filtering, accept grease/oil
emulsion loaded sample
- no special reagents, no bottled gases,
consumes only ~1 L/month 18 w% technical-grade HCl
- peak power consumption ~ 300 W (in idle ~ 25 W)
- 4 measurements for 5 metals/hour (3360 data /week), 6 months data record
- trigger signal for standard automatic sampler operation during pollution peaks
- fully automatic operation on 24 h/d and 7 d/w base, maintenance cycle 3-7 days 
(depending on the FOG level of the waste water)
- remote service engineer survey of operation, remote calibration
- overall running cost ~5 USD/day
- indoor installation, ~ 3 m2 footprint for instrument and accessories
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