Baroxymeter - Direct Toxicity Assessment of Waste Water

The Baroxymeter is a portable respirometer designed for Direct Toxicity Assessment (DTA) of waste water. DTA takes a risk-based approach to water quality analysis, using effects in biological systems as a basis for assessing likely harm to an ecosystem in water receiving effluent discharges. With DTA, an integrated assessment is made of the impact of complex mixtures of pollutants, which can usually only be partially characterised by chemical analysis. Biotest methods are usually expensive and time-consuming. The Baroxymeter is portable, reliable, accurate and gives fast results. The table below shows that the results achieved with the Baroxymeter are comparable with those obtained using a standard laboratory-based system.

Table comparing toxicity testing on the Baroxymeter and on the Strathkelvin respirometer:

Sample	Dilution	Respiration Inhibition (Baroxy meter)	Result (Baroxy meter)	Result (Strath kelvin)
1	0	0	PASS	PASS
2	0	15	PASS	PASS
3	0	100	TOXIC	TOXIC
4	1:10	0	PASS	PASS
5	0	110	TOXIC	TOXIC
6	1:10	22	PASS	PASS
7	0	0	PASS	PASS
8	0	71.5	TOXIC	TOXIC
9	1:10	4	PASS	PASS
10	0	14	PASS	PASS
11	0	73.8	TOXIC	TOXIC
12	1:10	0	PASS	PASS
13	0	93.7	TOXIC	TOXIC
14	1:10	0	PASS	PASS
15	0	0	PASS	PASS

The Principle

The Baroxymeter makes use of a harmless bacterial culture (Pseudomonas putida) which when healthy will respire, consuming oxygen and producing carbon dioxide. In the Baroxymeter test chamber carbon dioxide is absorbed using soda lime, therefore, healthy bacteria cause a measurable pressure drop as they respire. In the presence of toxic material, bacterial respiration slows down or stops, resulting in a reduced pressure change within the chamber. This is compared with a control sample and results are shown in terms of % respiration inhibition. The Baroxymeter is capable of detecting toxicity within 10 minutes.

Typical graphical display with a toxic sample

Any sample that causes ≥40% respiration inhibition is considered toxic. A sample causing 21-39% respiration inhibition is considered to be a borderline sample and it is recommended that further tests be carried out to fully characterise it. Samples causing ≤20% respiration inhibition are not considered toxic. The instrument has a traffic light LED indicator system, so for a toxic sample a red light is illuminated, for a borderline sample an amber light is illuminated and for a non-toxic sample a green light is illuminated. These thresholds can be set by the end user to comply with individual company policy.

Applications

Wastewater Treatment Plants
Industrial Effluent - heavy metals, paints, etc.
Cooling Water - from factory and industrial outlets

The Baroxymeter can also detect toxicity caused by a variety of substances including heavy metals, pesticides, insecticides and antimicrobial agents. Furthermore, field trials with major UK water companies and the UK Environment Agency have proven the versatility of the instrument and it's effectiveness as a toxicity detection tool.

Table showing toxic substances detected by the Baroxymeter

Substance	Concentration (mg/l)
Dimethoate (garden insecticide)	230*
8-Hydroxyquinoline (fungicide)	1*
Bronopol (antimicrobial agent)	55**
Copper	560**
Mercury	15**
Zinc	43**
Silver, colloidal	9**
Chromium	625**
Nickel	155**
3,5-Dichlorophenol	10**
2,4-Dichlorophenol	31**
4-Nitrophenol	42**
Formaldehyde	16**
* limit of detection     ** EC50

Advantages of the Baroxymeter

Rapid Results - Highly toxic samples are detected within 10 min.
Easy to Use - Designed to be used by a non-scientist field operative.
Portable - Lightweight durable case and in-car charger included.
Reliable - Results comparable with lab-based tests.
Cost Effective - Low-cost reagents; minimal operator time.

Product Data

• Technical Leaflet
• Comparative Trials

Online Catalogue

• Direct Toxicity Assessment (DTA)