Water purification techniques

General

Flow or composition variation [?]
Are there significant variations in flow or composition in wastewater to treat? These can occur over a short (1 hour) or a longer period (day-week)
- Eg.1: short period: the continuous flow of waste water is daily disturbed by sudden peak discharge of cleaning water during the evening shift.
- Eg.2: long period: the production department is working around the clock in a five-day system with a continuous flow of waste water. During the weekend only cleaning occur with much smaller wastewater streams of a different composition.
yes
no
Separability [?]
Can the suspended solids be separated easily from the waste water; this means, in case of a standstill of the wastewater: do they form a floating layer at the top or do they sink to the bottom?
good
bad
pH [?]
Is the degree of acidity (pH) of the waste water clearly within the limits between (5-8), or it is regularly above 8 or below 5.
pH < 5
5 <= pH < 8
pH >= 8
Settleability [?]
Do the floating substances sink to the bottom under the influence of the force of gravity when the waste water is standing still for some time?
good
bad
Temperature [°C] [?]
Indicate 'yes' if temperature remains below the specified value, in other cases, indicate 'no'.
T <= 50
T > 50
Removing total plate count [?]
The total plate count is an indication of the number of micro-organisms present in the waste water. If pathogenic (disease causing) microorganisms are present and if it is desired to get a disinfected effluent, it is necessary to indicate that the total plate count is to be removed.
yes
no
Suspended solids [mg/l] [?]
Suspended solids (SS) are all non-dissolved substances in a certain volume of waste water. In principle, the floating components are defined as those particles that can be separated by filtration or centrifugation. The result is expressed in mg/l.
<= 500
> 500
No extensive removal [?]
For this parameter, indicate 'yes' if any of the following pollutants should be extensively removed. This information is determent whether or not technique 'small-scale wastewater purification' will be selected.
yes
no
Removing suspended solids
yes
extensively
no

interfering substances

Oil or grease of organic origin [?]
Are oil or grease systematically detected in the waste water? When taking a sample of the waste water and when keep it for a while adjusting to the ambient temperature, does a liquid or solid floating layer arise?
>100
<=100
Coarse particles [?]
Is there a risk that coarse particles (> 20 mm) occur in the waste water? Coarse particles are eg. wood, bottles, glass, etc. The removal of these particles is necessary to protect the provided downstream waste water treatment installation.
present
not present
Removing grease or oil of biological origin
yes
extensively
no
Sand [?]
Is sand systematically detected in the wastewater? Sand can eg. end up in the waste water through drainage of industrial sites connected to the waste water circuit.
present
not present
Mineral oil [mg/l] [?]
The content of mineral oils can be determined by means of extraction with CCl4. It is expressed in mg/l.
present
not present
Emulsion [?]
Is an emulsion systematically detected in the waste water? Emulsions give waste water a cloudy view.
present
not present
Removing mineral oil
yes
extensively
no

organic compounds

BOD [mg O2/l] [?]
BOD < 150
150 <= BOD < 300
BOD>=300
VOC [mg/l] [?]
VOC stands for volatile organic halogen compounds. These pollutants may be toxic for the micro-organisms in a biological treatment installation. In that case, they may seriously disturb the purification. The toxicity is very much dependent on specific component - further research is needed.
<= 10
> 10
Removing BOD
yes
extensively
no
Removing VOC
yes
extensively
no
COD [mg O2/l) [?]
COD stands for chemical oxygen demand. The COD is determined by the aid of potassium dichromate, so most organic compounds are largely oxidized. COD is a measure for the oxidisable contamination of the water and is expressed in mg O2/l. COD is almost always higher than BOD.
<2000
> 2000
VOC toxic
no
yes
Removing COD
yes
extensively
no
BTEX [mg/l] [?]
BTEX include the aromatic hydrocarbons benzene, toluene, ethyl benzene and xylene. These pollutants can be toxic for the micro-organisms in a biological treatment installation. In that case, they may seriously disturb the purification. The toxicity is very much dependent on specific component - further research is needed.
<= 10
> 10
COD/BOD [?]
This ratio determines the biodegradability of the organic material present. The lower, the more easily biodegradable. If the ratio is higher than 5, a further post-treatment for removing COD after the biological treatment is required.
COD/BOD <= 5
> 5
Removing BTEX
yes
extensively
no
PAHs [mg/l] [?]
PAH stands for polyaromatic hydrocarbons. These pollutants may be toxic for the micro-organisms in a biological treatment installation. In that case, they may seriously disturb the purification. The toxicity is very much dependent on specific component - further research is needed.
<= 1
> 1
BTEX toxic
yes
no
Removing PAHs
yes
extensively
no
Persistent organic pollutants toxic [?]
Persistent organic pollutants are organic compounds that are not or very poorly biodegradable. They are commonly found in pesticides, biocides, detergents and anti foam. Is there a risk that these substances occur in the waste water? For example, when in the production process vegetables are rinsed, the rinsing water can contain pesticides. If this rinse water is treated as waste water, these substances can interfere with any biological treatment.
yes
no
PAHs toxic
yes
no
Removing persistent organic pollutant
yes
no
extensively
Removing AOX / EOX [?]
AOX stands for adsorbable halogenated compounds, EOX for extractable halogenated compounds. These pollutants can be toxic to biological treatment installation so they can seriously disrupt the purification. The toxicity is very much dependent on specific components - further research is needed.
yes
extensively
no
AOX / EOX toxic
yes
no

nutrients

BOD/N [?]
This ratio determines the extent to which the micro-organisms in a conventional activated sludge treatment system (organic), are able to remove nitrogen. N stands for the total nitrogen content (in mg/l). A value under 20 indicates that a conventional biological treatment alone is not sufficient to remove nitrogen.
<20
>=20
Removing NO3- [?]
NO3 - nitrate nitrogen.
yes
extensively
no
Removing Kj.N
yes
no
Removing NO2- [?]
NO2 - nitrite nitrogen.
yes
extensively
no
NH4+ [mg/l] [?]
NH4+ - ammonium nitrogen.
<= 500
> 500
BOD/PO4-3 [?]
This ratio determines the extent to which the micro-organisms in a conventional activated sludge treatment system (organic), are able to remove phosphate. A value below 50 indicates that a conventional biological treatment alone is not sufficient to remove phosphate.
< 50
>= 50
Removing NH4+
yes
extensively
no
Removing (ortho-)PO4-3 [?]
ortho) PO 4 3- - (orthophosphate
yes
extensively
no

metals

Removing metals
yes
extensively
no
Removing Cr (VI) [?]
Cr (VI) - hexavalent chromium. The pollutant may be toxic to the micro-organisms in a biological treatment installation. In this case, Cr (VI) seriously disrupt the purification. The toxicity may occur if the concentration is greater than 5 mg/l.
yes
extensively
no
Metals toxic
yes
no
Cr(VI) toxic (> 5 mg/l) [?]
Cr (VI) (chromium - hexavalent) is expressed in mg/l.

Additional information:

This pollutant can be toxic to biological treatment installations, so it can be seriously disrupted. The toxicity may occur if the concentration is greater than 5 mg/l.
yes
no
Recovering metals
yes
no

inorganic salts

Removing CN-
yes
extensively
no
Removing S-2
yes
extensively
no
CN- toxic (> 1mg/l)
yes
no
S-2 toxic [?]
A high concentration of sulphide (S2-)can be toxic to the micro-organisms in a biological treatment installation. Purification can become seriously disrupted.
yes
no
Removing SO4-2
yes
extensively
no
Removing F-
yes
extensively
no
SO4-2 toxic [?]
A high concentration of sulphate (SO42-)can be toxic to the micro-organisms in a biological treatment installation. Purification can become seriously disrupted.
yes
no
F- toxic [?]
A high concentration of fluoride (F-)can be toxic to the micro-organisms in a biological treatment installation. Purification can become seriously disrupted.
yes
no
Removing Cl-
yes
extensively
no
Removing total salt content
yes
extensively
no

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