Daniele REFOSCO Technology for Sustainability International Forum - Bologna 2011

1. Acque del Chiampo S.p.A.
ITALIAN TANNERY CLUSTER EXPERIENCE
IN INTEGRATED WASTEWATER
TREATMENT
20 Ottobre 2011- Bologna Ing. Daniele Refosco
SUMMARY
• Vicenza tanning cluster
• Acque del Chiampo S.p.A.
• Problems in tannery wastewater treatment
• Composition of wastewater
• Sludge production
• Odour emission
• Arzignano wastewater treatment plant
• Industrial wastewater line
• Municipal wastewater line
• Sludge treatment line
• Water salinity
• Conclusions

2. VICENZA TANNING CLUSTER
National turnover: 4.522 M€
Lombardy Other regions
6% 6%
Campania Venetian
10% 51%
Tuscan
27%
Incidence Venetian tannery
60
50
40
51
30
%
20
34
10
0
Italy
UE 27
ACQUE DEL CHIAMPO S.p.A.
About us…
Public owned company for the
INTEGRATED WATER MANAGEMENT (Legge Galli n. 36/94)
Employees 170
Municipalities served:
Municipal network piping 794 km
Industrial network piping 14 Km •Altissimo
•Crespadoro
Municipal network sewer pipe 471 km
•S.Pietro Mussolino
Industrial network sewer pipe 40 Km
•Nogarole Vic.no
Wastewater Treatment plant 1.500.000 + 2x 70.000 inh. •Chiampo
Analysis Laboratory 1 •Arzignano
Directly managed landfills 9 •Montorso
•Montecchio Magg.
•Brendola
•Lonigo
environmental and safety quality certificated

3. PROBLEMS IN TANNERY WASTEWATER TREATMENT:
Composition of wastewater
Wastewater from tanneries is characterized by the presence
of high concentrations of pollutants due to:
•natural organic matter from raw hides (proteins, fats,..),
15 % of the organic material is released as solids or dissolved in the
wastewater
•The use of large quantities of chemicals (up to 500 kg chemical
products/ton raw hide): the final purpose is to obtain a not-putrescent
and sellable skin in the market.
The main releases of wastewater originate from wet processing in
the beamhouse, the tanyard, and the post-tanning operations.
PROBLEMS IN TANNERY WASTEWATER TREATMENT:
Composition of wastewater
Chemicals compounds could be:
•Inorganic compounds: lime, sulfides, ammonia salts, sodium cloride,
sodium sulphite, sodium hydroxide, chromium sulphate, sulphuric acid,
etc.
•Organic compounds: amines , dicarboxylic acids, natural and syntetic
tannins , phenolic compounds, biocides compounds, fatting, dyeing,
resins, solvents, surfactans, etc.
Many chemical compounds have some toxicity if discharged into
wastewater, or they are not readily biodegradable or even not-
biodegradable
The high concentration of carbon and nitrogen compounds and
the simultaneous presence of some toxic compounds need
biological purification process treatment with high retention time
and high attention for the management.
High salinity of wastewater is another environmental impact for the
river receptor of treated wastewater

4. PROBLEMS IN TANNERY WASTEWATER TREATMENT:
Composition of wastewater
Average composition of wastewater from tanneries in Arzignano
treatment plant (year 2010)
pH 8
Sulphide (S=) 63 mg/l
Chrome (Cr3+) 79 mg/l
COD 5439 mg/l
BOD5 2241 mg/l
TKN 439 mg/l
TSS 2112 mg/l
Surfactants 104 mg/l
Chloride 2278 mg/l
Sulphate 1592 mg/l
PROBLEMS IN TANNERY WASTEWATER TREATMENT:
Sludge production
High quantity
The suspended solids content into wastewater is over 2 g/l (more
than 60% of total sludge produced from water purification)
Further sources of sludge from water purification are biological growth
and chemical sludge from final clarification
Sludge quality
depends from chemicals used in tannery process:
•high concentration of trivalent chromium (3-4%)
•some toxic substances may be present
DIFFICULT TO RECOVER

5. PROBLEMS IN TANNERY WASTEWATER TREATMENT:
Odour emission
The biggest problem is due to the release of hydrogen
sulphide gas into the atmosphere due to the presence
of high concentration of sulphide in the wastewater to
treat. Other organic volatile and smelly compounds are
present in the wastewater.
The other releases to air are due to the dry finishing
processes in the tannery.
ARZIGNANO WASTEWATER TREATMENT PLANT
Influent flow rate of industrial wastewater (by a specific sewer): 30.000 m3/d
Influent flow rate of municipal wastewater (by separated sewer): 10.000 m3/d
Tanneries connected: 160
Capacity: 1.500.000 eq. inh.
Employees: 60
Electrical power: 6.500kW
Area covered: 150.000 m2

6. ARZIGNANO WASTEWATER TREATMENT PLANT
Industrial wastewater line
• Screening and grit removal
• Equalization
- Odour treatment
• Primary sedimentation
• Biological treatment
• Sludge Flotation
• Flocculation and
final clarification
ARZIGNANO WASTEWATER TREATMENT PLANT
Municipal wastewater line
• Screening and grit removal
• Biological treatment
• Sedimentation
• Flocculation and
final clarification

7. ARZIGNANO WASTEWATER TREATMENT PLANT
Effluent quality
Parameter Average values Permit conc. YIELD BREF 2003
(2010) (mg/l) (mg/l) % %
COD 89 150 97 85-95
BOD5 <5 25 99,7 90-97
TSS 10 35 99,2 90-98
TKN 6 - 97,7 80-90
N-NH4 < 0,4 15 99,8 -
N-NO2 0,05 0,6 - N tot =92,2 -
N-NO3 13 20 - -
Cr 3+ 0,26 2 99,4 <1 (mg/l)
S -- N.R. 1 100 <1 (mg/l)
Cl - 1353 2050 -
SO4 -- 1247 1850 -
ARZIGNANO WASTEWATER TREATMENT PLANT
Sludge treatment line
• Storage and mixing
Water inside: about 95%
• Dewatering
Water inside: about 68-75%
• Drying
Water inside: about 10-15%

8. SLUDGE DISPOSAL
• Bag- filling and transport
• Landfill disposal
• Landfill after filling and covering
WATER SALINITY
Hides and skins are cured before transport to the tannery in order to
prevent them from putrefaction. The most useful method for curing for
long-term preservation (six months) is: salting.
The discharge of electrolytes into the environment has quite an impact on
both aquatic and plant life, and contamination of the watercourse by salt
can have a highly adverse effect.
Another related problem with salt is that it tends to substitute mineral
nutrients in soil, thus affecting intake by plants.
The importance attributed to the total salt load released is dependent on
the specific environment of the site; that is, the sewage treatment plant or
type of surface water into which the tannery or the sewage treatment
plant discharges.
One of the problems in Vicenza cluster is the small river where the
wastewater treatment plant discharges: so it is necessary to reduce the
salinity of the wastewater.

9. WATER SALINITY
Actions to reduce the salinity:
• Collect salt from beating in tanneries: each tannery has to beat
the raw hide before soaking
• Guidelines: all tanneries connected to the plant have to apply
in their process the best available techniques for reducing
cloride, sulphate and chromium in wastewater, contained in a
small book distribuite to every tannery
CONCLUSIONS
Our experience for minimization the
enviromnental impact from tannery wastewater
suggests:
• The wastewater treatment plant has to be flexible
(more treatment lines in parallel, availability of spare machines,
etc.)
• Careful and intensive monitoring and control of:
Tannery’s discharge
Each treatment phase in the wastewater
treatment plant
• Constant and continuous studios of innovative
treatment processes

10. Thank you for the attention