Techical Director Cluster Waste Water Treatment Implant


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Technology for Sustainability International Forum - Bologna 2011

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Techical Director Cluster Waste Water Treatment Implant

  1. 1. Acque del Chiampo S.p.A.ITALIAN TANNERY CLUSTER EXPERIENCE IN INTEGRATED WASTEWATER TREATMENT20 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. 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 theINTEGRATED 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 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. 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. 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/lPROBLEMS IN TANNERY WASTEWATER TREATMENT: Sludge production High quantityThe 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. 5. PROBLEMS IN TANNERY WASTEWATER TREATMENT: Odour emissionThe 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. 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. 7. ARZIGNANO WASTEWATER TREATMENT PLANT Effluent qualityParameter 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. 8. SLUDGE DISPOSAL • Bag- filling and transport • Landfill disposal • Landfill after filling and covering WATER SALINITYHides and skins are cured before transport to the tannery in order toprevent them from putrefaction. The most useful method for curing forlong-term preservation (six months) is: salting.The discharge of electrolytes into the environment has quite an impact onboth aquatic and plant life, and contamination of the watercourse by saltcan have a highly adverse effect.Another related problem with salt is that it tends to substitute mineralnutrients in soil, thus affecting intake by plants.The importance attributed to the total salt load released is dependent onthe specific environment of the site; that is, the sewage treatment plant ortype of surface water into which the tannery or the sewage treatmentplant discharges.One of the problems in Vicenza cluster is the small river where thewastewater treatment plant discharges: so it is necessary to reduce thesalinity of the wastewater.
  9. 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. 10. Thank you for the attention