The dairy industry produces yogurts, cheese, ice-cream and butter in addition to milk, and dairy industry waste generated by these processes must be treated.
The residues produced during these transformation processes, combined with large water consumption needs means that the dairy industry produces a lot of wastewater; 4 – 15 L of water can be used per litter of milk processed.
Wastewater is produced during the cleaning process of the milking equipment and pipelines that are usually made in four cycles: 1) rinsing, where about 92% of the suspended solids are removed; 2) detergent wash to remove the attached organic material; 3) acid rinsing to remove the inorganic deposits from the piping and neutralise the alkaline detergent residue; 4) sanitising rinse to ensure that the milk lines are free of any microorganisms.
Dairy industry waste water contains lots of organic matter and hydrocarbon compounds, presenting high values of chemical oxygen demand, COD (1000–12 000 mg O2/L,) and biochemical oxygen demand, BOD5 (500–2600 mg O2/L). This makes the use of biological processes for the treatment of these effluents a very good choice.
Wastewater with high levels of organic matter (COD/BOD) Phosphorus (P) and Nitrogen (N) cause several problems, such as eutrophication, oxygen consumption and toxicity, when discharged to the environment. It is, therefore, necessary to remove these substances from wastewaters to reduce their harm to environments. It is also a legal requirement!
The treatment of dairy industry waste water by biological purification processes, using biofilms, has many advantages in terms of capital investment, operating costs and efficiency compared to other process.
Two technologies are commonly used for biological treatment of waste water: activated sludge and trickling filters. A moving bed biological reactor (MBBR) is a compilation of these two technologies. The biomass in the MBBR exists in two forms: suspended flocks and a biofilm attached to carriers / a substrate. It can be operated at high organic loads as it doesn’t tend to get overloaded.
Further reading on biofilms and dairy waste
Andreia D. Santos, Rui C. Martins, Rosa M. Quinta-Ferreira, Luis M. Castro,
Moving bed biofilm reactor (MBBR) for dairy wastewater treatment, Energy Reports, Volume 6, Supplement 8, 2020, Pages 340-344, ISSN 2352-4847, https://doi.org/10.1016/j.egyr.2020.11.158.
A. Aitcheikh, N. Boutaleb, B. Bahlaouan1, A. El Jaafari,T. Taiek, M. Bennani, S. Lazar,S. El Antri. Dairy Wastewater Treatment in Moving Bed Biofilm Reactor using Sardine’s Scales as Biomass Support. International Journal of Engineering Research & Technology (IJERT), Vol. 3 Issue 11, November-2014. https://www.ijert.org/research/dairy-wastewater-treatment-in-moving-bed-biofilm-reactor-using-sardines-scales-as-biomass-support-IJERTV3IS110126.pdf
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