Wastewater treatment in the ham industry

• 1. Effluents in the meat and ham industry.
• 2. Treatment study in Sigmalab laboratory.
  2.1. Description of the effluent.
  2.2. Physical-Chemical Treatment: Coagulation-Flocculation Tests.
  2.3. Analytical results
• 3. Conclusions

1. Effluents in the meat and ham industry.

There is a wide variety of industries within the meat industry: slaughterhouses for different types of animals, meat processing plants, ham processing plants, fresh, cooked or precooked products, and so on.

One of the industries of great interest is ham processing, which tends to have variable production peaks depending on the time of year (demand for hams generally increases considerably towards the end of the year). Its composition is not as raw as that found in slaughterhouse effluent, but mainly contains fats, oils, pre-processed organic matter, high levels of suspended solids, and salts susceptible to precipitation, such as hydroxides.

The treatment of these effluents generally includes the following steps:

• Pre-treatment by coagulation-flocculation and DAF flotation.
• Biological treatment system MBR type biological treatment system .
• Desalination and polishing by means of membranes and/or advanced technologies.

There is an article that describes in more detail the generation of wastewater in the meat industry and all possible treatment methods.

This post details the tests conducted at the SIGMADAF laboratory for the treatment of effluent from a client in the meat industry, specifically for its ham processing plant. The results are very promising and demonstrate the high efficiency of the physicochemical pretreatment process—coagulation-flocculation combined with DAF—for this type of effluent.

2. Treatment study at the Sigmalab laboratory

Laboratory-scale tests and studies allow the identification of specific chemicals for effluent treatment, the doses and the hydraulic residence times required for each reaction. The analysis of the clarified products allows to establish the purification performance that can be achieved.

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Description of the effluent

We work with water from a ham processing plant of a large meat industry. Daily composite samples are received and a proportional sample is made up to work in the laboratory, which is mixed according to the indications of the daily and weekly production distribution given by the client.

The samples have a whitish, milky appearance with a characteristic fatty odor. Some samples contain fat clots, and are shaken vigorously before mixing to achieve complete homogenization.

The pH of the samples is slightly acidic, with a value of 6.

Figure 1. Daily effluent samples from a ham processing plant.

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2.2. Physical-Chemical Treatment: Coagulation-Flocculation Tests

The separation and removal of oils and fats, chemical oxygen demand (COD), total suspended solids (TSS), and turbidity are evaluated using a physicochemical coagulation-flocculation treatment process with DAF flotation.

Different products from various manufacturers are tested, varying types, combinations and doses. The correct types of chemicals are identified and their information is shown in Table 1.

Table 1. Information on the products used in the coagulation-flocculation tests.

Type of product	Abbreviation	Active compound
Adsorbent and emulsion breaker		Activated carbon
Coagulant	PAC	Aluminum polychloride with aluminum-hydroxide-chlorine salts
Flocculant		Cationic polyelectrolyte with very high charge density
Base	NaOH	Sodium hydroxide for pH adjustment

Of the combinations tested in the laboratory, the one that gave the most efficient solid and liquid phase separation results is described in this article.

It requires the first application of a specific product for fats and oils: an adsorbent with emulsion-breaking effect. These products are generally powders or granules of activated carbon or other materials (in this case, activated carbon), which must be prepared in suspension or dissolution (depending on the type of product). For this case, ~200 ppm of adsorbent, prepared in suspension, is applied.

Next, coagulation is carried out with ~1000ppm (laboratory excess dose) of PAC with aluminum-hydroxide-chloride salts, generating clots of solids. These coagulants increase the acidity of the medium, i.e. the pH decreases, so a pH adjustment step is necessary.

The pH adjustment with NaOH is the most appropriate and in this case ~300ppm soda is used. Bringing the pH above neutrality, towards slightly alkaline values, close to 8, hydroxide precipitation occurs, which contributes to the elimination of the substances that precipitate bound to them and become part of the clots already generated. Water is highly sensitive to the addition of soda, so careful control of pH and soda dosage should be considered at the plant scale.

Finally, a flocculant is applied to agglomerate the clots into larger flocs, in this case a very highly charged cationic polyelectrolyte is used (as explained in the reference article, the substances in meat industry effluents are negatively charged, so positively charged chemicals must be used for their separation). The dose is ~8ppm.

All the steps described above require a high contact time each, which translates at plant scale into a high hydraulic residence time.

The result is shown in Figure 2. This process allows obtaining a clear clarified product and a consistent and light floc that tends to float.

Figure 2. Result of applying the described chemicals to the sample: Clear supernatant and consistent, light flocs.

2.3. Analytical results

The composite sample and the clarified from the test are analyzed for oils and fats, COD, TSS and turbidity values and the treatment performance is calculated. The analytical results are shown in Table 2.

Table 2. Analytical results of the tests carried out with the effluent from the ham industry.

Parameter	You.	Composite sample	Clarified	Elimination performance
AyG	mg/L	460	26,6	94,2%
COD	mg/L	3750	416	88,9%
SST	mg/L	1510	9,2	99,4%
NTU	NTU	1260	5,49	99,6%
pH	-	6	8

The removal of pollutants is very high performance: removal of 94.2% of Oils and Fats; 88.9% of COD; 99.4% of TSS and a clarified with 5.49 NTU of turbidity.

3. Conclusions

• Effluents from the ham industry contain mainly fats, oils, pre-processed organic matter, high content of suspended solids and salts susceptible to precipitation as hydroxides.

• This study demonstrates the high efficiency of the physicochemical coagulation-flocculation treatment using a DAF for effluents from the meat industry, specifically from ham processing plants.

• The removal of pollutants is very high performance: removal of 94.2% of Oils and Fats; 88.9% of COD; 99.4% of TSS and a clarified with 5.49 NTU of turbidity.

• Las dosis que a escala de laboratorio resultaron efectivas, con los rendimientos indicados para este tratamiento fueron: ~200ppm de adsorbente y rompedor de emulsión más ~1000ppm de coagulante PAC más <300ppm de sosa más ~8ppm de floculante catiónico.