The production activity in the food company generates wastewater and processed directly to municipal drains. Montreal municipal regulations require companies to respect actual standards regarding the following physicochemical parameters: pH, Temperature, Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), Oil and Grease, and Mineral Oil and Grease. Despite the continuous efforts of the company to treat wastewater (source reduction, grease trap, etc.), several critical parameters remain out of control and don’t comply with targets fixed by the municipal standards. Thus, the objective of this project is to study and evaluate the efficiency of different existent methods for wastewater treatment in a specific industrial context. Through a methodology based on different steps, different methods are tested. The manufacturing site is divided into two different production zones: “Zone 1” and “Zone 2”. Each zone is characterized by a specific type of production and générâtes wastewater. Wastewater is processed to two major grease traps located outside the plant. Indeed, wastewater of Zone 1 is processed to the drain located before “Grease trap 1” through a completely independent sewerage system from zone 2. On the other hand, wastewater from zone 2 is processed to “Grease trap 2”. In this study, we investigate the improvement of the following parameters: pH, COD, TSS, Oil and Grease and Mineral Oil and Grease.
The pH became homogeneous and registers a value of 7 after installing the aerator (phase 3). Furthermore, during phase 4 (dissolved air flotation); we note that the flotation has no effect on pH. Finally, the results obtained in phase 5 and 6 (use of UF and NF membranes) on pH demonstrate that the use of UF and NF membranes makes it more acid. Indeed, the pH decreases from 6.2 to 3.4 with the use UF membrane for zone 1. Similarly, the pH decreases from 9.8 to 8.9 with the use NF membrane in zone 2.
The concentration of COD is reduced after fixing the Sieve and reach 916 mg/L in zone 1 and up to de 956 mg/L in zone 2 (Phase 2). Adding an aerator (Phase 3) increased the efficiency to reduce the concentration of COD to 515 mg/L at “Grease trap 2”. This result respects the standard value which is equal to 800 mg/L. The analysis using a sieve and dissolved air flotation reduce the COD to reach 782 mg/L in zone 1 and up to 2181 mg/L in zone 2. The membrane separation processes reduce the COD to reach 960 mg/L with the use of UF membrane and 480 mg/L with the use of NF membrane in Zone 1. For Zone 2, COD is reduced to achieve 2158 mg/L with the use of UF membrane and 624 mg/L with the combination of UF and NF membranes. So using a NF membrane is the most effective method for COD treatment in this case, and guarantees the lowest rate and compliance with municipal standards for both zones.
In phase 1, the Oil and Grease is about 1480 mg/L in Zone 1 (10 times more than the standard) and 2888 mg/L in zone 2 (20 times more than the standard). Although the use of grease trap, draining, sieve, aerator, flotation and UF membrane separation contribute to reduce significantly the Oil and Grease rate, it remains above the standard. However, with the use of NF membrane separation, the Oil and Grease is reduced and reach the value of 149 mg/L at zone 1 and up to 7 mg/L at zone 2. For both zones, the results comply with municipal standards.
For the Total Suspended Solids (TSS), the use of grease trap with monthly drain reduces TSS values to reach 261 mg/L at grease trap 1 which respects the standard (500 mg/L). The TSS value reaches 322 mg/L at Grease trap 2. With the presence of Sieve (phase 2), the TSS reaches a value of 50 mg/ L with Draining +Sieve at grease trap 1, and a value of 79 mg/L at grease trap 2. Using the dissolved air flotation method (Phase 4), the MES rates for zone 1 has reached the value of 252 mg/L and a value of 1098 mg/L in zone 2 , with a percentage of 100% water pressure. Finally, with membrane filtration (phases 5 and 6), the TSS rate is almost equal zero in zone 1 (complete removal of suspended solids). However, the value of TSS is only reduced to 262 mg/L in zone 2 but with respect to the standard (500 mg/L). Regarding the VSS, it has a similar behavior to the TSS rate.
During this project, the different phases of analyzes have identified the potential of each method of treatment. Certainly the combination of pretreatment method of sieve + ventilation with the method of treatment with membrane filtration UF + NF can meet the regulatory requirements for physicochemical parameters studied. To ensure with certainty the results, further studies are necessary and possible to test these methods in light of changes in water characteristics of zones 1 and 2 in a more representative horizon (hourly, daily, week, month, etc. ) this will help detect critical periods in the most polluted discharges wastewater.
| Date | 25 Oct 2016 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Frédéric Monette (Supervisor) |
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