Introduction

Historically, winery wastewater has been either disposed of by obsolete and polluting methods like septic tanks/leach fields and ponds, or stored in on-site tanks and transported and treated in municipal plants. In the last few years, a number of publications have referred to the use of fixed film technologies like rotating biological contactors and fluidized beds as the most effective methods to treat winery wastewater.

Ontario is the largest wine-producer region in Canada and the fourth largest wine-producer in North America. The microclimate of the Niagara Peninsula and an effective use of biotechnology have made possible the emergence of over 110 wineries throughout the province. Most of the Canadian wineries produce less than 10 000 L/day of wastewater. The wastewater is stored in tanks and hauled to a municipal plant, stored in ponds, or discharged to leaching beds of uncertain efficiency. However, the demand for prime land, the increase in municipal fees and expansion capacity are forcing many winemakers to seek effective solutions on site. As prime vineyard land becomes more expensive, using less construction space to deal with the treatment of wastewater is becoming a technical and economic challenge. In addition, increasing both wine production and operating costs, are inducing wineries to treat their wastewater on-site.

Testing procedure

The wastewater treatment system presented here (AQUACAN^TM 6000) has been installed and tested in a well-know winery located near St. Catharines in the Niagara Region of Ontario.

Operation of the unit

A 9,540 L feed-tank was filled up with high-strength wastewater effluent from the different phases of wine production. The pH that ranged from 3.9 to 9 was adjusted to neutral values only for very acid influents. In some cases, not even pH controls were applied . The wastewater without any additional pre-treatment entered the AQUACAN^TM 6000 unit into the clarifier and the microbubble section. Next the flow moved into the RBC where BOD, TKN, and ammonia were further degraded. Steady state was achieved four weeks after the start up of the system when a biofilm layer developed on the surface of the media of the RBC. The treated wastewater was pumped to the collector tank (Figure 1). As the water went through the ABC unit, samples of water were collected at the inlet and outlet of the unit. These samples were taken and analyzed for BOD, TSS, TKN, TP, NH3, pH, DO and temperature.

Table 1 exhibits the ranges and average concentrations of the influent treated. To achieve consistently high removal in the absence of virtually any pre-treatment or pos-treatment confirms the robustness of the process. Indeed, the addition of another unit in series or a polishing stage will produce an effluent capable of meeting the stringent criteria applied to tertiary treatment for discharge to surface waters.

Table 1. Wastewater Characteristics

Figure 1. Full-scale equipment used in the test

Results

Organic matter removal

A graph of the % BOD removal versus organic load is shown in Figure 2. For a load of 290 g/m³day or less, corresponding to an average BOD in the influent of 2,500 mg/L, the removal was greater than 97 %. That figure did not vary much for loads as high as 1000 g/m³day corresponding to influent BOD of 2500 mg/L. As the loading increases, the BOD and CBOD removal decrease. At an extremely high organic loading of more than 11,500 g/m³day corresponding to a BOD of 27, 000 mg/L, over 70 % of BOD and CBOD were removed.

Figure 3 shows the performance of one of the units in November and December 2003. Curves of the variation of the influent and effluent show three periods. The first goes from Nov. 5 to Nov. 19 where the % removal ranges between 92 % and 98 %.

Figure 2. BOD and CBOD Removal Vs. Organic Load (g/m³ day)

After that period, high strength wastewater with a BOD of up to 27 000 mg/L is fed to the treatment unit. On November 2, the unit experienced an accidental toxic shock as a result of cleaning the winery steel tanks with bleach (calcium hypochlorite (HTH)). The exceedingly high concentration of chlorine partly destroyed the normal growth of the biofilm and the BOD removal was insignificant. The result of the impact of the bleach on the biofilm is shown in Figure 3, and lasts from Dec. 2 to Dec. 12, 2003. In those 10 days, the unit performance was severely affected. The biofilm and normal operation of the unit was re-established very fast, and from Dec. 12, 2003 to the end of December 2003, the unit recovered its steady state performance removing an average of 93 % of BOD and CBOD.

Figure 3. BOD and CBOD Removal Performance

Total suspended solids removal

Figure 4 shows the TSS concentrations measured at the inlet and outlet of the ABC for the entire testing period. From this figure, it can be seen that between Nov. 12 and Dec. 16, 2003, the TSS at the outlet increased coinciding with the toxic discharge. Previous to the toxic discharge, there is a sharp increase in the organic load. These results are related with the results observed in Figure 3 where the BOD and CBOD removals decreased as a result of the toxic shock and the high organic load occurred in the same period. The performance of the unit is summarized in Table 2.

Table 2. Performance Summary

Figure 4. TSS Concentration at the Inlet and Outlet of the Testing Period.

Conclusions

An Active Biological Contactor (ABC) manufactured as AQUACAN^TM by Water Purification Technologies has been tested with high strength winery wastewater. These are the most relevant conclusions:

1. The unit can successfully treat high strength winery wastewater in modular compact units. Expenses for operation and maintenance were very low. The capital cost of the units is lower than that of equivalent conventional technologies like aeration ponds and activated sludge for comparable treatment.
2. The flow rate treated ranged from 500 to 3600 L/day, the pH range was 3.9 to 9, the BOD5 from 640 to 12 000 mg/L and the Total Suspended Solids (TSS) from 432 to 6340 mg/L. The analyses of the effluent indicate that without any pre- or post-treatment the unit removed 95.5 % of BOD5, and 86.8 % of TSS.
3. The superior performance of the ABC and its rapid recovery from toxic shocks is attributed to the interfacial area of the RBC disks 50 % larger than that found in commercial RBCs.
4. Two independent treatment processes act as a back up for each other thus ensuring a protection against an unexpected breakdown of the unit.
5. The technology has been evaluated and the present performance claims confirmed by the Ontario Ministry of the Environment (MOE) and the Canadian Ministry of the Environment.