at 08H30 | 520 CF

Leveraging Wastewater and Sludge

Moderated by: Adrian Toth, CWWA
Green and circular economy

- Phosphorus Recovery from Iron Phosphate in Municipal Wastewater Solids as Useful Phosphate Rock

It is no secret, phosphorus has caused many headaches for environmentalist, engineers and biologists. A common issue is blue-green algae and can have severe consequences. Often, phosphorus is present as phosphate. Dissolved phosphate flows to and concentrates in municipal wastewater treatment plants. From there, iron chloride is added to precipitate out of the aqueous phase into solids. These solids are sent then sent to waste or sold as fertilizer, also called biosolids. Unfortunately, the phosphate present in these solids cannot be assimilated by plants. This novel process aims to transform phosphate into carbonate apatite, which can then be up-taken by plants. Ultimately this solution aims to solve some sustainability issues, as well as ensure food security.

- Filter backwash recycling from a drinking water membrane filtration process

Backwash recycling from filters is a common practice in many drinking water treatment plants in the USA, but it is still not widely applied North of the border. Recirculating backwash water allows reducing the raw water withdrawals from the natural environment and minimizing the wastewater discharges to the sewer and receiving bodies. Filter backwash water will be recirculated in the Lac-à-la-Pêche drinking water treatment plant in Shawinigan by adding a secondary treatment consisting of equalization, chemical addition, lamellar settling and sludge thickening and dewatering. The results from a pilot plant trial conducted during the design of the treatment plant will be presented in this conference, giving a better insight of the technical and regulatory challenges that filter backwash recycling poses in the context of drinking water production.

- Anaerobic Digestion at 20°C with Ozonation to Minimize Waste Biosolids and Maximize Energy Recovery from Wastewater

Biosolids disposal from wastewater treatment can account for 50% of operation budget. Anaerobic digestion of waste activated sludge (WAS) can reduce production and recover energy. However, slow hydrolysis imposes the operation of digesters at or above 35 °C to maintain residence times around 20 days, which implies significant energy expenditures. Here, we demonstrate at lab-scale (1 to 4 L) and pilot-scale (300 L) that ozonation of WAS enhances its conversion to methane at 35 °C. Furthermore, lab-scale experiments revealed the possibility to operate digesters at 20 °C while keeping a 20-day SRT and achieving higher volatile suspended solids (VSS) destruction and CH4 production than for a conventional 35°C digesters. Therefore, combining WAS ozonation/20 °C-anaerobic digestion system can improve the net energy recovery over a conventional system. Process scale-up and complete elimination of heating are the new R&D goals to improve the sustainability of biosolids management.