Wastewater treatment apparatus to achieve class B biosolids using chlorine dioxide

A wastewater treatment system comprising:

• a headworks for receiving raw sewage wastewater having biosolids;
• a biological treatment station that is in fluid communication with said headworks;
• a clarifier in fluid communication with the headworks for concentrating biosolids from the raw sewage wastewater, wherein upon being subject to the biological treatment station and clarifier, the wastewater is converted to waste activated sludge (WAS) having a targeted biosolids content;
• a dewatering device having an inlet;
• a first conduit for transporting WAS away from the clarifier and directly from the clarifier into the inlet of the dewatering device and comprising an oxidant treatment zone downstream of the clarifier and upstream of the inlet of the dewatering device;
• and
• a chemical oxidant feed device in fluid communication with said first conduit so as to dose chemical oxidant and said oxidant treatment zone, wherein upon being subjected to oxidation in the oxidant treatment zone the WAS is converted into a treated biosolid sample,
• wherein said targeted biosolids content is 0.5-5 weight percent of the WAS.

A method of treating primary wastewater to produce Class B biosolids, the method comprising:

• subjecting the primary wastewater to anaerobic or aerobic digestion to produce digested sludge;
• introducing the digested sludge into a clarifier configured to produce a concentrated digested sludge from the digested sludge and to output the concentrated digested sludge through an outlet of the clarifier;
• and
• subjecting the concentrated digested sludge to dosing of chemical oxidant in a treatment zone through which the concentrated digested sludge flows directly from the outlet of the clarifier and into an inlet of a dewatering device, the treatment zone being downstream of the outlet of the clarifier and upstream of the inlet of the dewatering device, wherein the dosing achieves a dose rate between 25 and 200 parts per million in the concentrated digested sludge in the treatment zone and substantially complete mixing of the oxidant within 30 seconds of dose delivery in the treatment zone;
• wherein the primary wastewater is not subjected to biological treatment prior to becoming digested sludge.