Systems and methods are provided for intimately coupling advanced oxidation process (AOP) with biodegradation for the treatment of contaminated water. The system comprises a particulate bed having carrier particles that have a microbial film effective for biodegrading contaminants in the contaminated water. An advanced oxidation reagent is irradiated by a radiation source to provide an advanced oxidation reagent effective for oxidizing recalcitrant compounds in the contaminated water to form biodegradable byproducts. The microbial film is effective for biodegrading the byproducts substantially immediately after they are produced. The carrier particles are also effective for protecting the microbial film from the radiation and/or the recalcitrant compounds.