| Trickling Filter | Municipal wastewater, food-processing wastewater, and biodegradable industrial wastewater | Approximately 0.5–3.0 m³/m²·h, depending on media and design | Install a distribution system, underdrain, ventilation path, drainage channel, and recirculation pipe where required. Provide protection against freezing and excessive sunlight where applicable. | Maintain uniform wetting, sufficient dissolved oxygen, stable flow distribution, and suitable pH. Keep influent solids low enough to prevent media blockage. | Inspect spray nozzles and distributor arms regularly; remove accumulated solids; flush underdrains; check ventilation and recirculation equipment. | Simple operation, low energy demand, and good resistance to moderate hydraulic variations | Requires relatively large land area and effective odor, fly, and clogging control |
| Moving Bed Biofilm Reactor (MBBR) | Carbon removal, nitrification, and biological polishing of municipal or industrial wastewater | Commonly designed by reactor volume and media fill fraction; media fill is often about 40–70% of reactor volume | Provide aeration grids or mixing equipment, media-retention screens, access covers, influent screening, and sufficient freeboard to contain media. | Maintain adequate mixing and dissolved oxygen. Typical aerobic operation often uses about 2–4 mg/L dissolved oxygen, subject to process design. Prevent media escape and excessive foam. | Clean or inspect retention screens, verify blower and diffuser performance, check media distribution, and remove settled grit or excess sludge. | Compact footprint, flexible capacity, and good tolerance of load changes | Needs continuous mixing or aeration and reliable screen maintenance |
| Submerged Aerated Biofilter (BAF) | Tertiary or advanced biological treatment, including carbon removal and nitrification | Often approximately 2–10 m³/m²·h, subject to media type, loading, and effluent target | Install a pressure-resistant or open filter vessel, air distribution system, backwash piping, treated-water outlet, and suitable instrumentation. | Control filtration velocity, air rate, dissolved oxygen, pH, and head loss. Maintain a stable backwash trigger based on pressure loss or effluent quality. | Perform periodic air scour and water backwash; inspect valves, blowers, diffusers, and media condition; dispose of backwash water properly. | High treatment efficiency and small footprint | Higher operating complexity and energy consumption than passive biofilters |
| Rotating Biological Contactor (RBC) | Small- to medium-scale municipal wastewater and low-to-moderate strength biodegradable wastewater | Design is generally based on protected media surface area and organic or ammonia loading rather than only hydraulic flow | Provide a covered or protected tank, shaft supports, drive equipment, primary screening, ventilation, and access for mechanical inspection. | Maintain steady rotation, suitable submergence, adequate oxygen transfer, and protection from shock loads, grease, and abrasive solids. | Inspect shafts, bearings, couplings, motor, discs, and tank levels; remove grease and solids; monitor vibration and rotational speed. | Moderate energy use and relatively straightforward biological control | Mechanical components require protection and may be vulnerable to torque, corrosion, or uneven loading |
| Submerged Fixed-Bed Biofilter | Ammonia oxidation, organic matter removal, and polishing after primary or secondary treatment | Commonly approximately 1–5 m³/m²·h, depending on media porosity and treatment objective | Use a robust support structure, evenly distributed influent, air or water backwash system, access ports, and adequate pretreatment for suspended solids. | Maintain adequate oxygen, flow distribution, pH, alkalinity for nitrification, and acceptable head loss. Avoid toxic or inhibitory influent concentrations. | Backwash according to head loss and effluent quality; inspect media support and air headers; remove accumulated solids and verify flow paths. | Stable biofilm retention and efficient use of reactor volume | More susceptible to clogging if pretreatment and backwashing are inadequate |
| Constructed Wetland Biofilter | Rural wastewater, decentralized treatment, stormwater polishing, and low-flow applications | Hydraulic loading is site-specific; commonly about 0.02–0.20 m³/m²·d for many subsurface-flow designs | Provide an impermeable liner, graded filter media, inlet and outlet distribution, drainage control, vegetation plan, and sufficient land area. | Maintain proper water levels, prevent short-circuiting, control invasive plants, and protect the bed from excessive solids and hydraulic surges. | Remove weeds and accumulated debris, inspect embankments and liners, control mosquitoes where necessary, and maintain inlet and outlet structures. | Low energy demand, natural appearance, and simple routine operation | Large land requirement and seasonal performance variation |
| High-Rate Biofilter with Granular Media | Compact biological polishing, nitrification, and removal of residual biodegradable organic matter | Typically designed using media-specific surface area, biological loading, and allowable head loss; hydraulic rates vary widely | Provide a suitable filter vessel, media-retention layer, air and water backwash systems, drainage, instrumentation, and reliable pretreatment. | Monitor head loss, dissolved oxygen, ammonia, nitrate, pH, temperature, and effluent turbidity. Maintain consistent filtration and backwash cycles. | Backwash on a planned or demand-based schedule; inspect media loss, valves, underdrains, air scour, and backwash-water handling. | Very compact design and strong polishing capability | Requires accurate control, skilled operation, and dependable backwash equipment |
