Biological deodorization filtration pond

▍ Working principle

The purification process of a biofilter is a complex biological oxidation process, which can be divided into three continuous stages:

1. Mass Transfer and Dissolution Stage (Gas-Liquid Contact):

● Pre-wetted and conditioned waste gas is evenly distributed to the bottom of the biofilter bed through a gas distribution system.

● Odorous pollutants in the waste gas (such as H₂S, NH₃, thiols, VOCs, etc.) diffuse from the bulk gas phase into the water film (biofilm) covering the filter media surface and dissolve in the water.

2. Adsorption and Absorption Stage (Liquid-Solid Contact):

● Pollutant molecules dissolved in the water further diffuse from the aqueous phase to the surface of the biofilm formed by microorganisms, where they are adsorbed and captured by the microorganisms and their secreted extracellular polymers.

3. Biodegradation Stage (Core Reaction):

● Obligate microorganisms (including bacteria, fungi, actinomycetes, etc.) attached to the filter media use the adsorbed pollutants as a carbon source and energy source for their growth and reproduction.

● Microorganisms completely decompose and metabolize malodorous substances through their life activities (oxidation, synthesis, and decomposition), ultimately transforming them into harmless or low-harm simple substances such as CO₂, H₂O, SO₄²⁻, and NO₃⁻.

● Simplified reaction formulas (using H₂S and NH₃ as examples):

● H₂S + 2O₂ → H₂SO₄ + Energy (Sulfur-oxidizing bacteria)

● NH₃ + 2O₂ → HNO₃ + H₂O + Energy (Nitrifying bacteria)

▍ Structural features

1. Rectangular PP Housing:

● Corrosion Resistant and Long-Lasting: PP material perfectly resists corrosion from acidic or alkaline environments (such as H₂SO₄, HNO₃) and humid environments caused by microbial metabolism, resulting in a service life far exceeding that of concrete or carbon steel.

● Lightweight and High-Strength: The equipment is lightweight, suitable for rooftop installation or sites with limited foundation bearing capacity, facilitating transportation and installation.

● Flexible Design: The square structure facilitates modular design and parallel combination, allowing for flexible capacity expansion according to the air volume processed, resulting in a compact space layout.

2. Highly Efficient and Uniform Air Distribution System:

● Located at the bottom of the filter bed, it consists of main and branch pipes made of PP or HDPE material, with precisely calculated air distribution holes on the branch pipes.

● Ensures that exhaust gas passes uniformly across the entire cross-section of the filter bed with low resistance and low velocity, avoiding airflow short-circuiting and guaranteeing filter media utilization and purification efficiency.

3. Biological Filter Media Layer (Core Medium):

● The filter media serves as the carrier for microbial attachment and growth, typically employing a mixture of organic and inorganic materials (such as compost, bark, perlite, and inert ceramic particles).

● It requires good water retention (to provide moisture for microorganisms), permeability (to ensure smooth airflow and oxygen supply), buffering capacity (to stabilize pH), and nutrient availability (to provide initial nutrients for microorganisms).

4. Spray Humidification System:

● Composed of a water pump, PP pipes, and nozzles, it periodically or continuously sprays water mist onto the top of the filter bed.

● Core Function: Maintaining suitable humidity (typically 40%-60%) in the filter media is a prerequisite for microbial survival and metabolic reactions. It also regulates the filter bed temperature and replenishes water consumed by metabolic reactions.

5. Monitoring and Control System:

● Equipped with a level gauge, pH meter, and temperature sensor to monitor the health status of the filter bed.

● Can be equipped with an automatic control system to automatically start and stop the spray based on the filter media humidity, achieving intelligent operation.

▍ Core advantages

● Highly Efficient and Thorough Purification: Pollutants are completely decomposed into harmless substances, rather than simply transferred, eliminating secondary pollution.

● Extremely Low Operating Costs: Energy consumption is primarily from the fan and low-power water pump; no chemical additives are required, and daily maintenance is simple, making it one of the lowest-cost deodorization technologies.

● Green and Environmentally Friendly: The process is natural and produces no other waste, making it an environmentally friendly biotechnology.

● Strong Resistance to Shock Loads: The mature microbial community has a certain buffering and adaptability to concentration fluctuations.

● All-PP Material with Corrosion Resistance: The main body of the equipment requires no anti-corrosion maintenance for its entire lifespan, solving the maintenance problems of long-term operation.

● Low Energy Consumption and Sustainability: In line with the concepts of energy conservation, emission reduction, and sustainable development.

▍ Scope of application

Biological filters are particularly suitable for treating large volumes of low-concentration odorous gases and biodegradable volatile organic compounds (VOCs).

Typical application industries:

● Wastewater treatment plants: Treating odorous gases such as H₂S, NH₃, and mercaptans generated in screen rooms, influent pump stations, aerated grit chambers, primary sedimentation tanks, sludge thickening tanks, and dewatering workshops.

● Waste treatment facilities: Treating complex odorous gases generated in waste transfer stations, landfills, and composting plants.

● Food processing industry: Treating fishy, sour, and fermentation-related waste gases generated in slaughterhouses, seafood processing plants, feed mills, and food brewing plants.

● Chemical and pharmaceutical industries: Treating low-concentration, biodegradable organic waste gases (such as alcohols, aldehydes, ketones, and esters).

● Livestock and poultry farming: Treating odorous gases such as ammonia and hydrogen sulfide generated in livestock farms and livestock manure treatment plants.

● Printing and coating industry: Pretreatment of low-concentration, water-soluble organic waste gas.

▍ Important Notes:

● Not suitable for treating high concentrations of pollutants that are difficult to biodegrade (such as halogenated hydrocarbons) or are highly toxic.

● The exhaust gas temperature typically needs to be controlled between 5-60℃.

● Pretreatment of the exhaust gas is required, such as dust removal, dehumidification (if necessary), and cooling, to prevent dust from clogging the filter media pores and to prevent high temperature and humidity from affecting microbial activity.

● Microbial acclimatization requires a certain amount of time (start-up period), typically 2-8 weeks.