WASTEWATER TREATMENT SOLUTION FOR PIG FARMS BY NEW TECHNOLOGY

Pig farming is mainly distributed in the Red River Delta, the Highland, the Northern Mountainous area (25%); the Central North and Central Coastal Area (19%); Mekong Delta (13%); the Southeast and Highland (11% and 7%).

1.1 Household scale (or traditional farming):

• ~ 4 million households with the scale of 10-100 pigs in a small area, which is often in combination with fish farrming or crop cultivation
• Pig farming wastes are being used to feed fish or manure plantation.

1.2 Farm scale (industrial farming):

• ~ 5.000 farms with scale more than 100 pigs in a large area
• Farms are divided into sow farms (together with newborn pigs) and market hog farm. Some farms mix sow and market hogs

There are two kinds of cage system designed by pig farms including enclosed cage and open cage. Enclosed cage system comprises of completely enclosed cage and partly enclosed cage.

2. Characteristics of wastewater from pig farms and conventional treatment technologies

• Water consumption: 15 to 60 l/pig/day.night (Survey results of pig farms with scale of more than 1000 pigs)
• Average amount of wastewater: 25 l/pig
• Manure amounts generated by market hogs is estimated to be 2.7 kg/pig/day, which is not separated but discharged with cleaning water into biogas tank.
• Most hog farms do not carry out separate collection and treatment of solid wastes.
• Pig manure, residual food, urine and cleaning water are treated by biogas tanks.
• Concentration of pollutants in wastewater is very high: COD ~ 6000mg/l, Amonia ~1200mg/l

Characteristics of pig farming wastewater vary significantly depending on farming methods and facility management (such as whether solid waste and wastewater should be separated or not), specific conditions of each province. These conditions have significant impacts on treatment scale, and result in difficult and expensive maintenance of treatment system.

3. New technology to treat wastewater from pig farms

Currently, there are many livestock wastewater treatment technologies applied in Vietnam including manure composting, biogas technology, biological agents, bio-ponds, etc. The most optimum livestock waste treatment model is biogas system which controls odour, reduces pollutant content contained in wastewater, and utilize biogas for fuel.

Although some of farms apply some mixed methods for wastewater & effluents treatment, but still fail to meet the discharge standard including those generated by the farms with more complete wastewater treatment system (utilizing aerobic method in wastewater treatment system). Moreover, biological gas collected from biogas tunnels are not utilized completely. Some farms emit biogas to the environment; while other only utilize it for cooking and lighting rather than running electricity generators.

NGO’S NEW TECHNOLOGY TO TREAT WASTEWATER FROM PIG FARMS WITHOUT BIOGAS TANK, SAVING FOOTPRINT

Based on activated sludge methodology and our experiences from projects implemented in the past, we found that the speed of manure separation from wastewater will impact on the efficiency of bio treatment in later stage.

Our treatment process:

Key steps	Optional steps
Wastewater -> Hydraulic screen & Balancing tank -> De-silting & innital VF clarifier -> Bio treatment with micro aeration tube control -> Integrated VF clarifer	-> Ecological Pond -> Sludge storage tank

Water quality after key above steps can meet A standard (QCVN 40:2016/BTNMT). However, to increase the stability of the whole system and consistency of water quality after treatment, as well as reuse water, Ecological pond is recommended to include to make treatment process completed.

Total volume for key treatment steps is equivalent to 9-10 days HRT (V = 9 to 10 times of Q-daily discharge capacity), meaning that the key steps only take up as much volume as one biogas tank does in conventional process, still the water quality meet A standard as per QCVN 40:2016/BTNMT. Moreover, this process also optimize the usage of manure & sludge as fertilizer for plants, without generating CH4 gas.

Why NGO’s process can save that much space? Because we use airlift technology to create large circulation, diminish pollutant loading on activated sludge by increasing reflux ratio from 10 to 100 times higher than traditional process. In addition micro aeration tube control with pore size of aeration equal to 1mm diameter that help to elimiate dead zones and lengthen HRT.

Depend on the size of pig farm, normally for the farm of more than 1000 pigs, Ammonia-Nitrogen Blow-off Tower will be added in the process in order to collect ammonia gas and reuse as fuel.

 

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