Pig farming wastewater treatment technology

Overview of the livestock industry

In 2020, the Department of Livestock Production targets production value growth of about 4%; Meat output of all kinds reached about 5.5 million tons, pork about 64-67%, poultry about 25-27%, grass-fed meat about 9-11%.

Egg production reached about 14.5 billion eggs and milk production reached about 1.2 million tons

The average livestock product/person is about 57 kg of meat of all kinds, about 130-135 eggs, about 13-15 kg of fresh milk.

The proportion of cattle and poultry slaughtered industrially is about 50% and 40%, respectively.

The proportion of processed livestock and poultry meat compared to the total annual meat production is about 20-25%, respectively.

Basic characteristics of pig farming wastewater

Pig farming wastewater is one of the very typical types of wastewater, capable of causing high environmental pollution with its content of organic matter, suspended residue, N, P and disease-causing organisms.

It must be treated before being released into the environment. Choosing a wastewater treatment process for a livestock facility depends greatly on the composition and properties of the wastewater, including:

Organic and inorganic substances

• In livestock wastewater, organic compounds account for 70 – 80% including cellulose, proteins, amino acids, fats, carbohydrates and their derivatives in feces and leftover food.
• Most organic substances are easily decomposed. Inorganic substances account for 20-30% including sand, soil, salt, urea, ammonium, chloride salt, SO2-.

Nitrogen and Phosphorus

• The ability of livestock and poultry to absorb N and P is very low, so when they eat food containing N and P, they will excrete it in feces and urine.
• Pig farming wastewater often contains very high N and P content.

Pathogenic microorganisms

• Livestock wastewater contains many types of bacteria, viruses and helminth larvae that cause disease.
• According to research by many authors (A. Kigirov, 1982; G. Rheiheinmer, 1985…), the foot-and-mouth disease virus in wastewater can survive from 100 – 120 days.
• Helminth eggs can develop to the infectious stage after 6-8 days and survive for 5-6 months.

Pig farming wastewater treatment technologies.

Treated by anaerobic method

Anaerobic treatment process with microorganisms growing in suspension

Anaerobic sludge treatment tank with bottom-up water flow (UASB)

Regarding structure: UASB tank is a treatment tank with a sludge layer at the bottom, with a system to separate and collect gas and water at the top.

When wastewater is distributed from the bottom up and passes through the sludge layer, the high density anaerobic microorganisms in the sludge will decompose the organic substances in the wastewater.

Inside the UASB tank there are barriers capable of separating sludge dragged along with the output water.

Characteristics: All three processes of decomposition – sludge sedimentation – air separation are installed in the same project. After stable operation in the UASB tank, a granular sludge is formed with very high microbial density, strong activity and sedimentation speed far exceeding that of suspended aerobic activated sludge.

Treatment with Biogas

Biogas tank: Biogas technology is based on the operating principle of anaerobic microorganisms.

In the absence of oxygen, microorganisms decompose organic matter into active energy and methane gas.

The mixture of CH4 (Methane), hydrogen sulfide (H¬2S), NOx, CO2… creates biogas.

Biogas tanks under the influence of high-speed microbial products, combined with the impact of anaerobic microorganisms, will ferment wastewater, reducing the content of pollutants in livestock wastewater.

Suitable for the load capacity of the livestock wastewater treatment system after Biogas, and at the same time produces Biogas gas to return to production.

BOD treatment efficiency is about 60%, so a second stage of treatment is needed to meet environmental standards.

Normally, about 1 cubic meter of incubation volume will produce 500L of Biogas.

Nam Viet constructs Biogas Pig farming wastewater treatment

Treated aerobically

Wastewater treatment using the artificial aerobic method is based on the need for oxygen to be provided for aerobic microorganisms in wastewater to operate and develop.

Aerobic microorganisms use organic substances, N and P sources along with some other trace elements as nutritional sources to build new cells and grow and increase biomass.

Besides, the process of intracellular respiration also takes place in parallel, releasing CO2 and water.

Both nutritional and respiratory processes of microorganisms require oxygen.

To meet the need for dissolved oxygen in water, people often use surface aeration systems by agitation or compressed air systems.

Treated by physicochemical methods

Use chemicals to sediment organic and inorganic substances in wastewater. A typical physicochemical treatment method is the coagulation – flocculation method, this method uses PAC and Polymer chemicals to coagulate and form flocs with a density heavier than water, from which, thanks to gravity, the These residue particles easily settle to the bottom of the treatment tank and are periodically collected and treated.

Treated by other methods

Oxidation ditch:

It is a ring-shaped ditch with aeration to create a flow in the ditch with enough speed to disturb the activated sludge.

The velocity in the ditch is usually designed to be greater than 3m/s to avoid sedimentation. Oxidation ditches can incorporate N treatment processes.

Intermittent tank (SBR):

Intermittent tank is a wastewater treatment system with activated sludge by filling and draining.

The process occurring in the SBR tank is similar to that in the continuously operating activated sludge tank, only all processes occur in the same tank and are performed sequentially according to the following steps: (1) filling, ( 2) reaction, (3) sedimentation, (4) sediment discharge, (5) condensation.

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Irrigated fields

Lead wastewater through the soil ditch system on irrigated fields, use pumps and distribution pipes to spray wastewater onto the ground.

Part of the water evaporates, the rest seeps into the soil to create moisture and provide nutrients for plants to grow.

This method is only used limitedly in places with small wastewater volumes, arid lands far from residential areas, high evaporation and soil always lacking moisture.

Irrigated fields must not grow vegetables and food crops because pathogenic bacteria and viruses in wastewater that have not been eliminated can cause harm to the health of people using these vegetables and foods.

Learn more about pig farming wastewater treatment technology here