Application of sewage treatment technology


Application of water treatment technology

POLYCO GROUP’S introduction

Sewage treatment system for breweries

With a consumption of 3.8 billion liters in 2015, Vietnam is one of the largest beer markets in Asia. According to brewing industry, in 2015, beer consumption in Viet Nam is 41 liters per person, just behind Korea and Japan in Asia. Beer industry with annual growth rate in the past 10 years is 6.4% and the last 5 years is 5.7% and accounted for 94% of the consumption of alcohol, so in recent years there are more and more breweries invested. In addition, the state policy encourages brewing industry as a strong economic sector to increase state budget revenues. However, in addition to the growth of brewing industry, sewage is one of the problems that need solving.

Sewage from breweries

Beer contains mostly water (> 90%), ethanol (3 - 6%), CO2 and other solvents. The brewing industry is one of the largest users of water, the average water use of Sabeco and Habeco is about 4.6 to 6.0 liters per liter of beer. Brewing is therefore one of the industries that requires a lot of water, so it emits a very large amount of sewage. Sewage from breweries usually includes the following types:

    1. Cooling water, condensate. This type of water is not polluted so it can be pre-treated and re-used;

   2. Water using for sanitary equipment such as washing pot cooking, tank, floor of manufacturer. This sewage contains a lot of organic matter which needs to be treated to clean the environment and re-use;

   3. Sanitary water and fermentation equipment, pipeline containers, fermented floors. This type of sewage contains many yeast carcasses, the yeast is easy to decay causing serious pollution. This type of sewage requires special treatment to reduce the risk of contamination;

  4. Sanitary water using for washing beer bottle s. This type causes seriously polluted, this includes not only organic substances but also many color compounds from labels and metal.

 

            

Picture 1. Diagram of production technology and emissions breweries

Suitable technology

 

Sewage from breweries is highly organic pollution which decomposes very quickly so sewage is black and it causes serious pollution plus additives and chemical process of production such as CaSO4, H3PO4 , NaOH, Na2CO3 etc If not being treated, these substances will cause seriously environmental pollution when the sewage is discharged directly to the receiving source without being treated well.

Based on the above analysis, sewage treatment in beer production to reuse is the most effective solution. Sewage from brewery’s operations has high nutrient content and traditional treatment methods by introducing sewage into urban or industrial sewage treatment plants, both wasteful and pressurized to the downstream source. In addition, sewage treatment of urban sewage treatment plants or industrial zones greatly increases the cost of breweries.

Because of the potential value of sewage from brewery rich in carbon and nutrients (N / P), the choice of optimal technology can save costs, can use renewable energy and reuse to reduce cost is an urgent need. 

Table 1. Characteristics of sewage from brewery 

Parameter

Unit

sewage from brewery

 

Flow

-

-

2-8 hL sewage/hL beer

COD

mg/L

2000–6000

0.5-3 kg COD/hL beer

BOD

mg/L

1200–3600

0.2 – 2kg BOD/hL beer

TSS

mg/L

200–1000

0.1-0.5 kg TSS/hL beer

pH

 

4.5–12

 

Nito-N

mg/L

25–80

 

Photpho-P

mg/L

10–50

 

Heavy metal

mg/L

Very low

 

 

 

There are many technologies to treat sewage from breweries. However, with the current conditions, current breweries such as Sabeco and Habeco choose anaerobic and aerobic treatment technologies. The use of this technology results in lower operating costs and stable discharge quality and high system safety.

With a high organic content, the BOD5 / COD> 0.5 ratio should be treated with anaerobic and aerobic combined bioreactors. Sewage treatment technologies commonly used are: UASB (Upflow Anaerobic Sludge Blanket), combined with SBR (Sequencing Batch Reactors).

Table 2. Comparison between anaerobic and aerobic systems

 

Anaerobic technology

Aerobic technology

Eliminate COD

65–90%

90–98%

Generate energy

High: CH4 is produced as biogas

Low: CO2 only

Low energy consumption

Low

High

Sludge

Low

High

Remove (N / P)

Low

High

Space requirements

Low

High

Operation

Simple

Complex

 

Technology Introduction 

UASB anaerobic treatment process (Upflow Anaerobic Sludge Blanket):

In UASB tank, sewage is evenly distributed on bottom of the tank and goes from the bottom to the suspended sediment, then through mud layer (microorganism), anaerobic in tank will mix absorbs organic matters. (BOD, COD etc) dissolve in sewage, and break down and convert them into biogas (about 70-80% of methane and 20-30% of carbon dioxide and other gases). Output biogas is collected for  Biogas steamer [Installed for wastewater treatment system of Sai Gon - Hanoi Brewery] 

 

Picture 2. UASB system and collecting biogas to supply steamer

Advantages of UASB technology:

COD removal efficiency up to 90%

Sewage treatment with very high levels of organic pollution

Very low energy consumption during operation.

Sequencing Batch Reactors (SBR):

As a reactor works in the form of activated sludge treatment, two periods of aeration and gasification take place in the same tank. SBR system is a system for  treating of biological sewage containing organic compounds and high nitrogen. Continuous operation system includes the following process:

Anoxic Fill Phase: Sewage at this stage is distributed throughout the tank with activated sludge at the bottom of the tank. Bioprocesses occurring simultaneously in this stage are anaerobic and aerobic. Sewage flowing into the tank to the level indicator, the sensor signal level signaling the valve closed again.   

Reaction: After finishing Anoxic Fill Phase, sewage is continuously aerated with stirring. In this stage, sewage is treated until sewage is treated to the permitted level. This process creates a biochemical reaction between activated sludge and activated sludge. The length of ventilation and aeration are dependent on the quality of sewage and the level of treatment required.  

Sedimentation process: Aeration process and stirring stop, activated sludge is settled to the bottom of the tank. Sedimentation occurs in a static environment, the hydraulic effect of the tank reaches 100%.

Water splash in: Inner water is collected in the disinfection tank through decanter.

Activated sludge collection / retention: The tank is ready for loading. Activated sludge is pumped into the slurry tank.

Cycle work cycles are installed through intelligent and flexible control software.