Features
2 Anaerobic Treatment of Beverage Plant Effluent
Haruo Kurisu
Environmental System Div.
Sumitomo Heavy Industryies, Ltd .

Introduction

Nowadays, soft drink is called the New Age drink, and product development is conducted frequently. In concurrence with demands on the variety of such commodity, production processes, such as extraction, blending, heating, sterilization, and container filling, are also diversely improved. However, since the effluent from each process mainly consists of an element based on organic matter-carbohydrates, biotreatability method is considered a suitable means of processing such by-products.In this paper, the features of beverage plant effluent and the application of an anaerobic biotreatability method are described.

1. Features of beverage plant effluent

The concentration of polluted effluent is variously produced by the used materials and processes. The relatively summarized data from both anaerobic methods, UASB and EGSB, is shown in Table-1. In order to perform general effluent treatment efficiently, water from every process (every facility) is collected and high concentration effluent is treated using the anaerobic method. Depending on the desired value of effluent during the final treatment, in many cases, low concentration effluent is disposed by aerobic biotreatability method together with the effluent yielded by anaerobic treatment. The example of CODcr of raw water for anaerobic treatment classified as high concentration effluent is shown in Fig. 1.

Table-1 Effluent Concentration Rank
Table-1 Effluent Concentration Rank

Fig.1 Influent CODcr
Fig.1  Influent CODcr

2. Application of the anaerobic method

The UASB (Upflow Anaerobic Sludge Blanket) method and the EGSB (Expanded Granule Sludge Bed) method, which is a high load type system, are the present mainstreams in the anaerobic form of wastewater treatment. EGSB is applied to comparatively dilute effluent (BOD 1000 mg/l), as well. Some waste effluents need pretreatment, such as removal of excessive SS, n-Hex extract, bactericidal properties, neutralization, etc. on the application for beverage plant effluent. In this paper, wastewater with peroxide, as a practical example of bactericidal properties, is first described. Secondly, the anaerobic method is described.

2.1 Pretreatment of wastewater with peroxide

The peroxide used for container sterilization in Table-1 is a mixture of hydrogen peroxide and acetyl hydroperoxide, and has bactericidal properties. After alkaline neutralization, the method using activated carbon and catalytic agent is easier to perform as compared with the utilization of redox reaction by thiosulfuric soda. If the treated water has high concentration of peroxide, the anaerobic method is applicable.

Acetyl hydroperoxide and hydrogen peroxide are reduced when in contact with activated carbon. They emit oxygen and become transformed to acetic acid or water. An example of an equipment using activated carbon is shown in Fig. 2. In order not to mix treated water with fluidized activated carbon due to the generation of oxygen gas, the equipment is devised. After generated oxygen gas is separated, it is emitted from the upper section of the tank. The devised equipment can reduce hundreds of mg/l - thousands of mg/l of peroxide to minute mg/l in quantity of peroxide.

Fig.2 Reducing equipment of peroxide waste water
Fig.2 Reducing equipment of peroxide waste water

2.2 Anaerobic treatment flow

Both UASB and EGSB methods are composed of two processors (an acidification tank and a reactor tank), which are shown in Fig. 3. The acidification tank has ph and temperature regulator, including organic oxidant of organic contaminant.

Phase III separator, called settler, is installed in the upper section of the reactor tank. In the EGSB, a design value of gas and liquid ascending flow in the tank is designed largely. In connection with it, the settler in the upper section of the tank is suitable. Both of the acidification and reactor tanks are tightly sealed to completely block the air and to avoid leaks.

The EGSB results in a greater bacterial fluidization as compared with the UASB. There are many treatments per unit volume. Standard CODcr volume load of the EGSB is 20?30 kg-CODcr/m3・d while the UASB is 10 - 15 kg-CODcr/m3・d. Compact units for the EGSB and the UASB are developed.

Fig.3 UASB(BIOTHANE) and EGSB(BIOBED) Process
Fig.3 UASB(BIOTHANE) and EGSB(BIOBED) Process

2.3 Operation management and outcome of the anaerobic treatment

When facilities deal with oil and influent control of SS in the pretreatment, the operation management point of the anaerobic method can be said to be an input load and inflow water pH into the reactor tank. From a fail safe point of view, the measurement of pH is required for the installation of some equipment. (example of installation location: an acid product tank, a reactor tank inflow piping or circulating water piping). In addition, the measurement of the amount of gas generation, CODcr, in the treated water and VFA (organic acid) concentration are performed as management. However, the operation situation is mainly checked by VFA because CODcr may include the influence of the ingredient’s color. Input load of VFA needs to be adjusted not to exceed a maximum of 200 mg/l. The result of treated water of an actual facility is shown in Fig. 4. VFA clears the management value sufficiently in the mean value. If standard deviation is included, some facilities exceed cautious concentration. In such scenario, monitoring is conducted, such as an increase in analysis frequency. Furthermore, when feasible, load adjustment is done even for short term. In addition to daily management, at least a monthly bacterial load (height) retained in the reactor tank needs to be measured and any change is monitored.

Fig.4 Results of Effluent CODcr and VFA
Fig.4 Results of Effluent CODcr and VFA

Finally

The anaerobic treatment salvages energy in the form of methane gas. Other possible ways to recover energy is through production of electricity (co-generation of exhaust heat recovery) by micro-gas turbine and fuel battery. However, to date, when anaerobic treatment is employed on the disposal of beverage plant effluent, in most cases, energy is recovered in stream because of the problem in the change and scale of gas generation. On the other hand, residues from coffee and tea, depending on thefactory, are generated. They are considered biomass resources. When treated anaerobically, the method differs from the ones introduced in this paper. If these lees are treated anaerobically, the amount of BIOS will increase, and it is thought that electric power regained progresses together with the development of methane gas storage equipment.


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