Improved Ebb Method for Determining Void Volume

odor and inhibit the growth of Coliform bacteria in waste. The ingredients of the product include: Bacillus subtilis , Lactobacillus and Sacharomyces cereviciae . The effective density of microorganisms is 10 8 CFU/gram [68,69].

2.4. Analysis method

2.4.1. Method for determining COD

Determination of COD by Kalidichromate method according to ISO 6060: 1989 Standard Method. On Thermoreactor TR320, Merck- Germany.

- How to proceed:

Take 2 ml of sample wastewater into the COD tube. Add 1 ml of K 2 Cr 2 O 7 and 3 ml of Ag 2 SO 4 . Close the lid and record the sample symbol. Do the same with a blank sample. Put the COD tube in the sample stove to decompose the sample for 2 hours, then let it cool. Pour the solution into a conical flask and add 1 to 2 drops of ferroin indicator. The titration with Morth's salt is finished when the solution changes from ink blue to reddish brown.

- Calculate the result:

The COD content in water samples is calculated according to the following formula:

COD=[ C − CMoth ].C m .8000 (mg/L)

In there:

C is the volume of Morth's salt solution consumed for the blank sample standardization (ml) C Morth : the volume of Morth's salt solution consumed for the sample standardization (ml) C m : the equivalent concentration of Morth's salt solution

8000: conversion factor to mg O 2 /l

- Calculate COD treatment efficiency H = (C in – C out ) x 100/C in

- Calculate the retention time T = V/Q in

- Calculate COD load

L = C in (mg/L) x Q in (L/day)/(V x 1000)

In there:

T: Wastewater retention time (hours)

V: Volume of water in the reactor (liters) Q: Flow rate (liters/hour)

H: Processing efficiency (%)

C in : COD concentration (mg/L) C out : COD concentration (mg/L)

L: COD load (kg/m 3 .day)

2.4.2. Method for determining Ammonium

+ Determine NH 4 + by Phenat method (standard Method 1995), compare color on UV – 2450 machine (Shimazu, Japan).

+ Procedure: use a 25ml volumetric flask, containing: Volume of sample for analysis; 11.1% phenol solution; Natrinitroproside solution and oxidizing solution respectively 1ml; 0.5ml; 0.5ml and 1.25ml. Make up to the 25ml mark with distilled water. Leave in soft light for 45 minutes then compare the color at 630nm.

2.5. Manufacturing of improved EBB materials

2.5.1. Method for determining material porosity

2.5.1.1. Improved EBB method for determining void volume

Determine the mixing quantity of materials using the LP7516LCD New electronic scale, then dry mix the material mixture within 5 minutes, the purpose is to make the sand and cement adhere evenly to the surface of other materials. Measure the water using the Duran glass measuring cylinder and mix the material mixture again for 5 minutes. Observe with the naked eye and evaluate the adhesion of the material mixture before putting it into the mold. Determining the dry mix content is carried out twice, according to Table 2.2 .

Table 2. 2. Mixing content of dry materials.

Time

Material
Sand (%)	Keramzit (%)	Zeolite (%)	Coal (%)	Cement (%)
1	14	22	28	14	22
2	14	36	14	14	22

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After determining the binding content of materials and the water content, the research was conducted to test the improved EBB blocks to determine the effectiveness of the product and select the most superior mixing content. The monitoring and experiment were conducted under room temperature conditions, with natural oxygen. The experimental model for the improved EBB experiment is shown in Figure 2.2.

Input wastewater

Improved EBB solid blocks and tanks

Output

Metering pump

Figure 2. 2. Improved EBB experimental diagram.

The experiment was conducted on a test system with a total volume of 38 liters of wastewater tank. Of which, the useful volume is 19 liters. Domestic wastewater was collected from the sewer in Nghia Do ward, Cau Giay and poured into tank number 1. Here, domestic wastewater was transferred to tank number 3 by a metering pump (2). Wastewater in tank 3 automatically flows through the improved EBB material blocks. The COD and NH 4 + indicators were collected and analyzed daily with a flow range from 0.5 to 5 L/hour. The porous volume of the improved EBB material was calculated according to TCVN 7572-6:2006.

Step 1: Calculate the volumetric weight of the foam using the formula

ρ vx = m2 – m1 (kg/m 3 )

ρ vx : Foam volume mass of material ( g/m 3 ) m 1 : Mass of measuring tank (kg)

m 2 : Mass of measuring tank with material sample (kg) V: Volume of measuring tank (m 3 )

Step 2: The porosity of the material is calculated using the formula

V h = ( 1 - ρ vx ) . 100%

ρ v . 1000

ρ v : Bulk density of material (g/cm 3 )

ρ vx : Foam volume mass of material (kg/m 3 )

2.5.1.2. Improved EBB method for determining surface area

The study uses a scanning electron microscope (SEM) to create high-resolution images of a specimen surface by scanning the surface of the specimen with a narrow beam of electrons. The electron beam interacts with atoms near or at the specimen surface, generating signals (radiation) that contain information about the image of the specimen surface, elemental composition, and other properties such as electrical conductivity.

Normally the sample chamber of SEM is quite small, however in special SEM machines with large chambers, it is possible to measure samples with diameters up to 200 mm, height about 50 mm. The sample must be placed in a vacuum chamber to obtain high-resolution secondary electron images, chamber pressure about 10-5 ÷10-6 torr.

To obtain the most accurate sample information, sample preparation is very important. For non-conductive samples such as coal, kezamzit, zeolite, sand, cement to reduce the phenomenon of static electricity generated when exposed to X-rays, the sample surface needs to be coated with a thin layer of carbon (for normal samples) and the samples must be stabilized with stopping solutions, injected or immersed in aldehydes, osmium tetroxide, tannic acid, or thiocarbohydrazide, or immersed in a 1.5% glutaraldehyde solution containing 0.1 M cacodylic acid buffer (pH 7.3) and incubated overnight at 4 o C.

2.5.2. Method for determining water mixing content

The optimal water content is determined through experience in adding or removing water from each batch of improved EBB casting, in order to strictly control to avoid mixing too dry leading to an inadequate bond or mixing too much water leading to the cement and sand being washed out or locally clogged.

Table 2. 3. Additional water content for mixing

Content 1

Content 2	Content 3
100 ml	120 ml	150 ml

The study has proposed three water contents to be mixed with the materials to form the improved EBB product. The amount of water added to the mixture is presented in Table 2.3.

The mixed material mass of the improved EBB was selected for a void content of 64% corresponding to 300 g of dry material. The quality assessment results of the improved EBB pellets were qualitatively evaluated visually to select the most suitable water content while maintaining the stability of the improved EBB block.

2.5.3. Experimental fabrication of improved EBB

Through evaluation, material selection and analysis methods to create improved EBB materials, the study gives the material manufacturing formula as shown in Figure 2.3.

For example, the material mixture to produce improved EBB is 10 kg, so in which sand material accounts for 14% corresponding to 0.14 × 10 = 1.4 kg; kezamzit material accounts for 36%.

% respectively is 0.36 × 10 = 3.6 kg; cement material accounts for 14% respectively is 1.4 kg, similarly activated carbon 1.4 kg and zeolite material accounts for 0.22 × 10 = 2.2 kg. After determining the mixing content, the mixture is put into a Mini concrete mixer (MTBT 350 L, 2.2 kw/220v engine) for dry mixing, the dry mixing time takes 15 minutes, the sand and cement materials will adhere evenly to inert materials such as kezamzit gravel, zeolite and activated carbon. Next, clean water is added to the evenly mixed mixture, the amount of water added is calculated as 120 ml/300 g of material. After wet mixing for 5 minutes, the mixture is put into the mold with a pressing force of 10 to 20 kg/cm 3 . After 24 hours, the cement binds the materials, remove the mold and dry the improved EBB material.

Figure 2. 3. Experimental diagram of improved EBB production

2.6. Evaluation of characteristics of improved EBB materials.

2.6.1. Method of inoculating microorganisms into improved EBB materials

Air blower

Bacteria culture tank

After casting and drying the product for 24 hours, 50 improved EBB blocks were soaked and washed to remove dirt on the blocks and layers of cement dust that had not yet adhered to the improved EBB blocks.

Material

Figure 2.4. Inoculation of VSV into improved EBB

The time to inoculate microorganisms onto the EBB block from Sagi - Bio2 preparation is within 10 days. The improved EBB is put into the inoculation tank with a capacity of 50 liters. The qualitative results are shown in Figure 2.4 .

With a microbial density of 108 CFU /ml, the study added 50 ml of Sagi - Bio2 preparation to the microbial culture tank, along with an internal water mixing pump to enhance the adhesion and growth of microorganisms, supplement nutrients for microorganisms at a BOD:N:P ratio of 100:5:1 and monitor daily with the naked eye.

(i) Microbial culture process

The process of cultivating microorganisms includes two steps: cultivation and inoculation.

+ Breeding: creating the process of ensuring and maintaining the most favorable conditions for the operation and development of microorganisms.

+ Transplantation: the act of transferring microorganisms from their living environment to a more favorable environment for their growth.

- Quantification of microorganisms in experimental samples

- Method of quantifying bacteria by counting colonies on agar plates [70,71]

+ Sample dilution

 Pipette 1 ml of the modified EBB membrane into the first test tube containing 9 ml of sterile distilled water.

 Mix the solution thoroughly by sucking up and blowing down 3 times. The sample dilution is now 10-1

 Continue to draw 1 ml from the first test tube into the second test tube containing 9 ml of sterile distilled water.

 Mix well and the dilution is now 10-2

 Continue like this to get samples at dilutions of 10-3 , 10-4 , 10-5 ....

Depending on the estimated concentration of microorganisms in the sample, dilute the sample at different rates.

+ How to proceed

 Prepare agar plate medium: MPA, Czapek, Hansen medium is sterilized at 1 atm for 30 minutes, poured into sterile petri dishes, wait for the agar to solidify and dry the agar surface

 Write on the bottom of the petri dish containing the appropriate agar medium for each type of microorganism the following information:

 Dilution concentration

 Planting date

 Use a sterile pipette with a conical tip to drop 0.1 ml of appropriate dilutions (equivalent to 2 drops of solution) into each Peptide dish. Each dilution is repeated 3 times. Use a sterile spreader to spread the cell suspension evenly over the agar surface.

 Petri dishes were inoculated with cell suspension, sealed and placed upside down in a 37 o C incubator. After 24 hours, the number of colonies in each dish was counted.

- How to count

 Use a pencil to draw two perpendicular lines on the bottom of the petri dish and label each region I, II, III, IV.

 Count the number of colonies in each area and mark the counted colonies.

 The number of VSV cells in 1 ml of sample is calculated according to the following formula:

In there:

Number of cells

𝑚𝑙𝑚𝑢

𝑛

× 𝐷

𝑣

determine

n: Average number of colonies in a petri dish at a given dilution

v: Volume of sample to be cultured D: Dilution factor

2.6.2. Method for determining the effect of pH on microorganisms and COD treatment efficiency in improved EBB materials

To conduct the experiment, Sagi – Bio 2 preparation was inoculated into improved EBB. In this experiment, it is important to determine the number of microorganisms in improved EBB material at different pH levels.

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