Process control of circulating water solid particles (II) Regulating TSS through reasonable feeding!

Circulating water solid particles process control regulation model
In a recirculating aquaculture system, the solid particle process control model is a tool used to optimize the control of suspended solid particles (TSS). By building a model, the generation, removal and regulation of solid particles can be analyzed and optimized to ensure stable water quality and efficient operation of the system. The following are the detailed steps and methods for building and managing the model.

(1). Model Objectives     

Solid particle concentration TSS: 10mg/L

Optimize removal efficiency: Optimize the removal efficiency of solid particles by adjusting the operating parameters of the filtration equipment. The removal efficiency formula is:

ETSS=

ETSS: Removal efficiency (%)

TSSin: Influent TSS concentration (mg/L): Install TSS sensor at the water inlet of microfiltration machine to obtain value

TSSout: Outlet TSS concentration (mg/L): Install TSS sensor at the water inlet of aquaculture pond to obtain value

Reduce operating costs: Reduce energy consumption and equipment maintenance costs by optimizing management measures.

In recirculating aquaculture system, the concentration of suspended solid particles (TSS) is closely related to system energy consumption. By optimizing TSS control, energy consumption can be effectively reduced and system operation efficiency can be improved.

(2). Control Methods---Reasonable Feeding

     When the solid suspended particulate matter index exceeds 10mg/L through TSS monitoring, it is necessary to follow the following steps to regulate.

1. Accurate feeding: Calculate the feeding amount to avoid excessive feeding and excessive residual feed.

2. Adjust the feeding strategy: According to the type, size, growth stage and feeding conditions of the cultured organisms, formulate a scientific feeding plan and adopt appropriate feeding methods, such as feeding in small amounts and multiple times, to reduce the residual feed from entering the water body to form solid particles.

It is recommended to use an automatic feeding machine to feed, which can not only achieve accurate feeding, but also feed in small and frequent meals. Our company has launched an intelligent feeding machine for recirculating aquaculture. The weight error is less than 3% through weighing sensors. The feeding is automatic throughout the process without manual intervention. Not only does it replace manual labor, but it can also easily achieve a feeding strategy of small and frequent meals.

3. Actual combat case

The circulating water culture of white shrimp, 1000 cubic meters of water, the culture density is 15kg/cubic meter, and the feeding rate is 3%. The suspended particle removal rate of the circulating water system is 60%, and it is circulated every 2 hours, and a feeding strategy of 4 meals a day is adopted. Monitoring found that the TSS peak value exceeded 20.25mg/L.

After finding that TSS exceeds the standard, the feeding frequency can be increased while the total daily feeding amount remains unchanged, and the feeding strategy of changing 4 meals a day to 12 meals a day can be changed.

    Calculate the TSS concentration of 4 meals a day:

    Water volume: 1000 cubic meters

Farming density: 15 kg/m³

Feeding rate: 3%

Suspended particle removal rate of circulating water system: 80%

Circulation frequency: once every 2 hours, 12 times a day

Feeding strategy: 4 meals a day

Step 1: Calculate the total biomass

First, calculate the total biomass in the aquaculture system.

Total biomass = water volume × aquaculture density = 1000 m3 × 15 kg/m3 = 15000 kg/day

Step 2: Calculate the daily feeding amount

According to the feeding rate, calculate the daily feeding amount.

Daily feeding amount = total biomass × feeding rate = 15000 kg × 3% = 450 kg/day Daily feeding amount = total biomass × feeding rate = 15000kg × 3% = 450kg/day

Since there are 4 meals a day, the feeding amount for each meal is:

Feeding amount per meal = 450 kg/4 = 112.5 kg/meal

Step 3: Calculate the increase in TSS for each cycle

Assume that after feeding, the feed will be converted into suspended particles.

After each feeding, the increase in TSS is:

TSS increase = feeding amount per meal = 112.5 kg

Step 4: Calculate TSS removal for each cycle

The circulating water system removes 80% of suspended particles in each cycle. Therefore, the TSS removal after each cycle is:

TSS removal = current TSS × 80%

Step 5: Simulate TSS changes within 24 hours

We need to simulate TSS changes in a cycle every 2 hours within 24 hours. There are 12 cycles a day, and a total of 12 cycles in 24 hours.

Initialize TSS to 0 kg.

Steps for each cycle:

Feed (once every 6 hours, i.e. once every 3 cycles)

Remove 80% of TSS

 Calculate TSS concentration of 12 meals per day

Water volume: 1000 cubic meters

Farming density: 15 kg/m³

Feeding rate: 3%

Removal rate of suspended particles in circulating water system: 80%

Circulation frequency: once every 2 hours, 12 times a day

Feeding strategy: 12 meals a day

Step 1: Calculate total biomass

First, calculate the total biomass in the aquaculture system.

Total biomass = water volume × farming density = 1000 m3 × 15 kg/m3 = 15000 kg

Step 2: Calculate daily feeding amount

Calculate the daily feeding amount based on the feeding rate.

Daily feeding amount = total biomass × feeding rate = 15000 kg × 3% = 450 kg/day

Since there are 12 meals a day, the feeding amount for each meal is:

Feeding amount per meal = 450 kg/12 = 37.5 kg/meal

Step 3: Calculate the increase in TSS for each cycle

Assume that after feeding, the feed will be converted into suspended particles. After each feeding, the increase in TSS is:

TSS increase = feeding amount per meal = 37.5 kg

Step 4: Calculate the TSS removal for each cycle

The circulating water system removes 80% of suspended particles in each cycle. Therefore, the TSS removal after each cycle is:

TSS removal = current TSS × 80%

Step 5: Simulate TSS changes within 24 hours

We need to simulate the TSS changes in 48 hours, with a cycle every 2 hours. 12 cycles per day, 12 cycles in total for 24 hours.

Initialize TSS to 0 kg.

Steps of each cycle:

Feeding (once every 2 hours, i.e. once per cycle)

Remove 80% of TSS

From the above analysis, we can see that:

4 meals a day: The amount of suspended particles produced increases rapidly after feeding, and then gradually decreases. The peak value is high (22.68 kg) and the fluctuation is large.

12 meals a day: The concentration of suspended particles is stable at 9.37mg/L

Conclusion: Through the feeding mode of small meals and frequent meals, TSS can be reduced and the energy consumption of equipment can be reduced.

The feeding mode of 12 meals a day can effectively reduce the peak concentration of suspended particles, reduce water quality fluctuations, and reduce the load and energy consumption of filtration equipment.

The feeding mode of 4 meals a day will cause large fluctuations in the concentration of suspended particles and increase the energy consumption of filtration equipment and water pumps.