The City of Hua Hin operates two Wastewater Treating Plants. The first one is located directly in the city (ถนน แนบเคหาสน, 11 Naebkehardt Rd.), whereas the second one is located approx. 6.9 km southern (ซอย เพชรเกษม ๘๙ ตำบล หนองแก, 89 Phet Kasem Rd., Tambon Nong Kae).

Both use a different approach in cleaning the water. The first one uses the RBC (Rotating Biological Contactor) method, wheras the second uses the OD (Oxidation Ditch) approach. Both methods are desribed in detail below.

BOD and SS are important water quality parameters. BOD (Biochemical Oxygen Demand) measures the amount of dissolved oxygen needed by microorganisms to decompose organic matter in water, while SS (Suspended Solids) refers to the non-dissolved particles present in the water sample. Both indicate the level of pollution and can impact water quality and aquatic life.

BOD (Biochemical Oxygen Demand)

What it measures:
The amount of oxygen required by bacteria and other microorganisms to decompose organic matter in water at a temperature of 20°C in a given time, usually 20 days = BOD20. As this is long, the BOD5 is introduced, which aproaches 68%...70% of the BOD20 - in just 5 days. This has become a de facto standard, worldwide.

Importance:
High BOD indicates a high level of organic pollution, which can deplete dissolved oxygen levels in the water, harming aquatic life.

Factors affecting BOD:
The type and amount of organic matter, the temperature of the water, and the presence of microorganisms.

Typical values:
Purdue University indicates that for a BOD value greater than 12 mg/l, the Biological Oxygen Demand Index (IBOD) is 0. Hach Thailand notes that BOD is an essential measurement for limiting organic pollution in water.

SS (Suspended Solids)

What it measures:
The total weight of solid material that is suspended in the water.

Importance:
High levels of SS can cause turbidity, interfere with drinking water treatment, and potentially carry pollutants.

Sources of SS:
Erosion of land surfaces, urban runoff, and industrial discharge.

Typical values:
Purdue University indicates that for a Total Suspended Solids (TSS) value greater than 250 mg/l, the total Suspended Solids Index (ITSS) is 0. Butler Manufacturing Services notes that normal European discharge standards for SS are 35 mg/l.

Relationship between BOD and SS:
High SS can contribute to high BOD. When SS are high, the amount of organic matter they carry can increase BOD. Therefore reducing SS can lead to lower BOD. Removing or treating SS can help reduce the amount of organic matter in the water and thus lower BOD.

Summary

Both BOD and SS are important water quality parameters that indicate the presence of organic matter and solid particles in the water, respectively. High levels of both can indicate water pollution and negatively impact aquatic life and water treatment processes.

Rotating Biological Contactor, as seen in 11 Naebkehardt Rd., Hua Hin


A rotating biological contactor (RBC) is a wastewater treatment method that uses rotating discs to support microbial growth and remove pollutants from wastewater. The discs, partially submerged in a tank, are rotated, exposing the microbes to both the wastewater and the air, allowing them to degrade organic matter. This process is a secondary treatment step, following primary treatment, and is known for its simplicity, reliability, and low energy consumption.

How it works:

1. Attached Growth:
Microorganisms attach to the surface of the rotating discs, forming a biofilm.
2. Alternating Exposure:
As the discs rotate, the biofilm is alternately exposed to the wastewater and the atmosphere.
3. Aerobic Degradation:
During the submerged phase, microbes absorb organic pollutants from the wastewater. During the aerial phase, they take up oxygen from the air, allowing for the aerobic degradation of the pollutants.
4. Sloughing Off:
As the biofilm grows, excess biomass detaches from the discs and is carried through the system for removal in a clarifier.

Advantages:
• Simple Design - RBCs are relatively simple to design and operate.
• High Reliability - they are known for their reliability and long lifespan.
• Low Energy Consumption - they require less energy than other treatment processes.
• High Treatment Efficiency - RBCs can effectively remove organic matter from wastewater.

Disadvantages:
• In cold climates, RBC units may require covers to avoid freezing. Seems not an issue here.
• Shaft bearings and mechanical drive units require periodic maintenance.

The cleaned water is finally pumped to the Hua Hin Golf Club to let it seep into the ground, as the direct re-use somehow is against the believe of Thais.

An oxidation ditch (OD) is a type of wastewater treatment system that utilizes activated sludge to remove contaminants from sewage or industrial wastewater. The process involves a continuous flow of wastewater entering a large circular or rectangular ditch, where it is mixed with oxygen and microorganisms that break down organic matter. The microorganisms consume the organic material in the wastewater, reducing its pollutant content and improving its quality before it is discharged back into the environment. The oxidation ditch works by maintaining a controlled environment where the microorganisms can thrive and efficiently break down the organic matter in the wastewater. The ditch is designed to provide sufficient oxygen for the microorganisms to carry out the oxidation process, which converts organic pollutants into carbon dioxide, water, and other harmless byproducts. By controlling the flow rate, aeration, and mixing of the wastewater within the ditch, the process is always held at an optimal operating point to ensure that the effluent meets regulatory standards for discharge.

How it works:

1. Wastewater Input:
Raw wastewater, after preliminary treatment like screening, or removal of any anorganic substances, flows directly into the oxidation ditch, bypassing primary settling.
2. Aeration and Circulation:
Rotors or brushes (aerators) move the mixed liquor (wastewater and activated sludge) around the basin, providing circulation and oxygen.
3. Biological Treatment:
Microorganisms in the activated sludge consume the organic matter (BOD) and nutrients in the wastewater.
4. Nitrification and Denitrification:
Oxidation ditches can be designed for nitrification (converting ammonia to nitrate) and denitrification (converting nitrate to nitrogen gas) to remove nitrogen.
5. Sludge Separation:
The mixed liquor is then transferred to clarifiers where solids settle out and are removed as sludge, while the treated effluent is discharged.
6. Sludge Return:
A portion of the settled sludge (activated sludge) is returned to the oxidation ditch to maintain the population of microorganisms needed for treatment.
7. Effluent Disinfection:
The treated effluent may undergo further treatment, such as disinfection, before discharge.

And yes, the equipment originates from Sweden and the Netherlands. It proved to be a reliable coworker.

We would like to thank ผอ. มาดี รักษา, ผู้อำนวยการกองช่างสุขาภิบาล เทศบาลนครหัวหิน and น้อง วรรณ and น้อง หนุ่ม for realising an extraordinary guided tour.

ขอขอบพระคุณทุกท่าน


The tour was so very inspiring, that we invented the Madimod (coming soon). This is a complete Testbench for Water-Quality-Enthusiasts, based on our often copied Arduino / Genuino Mod series. This Testbench consists of four Mods, dedicated to measure and/or log the following parameters :

• pH Value [0...14] or Electronic Conductivity in mS/cm
• Temperature in °C
• Dissolved Oxygen, Range 0 ... 20 mg/l
• TDS Total Dissolved Solids in mg/l

• The King’s Royally Initiated Laem Phak Bia Environmental Research and Development Project
• The LERD Project, available in English
• The LERD Project @ Facebook
• The LERD Project @ YouTube

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