People now choose to live in urban areas and huge groups as the population grows. In order to address the treatment challenges on a broader scale, India has begun to develop decentralized sewage treatment plants. These systems are fantastic because they provide an alternative to a centralized sewage treatment facility. However, the problem arises when the plant is not operated correctly.
COMMON ISSUES FACED BY SEWAGE TREATMENT PLANTS
1. DOWNSTREAM EQUIPMENT FAILURE
In the initial step of the sewage treatment process, downstream equipment is used. The screening process is in charge of removing non-biodegradable floating solids from the water. Solids such as paper, tin, plastic, rags, wood, and containers are frequently encountered in wastewater treatment plants.
As a result, you must remove these wastes from the water to prevent downstream equipment from harm such as pipe blockage, excessive wear and tear, and the accumulation of unwanted items that obstruct the wastewater treatment process. It is possible to clean the screening equipment both mechanically and manually. Many screening products can improve the stability of your downstream equipment significantly.
2. TREATED EFFLUENT NOT MEETING THE TOTAL PHOSPHOROUS TARGET
In terms of total phosphorus, India's sewage treatment plant is used for the following:
- Chemicals will be used as little as possible.
- To cut down on operating costs
- To obtain the TP license limits
There is a certain chemical dosage that must be followed in order to remove or level the total phosphorous target. You can use the fast analysis below to analyze the treatment facility and determine which chemical will work best.
- Pre-precipitation: To remove the phosphorous from the settling tank, a chemical dosing method is used. Pre-precipitation occurs when this occurs before the biological process, at the primary stage. You can use an online phosphate meter between the primary settling and aeration tanks to find out how much phosphate is in your water. You will be able to obtain feedback control as a result of this.
- Post-precipitation: It is when chemical dosing is used after the biological process to remove Phosphorous from final clarifiers or effluent filters. Between the final clarifier and the aeration tank with feedback control, the measurement should be obtained.
- Simultaneous dosage: When chemical dosing occurs both before and after the biological process, it is referred to as simultaneous dosing. This aids in achieving low phosphorus effluent limits.
3. ODOR PROBLEMS RELATED TO THE SEWAGE TREATMENT PLANT
The presence of hydrogen sulphide causes odor, but it can also comprise mercaptans and organic acids, which encourage the growth of Sulphur-reducing bacteria. Hydrogen sulphide (H2S), a colorless gas with a nasty, pungent stench similar to rotten eggs, is produced by the bacteria. Because hydrogen sulphide gas is extremely corrosive, it must be evacuated and treated to avoid downstream device failure.
Identifying the root of any odor problem is the first step in resolving it. Raw wastewater exposed to air at the influent pump station and main clarifier stage could be the source of odors. Regrettably, the odors could be originating from almost any other step in the treatment process. Because the source of odors could be a variety of things, or a mix of them, it's preferable to identify the source of odors with the help of a professional consultant, who can recommend an odor control technology that's best suited to your plant's needs.
4. TARGETS FOR BIOCHEMICAL OXYGEN DEMAND (BOD) IN TREATED EFFLUENT ARE NOT MET
The biochemical oxygen demand (BOD) is a measurement of how much oxygen is needed to degrade organic materials in water biologically. In general, when BOD levels are high, dissolved oxygen (DO) levels decrease. This is because the bacteria have a high need for oxygen, which they get from the oxygen dissolved in the water. If there is little organic waste in the water, there will be fewer bacteria to digest it, resulting in a lower BOD and a greater DO level.
There are a variety of reasons for high effluent BOD levels in the treated effluent, some of which are listed below. Getting these settings right will go a long way toward lowering your BOD levels.
- Organic overloading causes incomplete wastewater treatment.
- The oxygen content is low.
- Detention time for hydraulics is short.
- Short circuiting on the physical level
- High levels of algae or Sulphur bacteria
- Sludge buildup and effluent loss of ancient sludge
5. THE TOTAL NITROGEN (TN) TARGETS FOR TREATED EFFLUENT ARE NOT BEING MET
To figure out where your problem is, test for ammonia, nitrite, and nitrate. This will tell you where you need to focus your efforts in order to get your plant to cooperate. Most of the time, you'll find that your plant has high levels of either ammonia or nitrate, both of which contribute to high TN levels.
The biological mechanism of removing ammonia is entirely aerobic. If your plant has a high ammonia level, make sure it contains the following:
- Nitrification occurs exclusively in aerobic environments with dissolved oxygen levels greater than 1.0 mg/L.
- Nitrification necessitates a lengthy retention period.
- A low ratio of food to microorganisms (F:M)
- The average cell residence duration is rather long (measured as MCRT or Sludge Age)
- pH buffering that is adequate (alkalinity)
HIGH NITRATE CONCENTRATION
Bacteria that dwell in a low-oxygen environment undertake the biological reduction of nitrate to nitrogen gas. Biochemical oxygen demand (BOD) – soluble BOD – is required for bacteria to flourish. Before it can be used, particulate BOD must be broken down into solution.
It's usually for one of the following reasons why you have high treated effluent nitrate levels. Getting these settings right will go a long way toward lowering your nitrate levels.
- A sufficient carbon source. Denitrifying bacteria require a large amount of soluble BOD (up to five times the amount of nitrate being denitrified), and many facilities struggle to keep a steady supply of easily digestible BOD on hand.
- It is impossible to denitrify wastewater without first nitrifying it. If the nitrification process isn't working, there won't be any nitrate to denitrify.
- Make sure the anoxic tank's DO is 0.0mg/l. If the reading is greater than 0mg/l, the Mixed Liquor Return Rate (MLR) may need to be adjusted, but this flow rate is normally set at 300 percent of the daily incoming flow as a rule of thumb.