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Design Approach for Sewage Treatment Plant: A Case Study on STP on a Private Textile company, Kamanaickenpalayam, Tamilnadu.

Abstract

The project details the study of domestic wastewater collected at a Private Clothing Company near Kamanaickenpalayam. This study focuses on the sewage generation in the above-mentioned location and modification of conventional sewage treatment plants by introducing OxyO technology. The total sewage generated was estimated at 150 KLD per day, considering the total population in the industry. The sample water collected from the conventional sewage treatment plant and characterization for the same has been done. The result has been provided (pH, Total suspended solids, Ammonia, Nitrate, COD & BOD).

The sewage treatment plant is quite necessary to receive the domestic and commercial waste and remove the material that harms the general public. The objective is to produce an environmentally safe fluid waste stream and solid waste (or treated sludge) suitable for disposal and reuse. This case study has done an up-gradation of the existing facility with OxyO technology and a comparative study of the conventional and OxyO technology.

Keywords: Attached growth process (AGP), Suspended growth process (SGP), Domestic wastewater, Nitrification, De-nitrification, biofilm

1. Introduction

 

As the environmental discharge standards are getting more stringent, the traditional continuous flow-based biological wastewater treatment process faces severe challenges. The moving bed biofilm reactor (MBBR) technology modifies the much popular attached growth process (AGP). Such a conversion of the continuous nature of the AGP-based treatment process helps introduce various process flexibilities and alternatives in-process controls and design to achieve the latest sewage discharge standards better.

Domestic wastewater could be considered a major source of water pollution due to its organic content and trace elements. It can be recognized by high concentrations of biochemical oxygen demand (BOD), COD, odour, colour and sludge. Biological wastewater treatment is an attractive technology to treat this type of wastewater due to the economic advantages in terms of operation. However, the treatment sites require a great deal of land and are costly to maintain, and the treatment process itself requires a lot of

 

Attention. Thus, alternatives have been introduced, such as biofilm treatment technology. This attached growth process utilizes a completely biological process and can be operated in just one tank. It works as a collection, aeration, equalization, and biological treatment in a single tank through a timed control sequence, making it environmentally friendly technology.

 

At Sahana, the STP set-up has been in operation for over a decade. The existing process requires fine-tuning to treat the domestic wastewater from the textile mill & its residential quarters with improved performance and lower sludge production.

Our process simplifies the operation, which has allowed us to provide solutions that traditional methods would not allow us. Our technique merely introduces a large consortium of active biomass from the media to the wastewater, where they are subject to effective utilization in a conducive environment to decontaminate. Accepted worldwide, the treatment is very successful consistently.

Many customers using biofilm technology feel the ease of operation with the void of sludge production. We can explain, “Since we realize the consequence of the suspended growth processing traditions, we have new opportunities.”

 

1.1   About OxyO technology

 

OxyO follows the principle of Universal Design, which means a process usable by as many people as possible. OxyO has many ideas; all created based on this principle. A well-executed Universal Design principle not only creates a process that is beneficial to end-users but is also a sensible performing model. Our solutions are unique and built to suit all customers. The size of the plant does not matter. Our principles of treatment remain unaltered in most cases. As these plants are small and, in some cases, mobile, it is a question of transporting treated wastewater for reusing or disposal to farms. The shape of all capacities remains the same but dimensions vary. Our biological treatment, irrespective of the size, is very well established, unlike conventional plants incapable of consistently performing. The smallest plant that can be designed and operated may be as low as 500 LPD.

Our designs are standardized for various capacities. On short notice, these DIY kits can be supplied to the end-users who need no specialized skills to start their biological process plants. The aim is to minimize the struggle of operating the biological treatment plants. We endeavour to forge the most efficient wastewater treatment with simple processes for the end-user. All our plants have operated without the need for any external help for initiating microbial activity.

All our plants past three years, starting from 5 KLD onwards in various locations, have performed with no human interference to produce quality treated wastewater either for reuse or disposal.

Since the inception of OxyO, some of the 15 wastewater treatment plants set up are 2.50 KLD to 300 KLD, all performing to the customers’ expectations. They are our referrals. The treated wastewater in some places is partially reused for gardening, irrigation and flushing in toilets.

Biofilm Technology – with biofilm, the disadvantages of activated sludge are negated. In fact, a reduction in the gradient of organics by introducing beyond one day’s collection facility offers some remarkable advantages. The ultimate objective is the same to apply massive active biomass for treatment. We have achieved it in the collection facility. This actually eliminates the need to design any further or separate operations.

 

 

Advantages of our Treatment Technology

 

  1. Can start the plant without seeding from outside
  2. No chemical consumption is incurred.
  3. The blower to the aeration tank shall be a dedicated air supply for biological treatment in the aeration
  4. Biological activity will never be sluggish even if there is no
  5. Design based on retaining biomass in the aeration tank for increased biological activity

– viable cell count, which will never be sluggish.

  1. The existing facility utilized with minimal
  2. Sludge production Odor is automatically controlled as a result of improved biological activity.
  3. Treated water after disinfection meets all statutory standards and is fit for
  4. The sludge generated is full. This slurry can be directly used for horticulture without further treatment.
  5. Reduced power consumption and lowered maintenance
  6. No requirement for manual
  7. Dependence on operator’s skill

 

1.2   CHALLENGE

 

  1. The existing treatment process of capacity 150 KLD at Sahana Clothing Company Private Limited

Activated sludge process – Very well established process, extensively used by most operators. With activated sludge, wastewaters are treated by suspended growth bacteria. Using this method equalization of waste and constant flow to the reactors, by definition, will take a long time to reach the desired results. This means any shortcoming in the design of the collection and reactor sizing can lead to under treatment. Other disadvantages resulting from change organic content, either a reduction or increase, define treatment quality apart from sizable sludge production.

The existing sewage treatment plant is designed to treat 150 KLD.

The treatment unit was designed based on the population in the textile mill & its residential quarters at the Sahana clothing company Pvt. ltd., the process involved in the existing sewage treatment plant is as follows,

1/ Raw sewage from bar screen chamber flows into collection tank by gravity having capacity 40 cum.

2/ The sewage from the collection tank shall be pumped using a 2 HP raw sewage pump to the aeration tank with a volume of 86 cum. Air shall be supplied through air blowers of capacity 90 cum/hr. At 0.5 kg/sqcm pressure fitted to 5 HP motor to the coarse bubble diffusers fitted at the bottom of the aeration tank.

3/ Overflow from the aeration tank shall be let into the settling tank having a volume of

21.50 cum. A recirculation pump is fitted to pump the sludge back to the aeration tank with the help of 2 HP pumps. Excess sludge shall be collected in the sludge holding tank of capacity

12.25 cum.

4/ Overflow from the settling tank shall be let into the treated water tank having a capacity of 27.50 cum, from which you shall pump the treated water through filter feed pumps of 5 HP capacity to PSF and ACF.

5/ The filtered water shall be disinfected using chlorine and stored in an overflow collection tank having a capacity of 141 cum for reuse in garden/flushing

 

Problem identification: The existing conventional treatment system with an activated sludge process contains several units with inadequate retention time in the aeration tank. The system was not properly working due to insufficient MLSS in the aeration tank. Running cost and maintenance cost was high due to lack of knowledge and understanding about the technology.

 

 

 

Fig (1): Typical Layout of the Sewage treatment plant at Sahana Clothing Company Private Limited, Kamanaickenpalayam

 

 

Units Size No of tanks
Collection Tank 3.50 m x 3.50 m x 3.26 m (LD) 1
Aeration Tank 5.80 m x 3.50 m x 4.26 m (LD) 1
Treated Water Tank 3.50 m x 3.50 m x 2.26 m (LD) 1
Settling tank 3.36 m dia x 2.44 m (LD) 1
Overflow collection Tank 7.93 m x 4.88 m x 3.65 m (LD) 1
Sludge Holding Tank 5.70 m x 2.15 m x 1.00 m (LD) 1

 

 

Table (1) Dimensions of Sewage Treatment Plant

 

 

1.3   Up-gradation of Existing Facility with OxyO Biofilm Technology

 

 

Biofilm treatment technology differs considerably from the activated sludge process, although the objective is to eliminate contamination in wastewater. One technique that uses microorganisms effectively reduces sludge production and eliminates human interference in biological treatment. It is necessary to ensure a high degree of purification by microorganisms to permit the reuse or release of treated water into water bodies.

 

Process Description

 

Collection Tank

 

The wastewater from the bar screen chamber flows into the collection tank having dimensions 3.50 m x 3.50 m x 3.26 m LD by gravity. The floor of the collection tank shall be fitted with spargers to ensure a complete mix of the untreated wastewater by supplying air through a dedicated air blower of a capacity of 25 cum/hr. at 0.35 kg/sqcm. pressure. The aeration mixes the wastewater to prevent settling of suspended solids and control odour.

Aeration Tank

 

The wastewater from the collection tank shall be pumped to the aeration tank at a constant flow rate of 6.25 cum/hr. Using the existing raw sewage pumps. The air shall be supplied through the existing air blowers of capacity 90 cum/hr. At 0.5 kg/sqcm pressure, the spargers fitted at the bottom of the aeration tank for uniform air distribution to fluidize immersed biofilm for biological treatment.

Biofilm immersed in wastewater in the aeration tank enhances the proliferation of biological activity in the tank. The organic matter in the wastewater is thus exposed to a powerful bacterial action and is rapidly decomposed.

Nitrification occurs in the aeration tank in this process having a retention time beyond 12 hours.\

 

Settling Tank

 

The overflow from the aeration tank shall be let into the existing settling tank having retention of 3 to 4 hours. The treated wastewater shall be let into the overflow collection tank.

 

The overflow collection tank will be provided with Ozonator for disinfection purposes for reuse in flushing and gardening.

 

 

2.     RESULT AND DISCUSSIONS

 

  1. Performance evaluation

 

The performance of the existing activated sludge process in terms of treatment was assessed through the removal efficiency. The conventional/ existing treatment process was not able to provide good results. After implementing OxyO technology, it was possible to achieve 90-95% efficiency of organic matter removal in the aeration tank, and there will be very minimal sludge form in the settling tank. The sludge can be skimmed off once in 3 months. Previously the industry use to buy freshwater from outside at 7 paisa/L; after up gradating the existing facility, the wastewater is being treated at 0.7 paisa/L

 

 

 

OxyO Technology Suspended Growth Process
Cell viability 3 times that of the suspended growth process. A consortium of bacteria grown in suspended growth has a high rate of mortality. Aerobic bacteria are susceptible to

variation in flow or BOD.

Sludge production is low compared to any

another process.

Only extended aeration process produces

digested sludge.

No requirement of seeding bacteria to

stabilize the plant.

Need to inoculate with sufficient

a consortium of bacteria to start the plant.

Reduced maintenance cost High maintenance cost
No chemicals used Chemicals & filters used

 

 

2.     Maintenance cost comparison of the sewage treatment plant at Sahana Clothing Company Private Limited

 

 

 

Equipment

Conventional

treatment process

 

Cost

 

OxyO

 

cost

Raw sewage transfer pump 2 HP 2,000/- 2 HP 8,500/-
 

 

Air Blowers

5 HP (Working+ Standby) common blowers were used for both collection &

aeration tank

 

21,500/-

 

5 HP (Working+ Standby)

Dedicated air blower for aeration tank

 

21,500/-

 

Air Blowers

1.5 HP (Working+ Standby)

Dedicated air blower for collection tank

6,500/-
Clarifier 1 HP 4,300/- Eliminated 0
Sludge

recirculation pump

 

2 HP

 

8,500/-

 

Eliminated

 

0

 

Disinfection

Chlorine dosing – 0.5 HP (every month

procurement)

 

500/-

Ozonator- 1 HP one time investment  

1,300/-

Filter feed pump 5 HP 3,500/- 5 HP 1,300/-
Treated water for Reuse

Did not reuse

5HP 1300/-
Electricity bill Every month 40,300/- Every month 40,400/-
 

Labour payment

 

Operating the plant

 

15,000/-

No operating person

Required (Minimal)

 

5000/-

Chlorine for disinfection Required After

chlorination

 

20,000/-

 

Eliminated

 

0

Miscellaneous cost  

Every month

 

4,500/-

 

Every month

 

833/-

Total maintenance cost  

Every month

79,800/- or more  

Every month

46,233/- –

maximum

 

 

 

Fig. (a) Aeration tank after implementing OxyO technology

Fig. (b) Treated water from settling tank with Nitrates( not visible to the eye)

Fig. (c) Treated water after Ozonization

 

 

Miscellaneous expenses: (Conventional Method)

1.       Change media in filters –

(Sand and Carbon minimum 2 years once) – 3000/2

 

15,000

2.       Clean and change the Diffusers (Yearly) – 10,000
3.       Remove Sludge 20,000
4.       Maintenance of Pumps and Blowers                                                    – 10,000
Total    – 55,000

 

Miscellaneous expenses – (OxyO)

 

In the conventional treatment, it did not treat water enough to reuse as the removal of Nitrates was not happening.

 

OxyO – We have treated the water for reuse and recovered most of the water apart from leakages and evaporation.

 

 

The Treated water cost per litre – Rs. 46,233 per month / 30 days = Rs. 1541
To treat 150 KLD                        – Rs. 1541 / 150000 = Rs. 0.010 – 1 paise / litre
 

Total savings made per month water bought at .07 paise / ltr x 150000 = Rs. 10,500

 

 

 

Total cost per month – Rs. 315000 /- (+)
Cost to run the plant (Older process) – Rs. 79800/- (+)
Total cost to treat (OxyO)   – Rs. 46,233 /- (-)
 

Savings –                                –

 

Rs. 348,567 /-

 

Using OxyO technology, a minimum of 3 Lakhs is saved per month.

Conclusion

 

we have analyzed This case study analysed the results obtained from the conventional treatment process and OxyO treatment process.

 

  1. In the conventional treatment process, the aeration tank capacity was inadequate to hold one full day. We have achieved the same by connecting collection and aeration tanks. A dedicated blower is provided to supply air  provided in the collection tank.
  2. In OxyO technology, sludge recirculation and clarifier mechanisms are eliminated.
  3. Very minimal sludge is produced in the settling tank; the operator  can skim off once in 3 months which in turn reduces
  4. In the conventional treatment plant, the process was incomplete, and a further process was required to treat the water for reuse. But using OxyO technology, we have completed the process using the same.
  5. We have achieved 100 % odourless treated water, which is well below the standards of pollution control.
  6. Chlorination for disinfection is replaced with ozone, so the treated water is safer to reuse and is chemical.
  7. Maintenance cost reduced by 50 % and also simple to
  8. Eliminated the usage of consumables in the process. The only consumable is electricity.

 

 

Editor-in-chief

Arun Karunakaran

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