Design Approach for Sewage Treatment Plant: A Case Study on STP at Trendz Whispering Woods Apartment Bogadi, Mysuru

Abstract

The project details with the study of domestic waste water collected by Apartment Trendz Whispering Woods Bogadi, Mysuru and sub sequent design of sewage treatment plant. This study focuses on the sewage generation in the Trendz apartment and modification in the conventional sewage treatment plant by introducing OxyO technology. The total sewage generated was estimated 120 KLD per day considering total population in the apartment. The sample water collected from the conventional sewage treatment plant and characterization for the same has been done and result has been provided (pH, Total suspended solids, Ammonia, Nitrate, COD & BOD). The sewage treatment plant is quiet necessary to receive the domestic and commercial waste and removes the material with pose harm from the general public. The objective is to produce an environmentally sage fluid waste stream and solid waste (or Treated sludge) suitable from the disposal of reuse from OxyO technology and comparative study of the conventional and OxyO technology. 

Keywords: Attached growth process (AGP), Suspended growth process (SGP), Domestic wastewater, Nitrification, Denitrification. Moving bed biofilm reactor (MBBR) 

 

1. Introduction

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

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 it offers 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 the biological treatment technology (OxyO treatment technology). The is an attached growth process that utilizes complete biological process and can be operated in just one tank. It works as an collection, aeration, equalization, and biological treatment in a single tank through a timed control sequence, which makes it environmentally friendly technology. An OxyO system and is only used in multi-basin applications to remove the maximum quantity sludge and reuse the rest for vegetation purpose.

 

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 same but dimensions vary. Sewage treatment plant with different capacities as shown in the figure(1).  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. In short notice these DIY kits can be supplied to the end users which needs with no specialised skills to start their biological process plants. The aim is to minimise 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 one year 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 nine wastewater treatment plants set up are 2.50 KLD to 120 KLD, all performing to the expectations of the customers. They are our referrals. The treated wastewater in some places is partially reused for gardening, irrigation and flushing in toilets. 

 

 

Fig (1). OxyO technology -Sewage treatment plants implemented with varying capacities and sizes based on available space at the site

 

1.2 Advantages of our Treatment Technology

1/ No chemical consumption incurred in the STP

2/ Existing facility utilized with simple modification. The flow to the treated water tank shall be regulated from the equalization tank. The treated water tank shall be modified into combined aeration and settling tank by constructing a baffle wall.

3/ The blower to the aeration tank shall be a dedicated air supply for biological treatment in the aeration tank. 

4/ The Sewage Treatment Plant already commissioned need not be shut down for improvement in the process

5/ Design based on retaining bio mass in the aeration tank for increased biological activity – viable cell count which will never be sluggish.

6/ Sludge production completely minimized. Odor automatically controlled as a result of improved biological activity. 

7/ Treated water after disinfection meets all statutory standards and fit for disposal 

8/ The quantity of sludge slurry generated may not exceed 30 L per day fully digested. This slurry can be directly used for horticulture without further treatment.

9/ Lowered maintenance cost.

 

1.3 CHALLENGE 

Existing treatment process of capacity 120 KLD at trendz apartment

The existing MBBR/Conventiaonal process for treating sewage having capacity to hold 120 KLD. The treatment unit designed based on the population at the trends apartment. The process involved in existing sewage treatment plant as follows,

 

1/ From bar screen chamber wastewater flows into oil & grease chamber and over flows into Equalisation tank of capacity 25 cum. The wastewater shall flow into the equalisation tank bypassing the O&G chamber

2/ The wastewater from the equalization tank shall be pumped to the final water tank, UF treated water tank and sludge holding tank to give a combined holding capacity of 97.60 cum

3/ The combined tanks of item 2 shall be aerated by placing diffusers in the tank connected to the existing blowers

4/ The raw sewage from the tanks shown in item 2 shall be pumped to the 4 FBR tanks

5/ The overflow from the FBR tanks shall be let into the existing settling tank.

6/ The sludge from the settling tank shall be pumped to an appropriate facility 

7/ The overflow from the settling tank shall be let into the chlorination tank for disinfection tank

8/ The disinfected treated water shall be let into the pre collection tank of capacity 30 cum

9/ The treated water from pre collection tank shall be filtered and sent for reuse/disposal

 

Problem identification:  The existing MBBR/conventional treatment system contains number of units with in adequate retention time in aeration tank. Choice of the media was wrong where in case the media remains immersed in wastewater and enhances proliferation of biological activity in the aeration tank. System was not properly working due to insufficient media in the aeration tank. Running cost and maintenance cost was high due to lack of knowledge and understanding about the technology. Although it was designed as MBBR, yet to work on principle of MBBR. 

Fig (2): Flow Diagram of Sewage treatment plant at Trends apartment, Mysore

 

Units

Size

No of tanks

Pre collection tank

1.7 m x 4.0 m x 3.0 m (LD)

1

Chlorine dosing tank

1.7 m x 4.0 m x 3.0 m (LD)

1

UF treated water tank

1.7 m x 4.0 m x 3.0 m (LD)

1

Settling tank

2.25 m x 2.25 m x 3 m (LD)

2

FBR 1

1.6 m x 1.6 m x 4.0 m (LD)

2

FBR 2

1.6 m x 1.6 m x 4.0 m (LD)

2

Equalization tank

2.16 m x 4.0 m x 3.0 m (LD)

2

Final water tank

1.35m x 3.4 m x 3.0 m (LD)

2

 

Table (1). Technical specification of sewage treatment plant

 

RESULT AND DISCUSSIONS

 

Performance evaluation 

The performance of existing MBBR 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 removal in aeration tank and there will be very minimal sludge form in the settling tank and these sludge can be skim it off once in 3 months. The result obtained from the OxyO technology was meeting all the KSPCB norms which is mentioned in the table 2 and efficiency of removal is mentioned on the table 3.

 

Table 2. Treated water characteristics -OxyO sewage treatment technology

Sl.No.

PARAMETER

Units

RAW SEWAGE (mg/L)

TREATED WATER (mg/L)- oxyo technology

KSPCB standards (mg/L) (june 1st 2019)

1

pH

(mg/L)

7.47

8.06

6.5-9.0

2

Total suspended solids

(mg/L)

180

4

<50

3

Biological oxygen demand 

(mg/L)

200

5

20

4

Chemical oxygen demand

(mg/L)

599

28

-

5

Ammonical Nitrogen

(mg/L)

19.88

11.99

-

6

Total nitrogen

(mg/L)

36.91

18.82

-

7

Total coliform

MPN/100 ml

-

161

<1000

 

 

Table 3. Removal efficiency from the sewage treatment technology

Sl. no

Sewage treatment technology

Removal Efficiency (%)

Running cost & maintenance cost

1

(Existing technology) MBBR/ Conventional 

40-50%

High

OxyO technology

100%

Reduced by 90%

 

 

 

 

Cost comparison of sewage treatment plant at trendz apartment

 

Equipments

Conventional treatment process

Cost  

OxyO

cost

Blowers  

20 HP (10 HP Working+ 10HP Standby)

6,00,000/- (for 2 numbers)

10 HP (5 HP Working+ 5 HP Standby)

3,00,000/- (for 2 numbers)

Pump  

Raw sewage pump-1.5 HP

25,000/-

Eliminated-Through Gravity to the tank

0

Sludge return pump

1.5 HP

25,000/-

Eliminated (air lift used –connected from blower)

0

Disinfection  

Chlorine dosing -every month

35,000/-

Ozonator- one time investment

30,000/-

Filter media

Cleaning once in 6 month

10,000/-

Not required- very minimal sludge production 

0

Labour payment

Operating the plant

12,000/-

No operating person required

0

Filters & filter pump

Required After chlorination 

Around 1 lakh

Not required

0

Electricity bill 

Every month 

55,785/- or more 

Every month 

25,000/- -maximum 

 

 

 

 

 

 

Fig (e) Revamping work at existing sewage treatment plant of capacity 120 KLD

 

 

Fig (f) After implementing OxyO sewage treatment technology

 

Fig (g) sample of water after complete treatment from STP  

Fig (2).  Treated water sample result from the OxyO technology

 

 

Conclusion 

In this case study the results obtained from conventional treatment process and OxyO treatment process were analysed. 

In the conventional treatment process 15 tanks were used for the treatment. In comparison to the conventional process, OxyO technology utilized only four tanks as aeration tank, settling tank de-nitrification and treated water tank for the complete treatment process and 90-95 % removal efficiency was achieved.

From the results obtained there was very minimal sludge produced in the settling tank which can be skimmed off once in 3 months which in turn reduces manpower.

100 % odourless treated water.

Maintenance cost reduced by 90-95 %

There were no chemical utilized in the process.

 

OxyO Technology 

Suspended Growth Process 

Cell viability 3 times that of suspended growth process. 

Consortium of bacteria grown in suspended growth has high rate of mortality. Aerobic bacteria very sensitive to variation in flow or BOD. 

Sludge production low compared to any other process. 

Only extended aeration process produces digested sludge. 

No requirement of seeding bacteria to stabilize the plant. 

Need to inoculate with sufficient consortium of bacteria to start the plant. 

Maintenance cost reduced up to 90-95% 

High maintenance cost 

No chemicals used 

Chemicals & filters may be used 

 

Arun Karunakaran 

Founder | OxyO 

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