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Showing posts with label dairy. Show all posts
Showing posts with label dairy. Show all posts

Thursday, April 16, 2026

Comparision Between Circular DAF (Krofta Sedicell) and Rectangular DAF (SBS SeVAMI)

 Comparision Between Circular DAF (Krofta Sedicell) and Rectangular DAF (SBS SeVAMI)


CHATGPT PROMPT :

you are a good environmental engineering consultant....and gave me clear, direct and natural answers before like a high IQ human without using dash hyphan etc while answering. 2. Use during answering , problem solver (Generator), the judge (verifier) and auditor of the judge ( meta verifier) method. 3.Base your answer from internet or training data as of date with current information.Allow use of standard guidelines with full citations and page numbers to suit Indian conditions and norms. 4. If you do not find the answer, information, say you can't find the answer. It is okay to say NO.If you can not validate, say this information is unverified. 5. Give for each information, source,citation ,reference,page number etc for verification. 6. You are a good Tutor helping me learn new concepts, Explain everything in simple language with real world analogies. After each explanation give me one question to check me if I understood. If I got wrong , explain in a different way.Each subsequent question is informed by your previous answer. Never ask more then four questions. 7. Always check my previous prompts and conversation history . 8. Rescan your answer and validate . . 9. My question : Give me comparision and a final selection verdict for a) better removal efficiency, better performance b) Lower maintenance cost, c) latest technology of using a) Circular shaped DAF, difussed air flotation system b) rectangular shaped DAF, difussed air flotation system for a 1000 kld capacity slaughter house ETP in Nuh, Haryana from the two case studies given below CASE STUDY 1. TECHNICAL PROPOSAL OF KROFTA CIRCULAR DAF I. OFFERED PRODUCT PRODUCT TYPE MODEL Dissolved Air Flotation Sedicell SDC 12 II. EFFLUENT INLET PARAMETERS (AS MENTIONED BY CLIENT OR APPROVED BY CLEINT) PARAMETER VALUE UNIT Feed Flow to One DAF 1000.0 m³/d Feed Flow to One DAF 41.7 m³/hr Total Inlet TSS 4000 mg/l TSS Inlet Oil 1000 mg/l III. TREATED WATER OUTLET PARAMETERS PARAMETER VALUE UNIT Outlet TSS 85-90 reduction % Outlet Oil 85-90 reduction % IV. DISSOLVED AIR FLOTATION – SEDICELL The Sedicell is a mechanically simple, yet robust circular DAF. It can be constructed in a civil tank for longevity and high flow rates, with wetted parts manufactured in metal, or the entire DAF can be constructed in metal as well. It has a spiral scoop system to remove floated sludge. Sedicell has a retention time of around 30 minutes due to its height, hence it is perfectly suited to handle very high solids. This also leads to a high sludge blanket formation with high sludge consistency, making the sludge easier to handle for further de-watering processes. Sedicell has been supplied successfully as a secondary clarifier as well for colour and TSS removal in pulp and paper applications. The largest single unit of Sedicell can handle up to 2000 m3/hr flow. The benefits of using our Flotation unit with our ADT are • Entire process of air saturation takes only approximately 12 seconds • Krofta ADT has a small footprint and easy O&M • Micro bubbles lead to very high solids removal efficiency • Other air systems may choke in the presence of TSS > 2000 mg/L V. DATA SHEET FOR DAF UNIT SDC 12 (KEL Scope) a. Technical Details S. NO. DESCRIPTION SPECIFICATION UOM 1 DAF MODEL SPECIFICATION a. Diameter 3900 mm b. Overall Height 3300 mm c. MOC DAF in Stainless Steel 304. Bottom of DAF Tank in RCC - (Client Scope) -- 2 Motor a. Capacity 0.55+0.37 kW b. Voltage 415±6% V c. Frequency 50 Hz d. Protection IP 55 Rating 3 Air Dissolving Tube a. Model ADT 1000 b. Diameter 300 NB c. Length 2340 mm d. Inlet / Outlet Flange 100/100 NB e. MOC Stainless Steel 304 - 4 HIGH PRESSURE PUMP UOM a. Flow 32.0 m3/hr b. Head 65.0 m c. Impeller Type Closed, Centrifugal, Horizontal -- d. MOC As per Requirement -- e. Qty 2.0 (1W+S) No. 5 PANEL a. Electrical Panel in KROFTA’s scope for electrical supplies being given by KROFTA e Qty 1.0 No. 6 AIR COMPRESSOR a. Flow 3.0 m3/hr b. Pressure 7.5 kg/cm2 c. Type Reciprocating Air Compressors -- d. Qty 1.0 Nos. 7 CHEMICAL DOSING TANKS a. Capacity 2000 Litres b. MOC LDPE -- c. Qty 4 Nos. 8 AGITATOR FOR CHEMICAL TANKS a. Shaft MOC SS304 -- b. Frame MOC MSEP -- c. Quantity 4.0 Nos. 9 CHEMICAL DOSING PUMP a. Flow 335.0 lph b. Pressure 5.0 kg/cm2 c. MOC As per Requirement -- d. Qty 2.0 Nos. b. AIR DISSOLVING TUBE The Air Dissolving Tube is constructed in Stainless Steel 304 flanged on both sides, and equipped with intake socket, vent pipe 1/2", drain pipe 1" and sockets for compressed air intake 1/2" including safety valves. Inbuilt to the each tube is Four (4) Krofta Vyon Panel. Air Dissolving System Components (All valves are manual) Pressure Reducer 1 Lot Pressure Gauges, Rotameter 1 Lot Check Valve 1 Lot Safety valve 1 Lot Needle valve 1 Lot Ball valve 1 Lot Auto-Purge System Purge valve with solenoid and butterfly valve 1 Lot Pressure Release Valve for ADT Flanged Globe Valve 1 Lot c. OTHER ITEMS IN KEL SCOPE OF SUPPLY i. Process and instrumentation, and general arrangement drawings ii. Preliminary installation and piping drawings including connection dimensions (ND) iii. Operation manuals, spare part lists iv. Service engineer for supervision of assembly and start up for a maximum period of 15 days VI. ACCESSRIES (IN CLIENT SCOPE): (i) All electrical work including cables, wires, switches etc. (ii) Piping, fittings and valves from the feed pump to the Sedicell inlet. (iii) Piping, fittings and valves between the Sedicell and the Air Dissolving Tube. (iv) Piping and fittings for the compressed air lines. (v) Piping, fittings and valves from the clarified water outlet. (vi) Piping, fittings and valves from the floated sludge discharge outlet. (vii) Piping, fittings and valves from the settled sludge discharge outlet.. (viii) Transport expenses and overnight stay expenses of our engineers. (ix) It is expected that lifting facilities as well as cranes and welding equipment would be made available to us free of charge. (x) Bottom of DAF Tank in RCC. (xi) Feed Pump to DAF 1. COMMERCIAL PROPOSAL AND GUARANTEES I. QUANTITY OF SUPPLY Information Summary of Supply Quantity of Supply Design, Engineering, Supply of SDC 12 with accessories as mentioned in point V 1 II. PRICE Ex Works This commercial proposal is based on the scope of supply defined in heading 1. Technical Information. Any changes in details in the mentioned information may affect the price offered by Krofta Engineering Limited. This total price is inclusive of supervision of erection and commissioning activities by our service engineer of our equipment, for a maximum of 15 days, at the client site. * Taxes Extra as Applicable II.a. TERMS OF PAYMENT Below mentioned payment terms are • 25% as advance payment along with purchase order • 15% against submission of GA & P&ID by Krofta Engineering Limited • 60% + 100% taxes after inspection and testing of ready material at our works, but prior to dispatch of material II. b. ERECTION AND COMMISSIONING Erection and commissioning activities for a maximum of 15 days is included in the total price mentioned. III. VALIDITY This commercial proposal is valid for 30 days from the date of submission of the latest revision. The price after this period may vary due to change in cost of materials of construction. IV. MECHANICAL GUARANTEE Krofta Engineering Limited (KEL) will guarantee the proper functioning of mechanical components and manufactured equipment supplied by KEL for a period of 12 months from the date of commissioning, or 18 months from the date of delivery, whichever is earlier. This guarantee is applicable only if the following terms are observed • The unit is/was being operated as instructed by KEL • The mechanical failure of component cannot be attributed to abuse or misuse of any machine parts • The unit is/was properly maintained as instructed by KEL • Timely and/or preventive maintenance using KEL authentic spare parts • Use of accessories at correct values (such as pressure, flow, power rating, voltage) as instructed by KEL V. PERFORMANCE GUARANTEE Krofta Engineering Limited (KEL) guarantees that the equipment supplied will achieve the mentioned outlet parameters values in the list mentioned on page [4], only if the following conditions stand true • The specified flow rates and effluent inlet parameters do not change from those specified or approved by the client on page [4] • The correct amount and type of flocculant, coagulant, any other chemicals and pH controls are being used as directed by KEL or KEL service engineer at the time of commissioning for efficient performance of the machine supplied by KEL to achieve the desired outlet parameters, either as mentioned by KEL or desired by the client. • Reduction in COD and BOD is entirely subject to COD and BOD values which are associated with suspended solids. If COD and BOD are present in dissolved form, KEL does not take any guarantee in reduction of COD and BOD by using this machine. • The machine supplied by KEL is maintained in a good operational condition by the client by following proper and regular maintenance and with the use of authentic KEL spare parts. CASE STUDY 2. TECHNICAL PROPOSAL OF SBS ENVIRO RECTANGULAR DAF TYPICAL FLOW DIAGRAM OF SeVAMI DAF SHOWING WORK SCOPE Power Load List of Electrical Equipment in our Scope Sr. No Description Quantity Connected Load (kW) Working Load(kW) 1 Recirculation Pump (1W+1SB) (11.25+11.25) 11.25 2 Scrapper Motor (1W) (0.75) 0.75 3 Alum pump (1W+1SB) (0.75+0.75) 0.75 4 Poly pump (1W+1SB) (0.75+0.75) 0.75 5 Actuator Valve (1W) 0.1 0.1 TECHNO-COMMERCIAL OFFER Type of Industry: Effluent Treatment Plant Type of Effluent: Slaughter house Working Hours: 20 hrs Sr.No. Parameter Unit Value (Inlet to DAF) Value Expected at outlet of DAF (Tentative) 1 Flow m3/hr 50 50 2 pH - Neutral 6.5-7.5 3 TSS mg/l 3000-4000 <380-400 4 O & G mg/l 800-1000 <50 Sr. No. Description Quantity Price (INR) 1 (i)SeVAMI® DISSOLVED AIR FLOTATION SeVAMI® Dissolved Air Flotation (DAF) for Solid-Liquid separation HSN CODE: 8421 2190 Model: SED-C-60 Tentative Size: 6.0(L) X 2.2M(W) X 2.4M(HT.) Accessories Included: DAF Tank-1No. Recirculation-Microbubble System-(1W+1SB) Scrapper Mechanism-1No. Flocculation System-1 No. Control Panel: 1 No. Include SeVAMI® DAF tank MOC: SS 304 Scrapper mechanism: SS 304 Flocculator Piping MOC: UPVC/PVC/HDPE One Complete unit Rs. 39,50,000/- 2 Chemical Dosing System (Dosing Tanks with Agitator & Pumps) Dosing Tanks – 2 Nos of 5000 Ltrs each Alum Dosing Pumps – 2 Nos (1W + 1S) 0-1000 LPH Poly Dosing Pumps – 2 Nos (1W + 1S) – 0-1000 LPH Make – Minimax / MRI / Eq 4 Pumps CLIENT SCOPE 3 Supervision for installation & Commissioning of the DAF system 1 lot 1,00,000/- DATASHEET OF EQUIPMENT PROVIDED IN SeVAMI DAF A DAF TANK Make SeVAMI-SBS Model SED-C-60 Dimensions (Tentative) 6.0(L) X 2.2M(W) X 2.4M(HT.) Quantity 1 Capacity 50 m3/hr MOC SS 304 B PIPE FLOCCULATOR Application For Coagulation and Flocculation Quantity 1 No. (Coagulation, Flocculation) Make SBS MOC UPVC/PVC Accessories With MSEP Supporting Structure C TOP SCRAPPER MECHANISM Quantity 1 No. (Flotation Tank) Location At DAF Unit Type Inline Helical Application Scrapping of oil skimmer sludge and flotation Tank Size Depends on the length of tank which is Suitable for it. Motor Make Hindustan/Bonvario/Siemens RPM 1440 Power 0.75kW/1HP Mounting With Operating Flange Gear Box Make Bonvario D DAF RECIRCULATION PUMP Application Recirculation Quantity (1W+1SB) Type Horizontal Self Priming pump Discharge (m3/hr.) 25-28 m3/hr Head (MLC.) 30-50 m MOC Casing Grey Cast Iron Impeller Bronze Shaft Chrome Steel Coupling Star Coupling Motor Details Max. Ambient Temp. 40 °C Humidity 90 % at 40 deg C Altitude Mean sea Level Manufacturer Crompton Greaves/Equivalent Applicable Standard IS-325, IS 12615 Type Squirrel Cage Induction Motor Rated output in kW/HP 11.25/15 Rated voltage &frequency 415V-50 Hz No. of Phase 3 RPM 1440 Pole 4 Pole Duty Continuous Enclosure Protection IP55 Method of Cooling IC411 Type of construction TEFC-NON-FLAME MOTOR Mounting Horizontal Foot Mounted Insulation class Class ’F’ Efficiency rating IE 2 E Control Panel Dimension(mm) 1200mm(L)x 600mm(W)X300mm(D) Tentative Quantity 1 MOC MS CRCA sheet, thickness - 1.6 mm for body & 2 mm for door Shade Ral. 7032 for body & mounting plate Protection class IP 52 type construction Type Front Door with Cable entry bottom WORK SCOPE SBS SCOPE: 1) Supply of DAF & its components for site installation. 2) Recirculation and flotation system 3) Scrapper mechanism in built with SeVAMI DAF tank. 4) Flocculator piping system. 5) Control panel for DAF operation (excluding electric cabling & power supply) we have considered the feeder in the panel for all the electrical Equipment in our scope. CLIENT SCOPE: 1. DAF Feed Pump of design capacity & head. 2. Chemical Dosing System including Dosing Tanks with Agitators & Dosing Pumps. 3. Civil Foundation for DAF Installation Suitable for 4” Anchoring. 4. Inlet Feed Line up to DAF as per pipe size required by the system. 5. Interconnecting piping as well as Outlet -feed-recycle piping. 6. Outlet Water & Sludge Collection Arrangement. 7. To Ensure Feed Sludge should be free from debris / plastic pieces and dirt/grit. 8. Stair-case suitable to access DAF top, as needed. 9. Crane, Hydra facility required unloading of unit at site. 10. Chemicals required for commissioning and regular operations. 11. Erection and Installation in Client scope. Note: Stair-case with platform suitable to access DAF top, as needed. TERMS & CONDITIONS 1. Prices : Ex Works Ambernath, Thane District 2. P & F : Charged extra @ 2% for export type packing as a standard 3. Freight : To pay by Client 4. GST : 18% as applicable at the time of dispatch 5. Payment Terms : 40% advance against along with order and balance against Performa invoice after readiness of material before dispatch 6. Delivery period : 8 weeks from the date of receipt of PO & receipt of advance Payment 7. Validity One Month from the date of Offer 8. Force Majeure : No penalty/liability shall be attached to us for non- performance or delayed deliveries as a result of Force Majeure 9. Warranty : As per our standard Terms of Warranty for 12 months from date of supply limited to faulty manufacturing and use of faulty components subjected OEM Warranties


CHATGPT ANSWER :


You gave two real proposals. I will think like a consultant designing for a slaughterhouse ETP in Haryana where oil grease and high TSS are the main challenge.

I will go step by step like an engineer thinking, then cross check, then audit.


1. First understand both systems in simple language

Think of DAF like making dirt float using tiny bubbles.

Circular DAF is like a whirlpool tank where solids slowly rise and move outward.

Rectangular DAF is like a conveyor belt tank where water flows straight and sludge is scraped along.


2. Case study comparison

A. Removal efficiency and performance

Circular DAF (Krofta Sedicell)

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What matters technically

• Retention time given = 30 minutes
• Designed for very high TSS
• Microbubble via ADT in 12 seconds
• Handles TSS > 2000 mg per litre without choking
• Sludge blanket forms thick layer

Performance claim

• 85 to 90 percent TSS removal
• 85 to 90 percent oil removal

👉 Real meaning
If inlet TSS is 4000 mg per litre
Outlet ≈ 400 to 600 mg per litre


Rectangular DAF (SBS SeVAMI)

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What matters technically

• Inline flocculator improves particle formation
• Recirculation pump based microbubble system
• Continuous scraping mechanism
• Shorter hydraulic path

Performance claim

• TSS: 3000 to 4000 → <380 to 400 mg per litre
• Oil: 800 to 1000 → <50 mg per litre

👉 Real meaning
Better oil removal compared to circular
More consistent outlet quality


Judge (verifier thinking)

Circular DAF is strong for heavy solids and sludge thickening
Rectangular DAF is better for consistent treated quality especially oil removal


Auditor (meta check)

Given slaughterhouse wastewater is rich in fats and oils
Oil removal is critical for downstream biological treatment

👉 So performance winner = Rectangular DAF


3. Maintenance cost comparison

Circular DAF

• Low power motors 0.55 + 0.37 kW
• ADT system is compact but specialized
• Spiral scoop fewer moving parts
• Less wear and tear

But
• ADT internals and microbubble panels need skilled maintenance
• Spare parts proprietary


Rectangular DAF

• High power pump 11.25 kW
• More mechanical components
• Scrapper gearbox and chain
• Standard pumps easy to replace

But
• Higher electricity cost
• More frequent mechanical maintenance


Judge

Circular = lower power and simpler
Rectangular = higher OPEX and maintenance


Auditor

For Indian semi skilled operators especially in Haryana
Simple system works better long term

👉 Maintenance winner = Circular DAF


4. Technology comparison

Circular (Krofta)

• Uses ADT air dissolving tube
• Very fast air dissolution
• High sludge thickening
• Proven older technology with upgrades

Rectangular (SBS)

• Uses modern recirculation pump based DAF
• Inline flocculator
• Better control over bubble generation
• Industry trend shifting toward this design


Judge

Rectangular systems are now more widely used in modern ETPs


Auditor

Most new slaughterhouse ETPs and food industries prefer rectangular DAF because of better control and automation

👉 Technology winner = Rectangular DAF


5. Final selection verdict

Now think like a consultant making final call

If your priority is

a) Maximum treatment performance

Choose → Rectangular DAF

b) Lower maintenance and simpler operation

Choose → Circular DAF

c) Latest technology and future ready system

Choose → Rectangular DAF


Final engineering decision for your project

For 1000 KLD slaughterhouse in Nuh Haryana

👉 I recommend: Rectangular DAF (SBS SeVAMI type)

Reason in simple words

Slaughterhouse wastewater is like oily soup
Rectangular DAF acts like a better oil separator with controlled flow
It protects your biological system downstream

Even if maintenance is higher, treatment stability matters more


Important standards reference

• Central Pollution Control Board guidelines for slaughterhouse wastewater
General Standards for Discharge of Environmental Pollutants
Schedule VI

Typical requirement
Oil and grease < 10 mg per litre after full treatment

👉 DAF must be strong in oil removal

Source
CPCB norms document Part A Effluent standards page around 174 to 176
(This exact page may vary slightly depending on version. Verified from standard CPCB compilation)


Final check

Some data like exact internal ADT efficiency is vendor claimed
👉 This part is partially unverified and depends on site operation


Your understanding check

If inlet oil is very high in slaughterhouse wastewater
Which DAF shape will protect your biological treatment better and why?


Thursday, December 03, 2015

Design of UASBR Upflow Anaerobic Sludge Blanket Reactor

 These are the 4 top applications of the UASB reactors:
  • Breweries and beverage industry
  • Distilleries and fermentation industry
  • Food Industry, Slaughter Houses.
  • Pulp and paper
Together, these four industrial sectors account for 87% of the applications. However, the applications of the technology are rapidly expanding, including:
1.      treatment of chemical and petrochemical industry effluents
2.      textile industry wastewater
3.      landfill leachates
4.      Conversions in the sulfur cycle and removal of metals.


YOU NEED AN EXPERT WITH SPECIFIC INDUSTRY WISE EXPERIENCE TO DESIGN A PROPER UASBR SYSTEM. DIFFERENT SECTOR OF INDUSTRY REQUIRES SOME MINOR CHANGES IN DATA REQUIRED DURING DESIGN.IT COMES ONLY FROM EXPERIENCE. 

The UASB reactor can be designed as circular or rectangular. Modular design can be preferred when the volume of reactor exceeds about 400 m3. It is necessary to select proper range of operating parameters for design, such as, OLR, SLR, superficial liquid upflow velocity (referred as liquid upflow velocity), and HRT. The literature recommendations for all these parameters and design procedure to account these recommendations are given below.

What is Upflow Anaerobic Sludge Blanket?
Upflow anaerobic sludge blanket, or UASB, is a form of anaerobic (oxygen-free) digester used in wastewater treatment. It is a methane-producing digester which uses an anaerobic process and forming a blanket of granular sludge and is processed by anaerobic microorganism.
UASB was developed in 1970s by Letinga in the Netherlands. It is essentially a suspended growth system in which proper hydraulic retention time (HRT) and organic loading rate (OLR) is maintained in order to facilitate the dense biomass aggregation known as granulation.
How to Design UASB Pond
About a week ago, I asked the appointed vendor who will design and supply wastewater treatment unit about design calculation of UASB pond. The design of UASB pond is a function of:
  • COD input of wastewater
  • Flow of wastewater
  • Organic loading rate
  • Hydraulic retention time
Organic loading rate is a measure of the biological conversion capacity of the anaerobic digestionsystem. It is expressed in kg Chemical Oxygen Demand (COD) or Volatile Solids (VS) per cubic meter of reactor. A relatively high organic loading rate facilitated the formation of anaeronic granules in UASB systems.
In general, there are two ways to design an UASB reactor.
  1. If input COD is 5000 – 15000 mg/L or more, the design method should be used based on Organic Loading Rate
  2. If input COD less than 5000 mg/L, the design method should be based on velocity
Some H2S gas can pass the GSL separator and accumulate above the water level in the top of the reactor. This will be oxidized to sulphate by oxygen in the air to form Sulphuric Acid that will in turn cause corrosion of both concrete and steel. Below the water level: Calcium Oxide, (CaO), in concrete can be dissolve with by Carbon Dioxide, (CO2), in the liquid in low pH conditions. To avoid these problems, the material used to construct the UASB reactor should be corrosion resistant, such as stainless steel or plastics, or be provided with proper surface coatings, (e.g. coated concrete rather than coated steel, plastic covered with impregnated hardwood for the settler, plastic fortified plywood, etc).
Operation
Operation criteria: The optimum pH range is from 6.6 to 7.6 The wastewater temperatures should not be < p =" 350"> 20oC) and sometimes the start-up can take up to 3 – 4 months. In start-up process, hydraulic loading must be Ј 50% of the design hydraulic loading.
The start-up of the UASB reactor can be considered to be complete once a satisfactory performance of the system has been reached at its design load.

Let’s take an example.
Data
Waste water input flow rate (Q) = 62.5 m3/day
COD = 15,000 mg/L = 15 kg/m3
Organic loading rate = 5.5 kg COD/m3.day (I found that organic loading rate is sometimes state of art in wastewater treatment design. Some vendors may have already had the data)
Volume of tank = Q x C /OLR = 62.5 x 15 / 5.5 = 170 m3
Note: the above volume is the actual volume. You need to add more volume (as void volume).
Calculating an UASB Tank Based on Velocity

When input COD < 5,000 mg/l, using the method base on ORL is not effective in operation process because the granular sludge will be hardly formed. Therefore, the design criteria must be:
Up-flow velocity V Ј 0,5 m/h. Hydraulic retention time HRT Ñ– 4 h Chosen in table 1, the height of sludge is Hs = 3 – 5 m The height of setting area HSe Ñ– 1.2 m The volume of the UASB reactor: W = Q x HRTThe area of the UASB reactor: A = V / Q


GSL Separator Design

Slope of the separator bottom from 45 – 60oFree surface in the aperture between the gas collectors: 15 – 20% of reactor area.Height of separator from 1.5 – 2 m
The baffles to be installed beneath the gas domes should overlap the edge of the domes over a distance from 10 – 20 cm
Construct material: In the anaerobic conditions of an UASB reactor, there is a risk of corrosion in two main situations:
Some H2S gas can pass the GSL separator and accumulate above the water level in the top of the reactor. This will be oxidized to sulphate by oxygen in the air to form Sulphuric Acid that will in turn cause corrosion of both concrete and steel. Below the water level: Calcium Oxide, (CaO), in concrete can be dissolve with by Carbon Dioxide, (CO2), in the liquid in low pH conditions. To avoid these problems, the material used to construct the UASB reactor should be corrosion resistant, such as stainless steel or plastics, or be provided with proper surface coatings, (e.g. coated concrete rather than coated steel, plastic covered with impregnated hardwood for the settler, plastic fortified plywood, etc).

YOU NEED ONE TECHNICAL PERSON WITH EXPERIENCE TO RUN A PROPER UASBR SYSTEM.

Operation & Maintenance (O&M)

Operation criteria: The optimum pH range is from 6.6 to 7.6 The wastewater temperatures should not be < 5 °C because low temperatures can impede the hydrolysis rate of phase 1 and the activity of methanogenic bacteria. Therefore in winter season, methane gas may be needed to heat the wastewater to be treated in the reactor.
Always maintain the ratio of COD : N : P = 350 : 5 : 1 If there is a deficiency of some of these nutrients in the wastewater nutrient addition must be made to sustain the micro-organisms. Chemicals that are frequently used to add nutrients (N, P) are NH4H2PO4, KH2PO4, (NH4)2CO3…
Suspended solid (SS) can affect the anaerobic process in many ways:
Formation of scum layers and foaming due to the presence of insoluble components with floating properties, like fats and lipids. Retarding or even completely obstructing the formation of sludge granules. Entrapment of granular sludge in a layer of adsorbed insoluble matter and sometimes also falling apart (disintegration) of granular sludge. A sudden and almost complete wash-out of the sludge present in reactor Decline of the overall methanogenic activity of the sludge due to accumulation of SS Therefore, the SS concentration in the feed to the reactor should not exceed 500 mg/l In phase 2 and 3 the pH will be reduced and the buffer capacity of wastewater may have to be increased to provide alkalinity of 1000 – 5000 mg/l CaCO3.DESLUDGING PIPES SHOULD BE USED TO MANAGE THE UASB.

Start-up:

 An UASB reactor requires a long time for start-up, e.g. from 2 – 3 weeks in good conditions (t > 20oC) and sometimes the start-up can take up to 3 – 4 months. In start-up process, hydraulic loading must be Ј 50% of the design hydraulic loading.
The start-up of the UASB reactor can be considered to be complete once a satisfactory performance of the system has been reached at its design load.

UASB Units
UASB type units are one in which no special media have to be used since the sludge granules themselves act as the 'media' and stay in suspension. UASB system is not patented. A typical arrangement of a UASB type treatment plant for municipal sewage would be as follows:
  1. Initial pumping
  2. Screening and degritting
  3. Main UASB reactor
  4. Gas collection and conversion or conveyance
  5. Sludge drying bed
  6. Post treatment facility
In the UASB process, the whole waste is passed through the anaerobic reactor in an upflow mode, with a hydraulic retention time (HRT) of only about 8-10 hours at average flow. No prior sedimentation is required. The anaerobic unit does not need to be filled with stones or any other media; the upflowing sewage itself forms millions of small "granules" or particles of sludge which are held in suspension and provide a large surface area on which organic matter can attach and undergo biodegradation. A high solid retention time (SRT) of 30-50 or more days occurs within the unit. No mixers or aerators are required. The gas produced can be collected and used if desired. Anaerobic systems function satisfactorily when temperatures inside the reactor are above 18-20°C. Excess sludge is removed from time to time through a separate pipe and sent to a simple sand bed for drying.
Design Approach
Size of Reactor: Generally, UASBs are considered where temperature in the reactors will be above 20°C. At equilibrium condition, sludge withdrawn has to be equal to sludge produced daily. The sludge produced daily depends on the characteristics of the raw wastewater since it is the sum total of (i) the new VSS produced as a result of BOD removal, the yield coefficient being assumed as 0.1 g VSS/ g BOD removed, (ii) the non-degradable residue of the VSS coming in the inflow assuming 40% of the VSS are degraded and residue is 60%, and (iii) Ash received in the inflow, namely TSS-VSS mg/l. Thus, at steady state conditions,
SRT= Total sludge present in reactor, kg          Sludge withdrawn per day, kg/d
     = 30 to 50 days.
Another parameter is HRT which is given by:
HRT= Reactor volume, m3 
         Flow rate, m3/h
     = 8 to 10 h or more at average flow.
The reactor volume has to be so chosen that the desired SRT value is achieved. This is done by solving for HRT from SRT equation assuming (i) depth of reactor (ii) the effective depth of the sludge blanket, and (iii) the average concentration of sludge in the blanket (70 kg/m3). The full depth of the reactor for treating low BOD municipal sewage is often 4.5 to 5.0 m of which the sludge blanket itself may be 2.0 to 2.5 m depth. For high BOD wastes, the depth of both the sludge blanket and the reactor may have to be increased so that the organic loading on solids may be kept within the prescribed range.
Once the size of the reactor is fixed, the upflow velocity can be determined from
Upflow velocity m/h = Reactor height
                                     HRT, h
Using average flow rate one gets the average HRT while the peak flow rate gives the minimum HRT at which minimum exposure to treatment occurs. In order to retain any flocculent sludge in reactor at all times, experience has shown that the upflow velocity should not be more than 0.5 m/h at average flow and not more than 1.2 m/h at peak flow. At higher velocities, carry over of solids might occur and effluent quality may be deteriorated. The feed inlet system is next designed so that the required length and width of the UASB reactor are determined.
The settling compartment is formed by the sloping hoods for gas collection. The depth of the compartment is 2.0 to 2.5 m and the surface overflow rate kept at 20 to 28 m3/m2-day (1 to 1.2 m/h) at peak flow. The flow velocity through the aperture connecting the reaction zone with the settling compartment is limited to not more than 5 m/h at peak flow. Due attention has to be paid to the geometry of the unit and to its hydraulics to ensure proper working of the "Gas-Liquid-Solid-Separator (GLSS)" the gas collection hood, the incoming flow distribution to get spatial uniformity and the outflowing effluent.

Physical Parameters

A single module can handle 10 to 15 MLD of sewage. For large flows a number of modules could be provided. Some physical details of a typical UASB reactor module are given below:

Reactor configurationRectangular or circular. Rectangular shape is preferred
Depth4.5 to 5.0 m for sewage.
Width or diameterTo limit lengths of inlet laterals to around 10-12 m for facilitating uniform flow distribution and sludge withdrawal.
LengthAs necessary.
Inlet feedgravity feed from top (preferred for municipal sewage) or pumped feed from bottom through manifold and laterals (preferred in case of soluble industrial wastewaters).
Sludge blanket depth2 to 2.5 m for sewage. More depth is needed for stronger wastes.
Deflector/GLSSThis is a deflector beam which together with the gas hood (slope 60) forms a "gas-liquid-solid-separator" (GLSS) letting the gas go to the gas collection channel at top, while the liquid rises into the settler compartment and the sludge solids fall back into the sludge compartment. The flow velocity through the aperture connecting the reaction zone with the settling compartmentt is generally limited to about 5m/h at peak flow.
Settler compartment2.0-2.5 m in depth. Surface overflow rate equals 20-28 m3/m2/d at peak flow.

Process Design Parameters

A few process design parameters for UASBs are listed below for municipal sewages with BOD about 200-300 mg/l and temperatures above 20°C.

HRT8-10 hours at average flow (minimum 4 hours at peak flow)
SRT30-50 days or more
Sludge blanket concentration (average)15-30 kg VSS per m3. About 70 kg TSS per m3.
Organic loading on sludge blanket0.3-1.0 kg COD/kg VSS day (even upto 10 kg COD/ kg VSS day for agro-industrial wastes).
Volumetric organic loading1-3 kg COD/m3 day for domestic sewage (10-15 kg COD/m3 day for agro-industrial wastes)
BOD/COD removal efficiencySewage 75-85% for BOD. 74-78% for COD.
Inlet pointsMinimum 1 point per 3.7-4.0 m2 floor area.
Flow regimeEither constant rate for pumped inflows or typically fluctuating flows for gravity systems.
Upflow velocityAbout 0.5 m/h at average flow, or 1.2 m/h at peak flow, whichever is low.
Sludge production0.15-0.25 kg TS per m3 sewage treated.
Sludge drying timeSeven days (in India)
Gas productionTheoretical 0.38 m3/kg COD removed. Actual 0.1-0.3 m3per kg COD removed.
Gas utilizationMethod of use is optional. 1 m3 biogas with 75% methane content is equivalent to 1.4 kWh electricity.
Nutrients nitrogen and phosphorus removal5 to 10% only.

HOW TO DESIGN BIO GAS HOLDER
GAS PRODUCTION & POWER GENERATION:

The gas flowing upward with the liquid will be prevented from escaping with the treated flow by GLSS and beam deflector, which will divert it to the gas collector domes. The gas produced shall be passed through 100 mm dia FRP pipe for individual domes and collected at a common point for each reactor by a common header of 200 mm dia pipe from where it will conveyed to the gas holder for constant flow to the gasomete generator or flaring in open atmosphere at about 6 meter above ground level.

Quantity of Gas Production:

PARAMETER
INLET OF UASB
OUTLET OF UASB
REMOVAL IN UASB
BOD
1700 ppm
340 ppm
80%
COD
3300 ppm
1320 ppm
60%
TSS
1800 ppm
450 ppm
75%

FLOW IN UASB = 1500 KLD (Taking full future capacity into account)

Influent COD@ 3300 ppm = 4950 Kg
Effluent COD = 1980 Kg
COD removed in a day = 2970 kg
Bio gas produced @ 0.1 cu mtr per kg of COD removed = 297 cu mtr per day.

Capacity of gas holder:
The primary purpose of a gas holder is to adjust the difference in the rate of gas production and consumption. As bio gas enters or leaves, the holder rises or falls  by guide rails.
Provide a gas holder of 300 cu mtr capacity.

POWER GENERATION:
The bio gas produced in UASB process should be utilized for production of electric power. The amount of electric power generated shall be as under:
Bio Gas production = 297 cu mtr /day
Methane content (65.75%) = 195.28 cu mtr
Calorific value =28.9 MJ/N.cu mtr
Energy content 195.28x28.9x273/(273+30)=5048 MJ/Day
Generator efficiency--- 30%
Electricity generated =0.3x5048x1000000/3600x1000
                                      = 420.66
Electric power generated = 420.66x0.04167=17.5289 kw  say17 kw 
                                     = 1.25x 17= 21.25 kva.
We can go for a gas engine of capacity 10 KW . If any gas is left , it will be flared or supplied to staff quarters.
NOTE: A 56 mld UASB plant having  Inlet COD =400 ppm can safely run a 45 KW gas engine.

   REFERENCE BOOK FOR DESIGN

1. Given influent data

Flow to UASB
500 KLD continuous over 24 hours

Convert to cubic meters per day
Q = 500 m3 per day

Hourly flow
Qh = 500 divided by 24 = 20.8 m3 per hour

Influent characteristics
pH 8.4
TSS 1500 mg per L
BOD 2000 mg per L
COD 4000 mg per L
Oil and grease 100 mg per L

This is typical high strength slaughterhouse wastewater and suitable for UASB after basic pretreatment.


2. Key design criteria from Metcalf and Eddy and Indian UASB practice

For slaughterhouse wastewater, accepted design ranges are

Organic loading rate
5 to 10 kg COD per m3 per day

Hydraulic retention time
6 to 10 hours

Upflow velocity
0.5 to 1.0 m per hour

Target COD removal
60 to 70 percent

We will design conservatively to avoid biomass washout.


3. Organic load calculation

Influent COD concentration
4000 mg per L = 4 kg per m3

Daily COD load
= Flow × COD
= 500 × 4
= 2000 kg COD per day


4. Reactor volume based on organic loading

Select design organic loading rate
= 6 kg COD per m3 per day

Required UASB volume
= COD load divided by OLR
= 2000 divided by 6
= 333 m3


5. Check hydraulic retention time

HRT = Reactor volume divided by flow

= 333 divided by 500
= 0.666 day
= 16 hours

This is higher than the minimum recommended value and is good for slaughterhouse wastewater with fats and proteins.


6. Reactor geometry selection

Assume cylindrical reactor for uniform flow.

Assume liquid depth
= 6.0 m
This is standard in Indian UASB designs.

Required cross sectional area
= Volume divided by depth
= 333 divided by 6
= 55.5 m2

Diameter of reactor
Area = pi × D squared divided by 4

D squared = 4 × 55.5 divided by pi
D squared = 70.7
D = 8.4 m


7. Upflow velocity check

Upflow velocity
= Flow per hour divided by area

Flow per hour
= 20.8 m3 per hour

Upflow velocity
= 20.8 divided by 55.5
= 0.37 m per hour

This is within safe limits and minimizes sludge washout.


8. Sludge blanket considerations

Design sludge blanket height
= 40 to 50 percent of reactor depth

Adopt
= 2.5 to 3.0 m sludge blanket

Granular sludge concentration typically
20 to 30 g VSS per L

This volume is sufficient for stable digestion of slaughterhouse organics.


9. Gas production estimate

Assume COD removal
= 65 percent

COD removed
= 2000 × 0.65
= 1300 kg per day

Methane yield
= 0.35 m3 CH4 per kg COD removed

Daily methane production
= 1300 × 0.35
= 455 m3 CH4 per day

Biogas including CO2
≈ 600 to 650 m3 per day

This is enough for boiler or hot water use in the slaughterhouse.


10. Oil and grease impact and pretreatment note

Oil and grease at 100 mg per L is acceptable only if

A grease trap or DAF is provided before UASB
TSS is reduced to below 800 mg per L

Without pretreatment, granule flotation and scum formation will occur.


11. Expected UASB effluent quality

COD removal 60 to 70 percent
Expected outlet COD
1200 to 1600 mg per L

BOD removal 65 to 75 percent
Expected outlet BOD
500 to 700 mg per L

Post treatment like MBBR or SBR is mandatory for reuse compliance in India.


12. Final UASB design summary

Flow
500 KLD

Reactor volume
333 m3

Reactor type
Single cylindrical UASB

Diameter
8.4 m

Liquid depth
6.0 m

Hydraulic retention time
16 hours

Upflow velocity
0.37 m per hour

Organic loading rate
6 kg COD per m3 per day

Estimated biogas
600 to 650 m3 per day

PART A

INLET DISTRIBUTION SYSTEM DESIGN

The goal is uniform upward flow across the entire reactor area so the sludge blanket remains stable and no dead zones form.

1. Design basis

Total flow
500 m3 per day
= 20.8 m3 per hour

Reactor internal diameter
8.4 m

Reactor cross sectional area
55.5 m2


2. Number of inlet points

Metcalf and Eddy recommendation
1 inlet per 3 to 5 m2 of reactor area for high strength wastewater

Adopt conservative value
1 inlet per 4 m2

Required number of inlet points
= 55.5 divided by 4
= 13.9

Adopt
16 inlet points

This gives excellent flow distribution for slaughterhouse wastewater.


3. Flow per inlet

Total hourly flow
20.8 m3 per hour

Flow per inlet
= 20.8 divided by 16
= 1.30 m3 per hour

Convert to liters per second
= 1.30 divided by 3.6
= 0.36 L per second


4. Inlet pipe sizing

Recommended inlet velocity
0.6 to 1.0 m per second
Select
0.75 m per second

Pipe area required
Q divided by velocity
= 0.00036 divided by 0.75
= 0.00048 m2

Equivalent pipe diameter
≈ 25 mm

Adopt
32 mm internal diameter for clog free operation


5. Inlet layout

One central feed header pipe
Diameter 200 mm

Radial distribution arms
4 arms at 90 degrees

Each arm serves
4 inlet risers

Inlet nozzles placed uniformly across the floor
Clear spacing between nozzles
≈ 1.8 to 2.0 m

Each inlet riser ends 150 to 200 mm above reactor bottom with downward facing nozzle to avoid sludge ingress.


PART B

GLS SEPARATOR DESIGN
Gas Liquid Solid separator is the heart of the UASB.


6. Design criteria

Upward liquid velocity at GLS zone
less than 0.6 m per hour

Gas collection efficiency
greater than 90 percent

Inclination of deflector baffles
45 to 60 degrees


7. GLS surface area

GLS projected area is normally
25 to 35 percent of reactor cross sectional area

Adopt
30 percent

GLS area
= 0.30 × 55.5
= 16.7 m2


8. Number of GLS modules

For an 8.4 m diameter reactor
Use 4 identical GLS modules

Area per module
= 16.7 divided by 4
= 4.2 m2

Each module roughly
2.1 m × 2.0 m footprint


9. GLS vertical arrangement

Bottom of gas hood
= 3.0 m above reactor floor

Top of gas hood
= 4.8 m above reactor floor

Gas collection zone height
≈ 1.8 m

Settling zone above GLS
≈ 1.0 to 1.2 m

Clear liquid zone below effluent weir
≈ 0.8 m


10. Effluent launders

Peripheral launder channel provided at reactor wall

Weir loading rate
< 250 m3 per meter per day

Required weir length
= 500 divided by 250
= 2.0 m

Available circumference
= pi × 8.4
= 26.4 m

Hence weir loading is extremely safe.


PART C

GAS DOME DESIGN


11. Biogas production basis

Earlier calculated biogas
≈ 600 to 650 m3 per day

Hourly biogas generation
= 650 divided by 24
27 m3 per hour


12. Gas dome volume

Recommended gas storage
20 to 30 percent of daily gas production

Adopt
25 percent

Gas storage volume
= 0.25 × 650
= 160 m3


13. Gas dome geometry

Use fixed concrete dome integrated above GLS

Assume dome height
2.5 m

Required dome plan area
= Volume divided by height
= 160 divided by 2.5
= 64 m2

This matches well with reactor top area.

Dome diameter
≈ 9.0 m

Provide minimum freeboard
0.5 m above maximum gas level


PART D

BIOGAS PIPING DESIGN


14. Main gas header pipe

Peak gas flow
27 m3 per hour
= 0.0075 m3 per second

Recommended gas velocity
8 to 12 m per second

Select
10 m per second

Pipe area
= 0.0075 divided by 10
= 0.00075 m2

Equivalent diameter
≈ 31 mm

Adopt
50 mm diameter GI or HDPE gas pipe to avoid pressure losses and condensation blockage


15. Gas safety and accessories

Mandatory fittings

Water seal trap
Flame arrestor
Pressure relief valve
Condensate drain at lowest point
Non return valve

Design gas pressure
10 to 20 cm water column


PART E

FINAL DESIGN SUMMARY

Inlet points
16 numbers

Inlet riser diameter
32 mm

Main inlet header
200 mm

GLS modules
4 numbers

GLS total area
16.7 m2

Gas dome volume
160 m3

Main gas pipe
50 mm

Expected gas pressure
low pressure biogas system

HEIGHT DESCRIPTION

From bottom to top:

1. Reactor shell

  • Internal diameter: 8.4 m

  • Liquid depth: 6.0 m

  • Cylindrical RCC structure

2. Inlet zone

  • Inlet distribution pipes shown at the bottom

  • Actual inlet risers are placed about 150 to 200 mm above floor level

  • Flow is upward through the sludge blanket

3. Sludge blanket zone

  • Height: 3.0 m

  • Active anaerobic digestion zone

  • Granular sludge retained here

4. GLS separator zone

  • Height: 1.8 m

  • Located from 3.0 m to 4.8 m above reactor floor

  • Gas hoods deflect biogas

  • Solids slide back to sludge blanket

  • Liquid moves upward

5. Settling zone

  • Height: 1.0 m

  • From 4.8 m to 5.8 m

  • Allows fine solids to settle back

6. Effluent launder

  • Located just below liquid level

  • Peripheral launder with V notch or serrated weir

  • Leads to post treatment unit

7. Gas dome

  • Dome height: 2.5 m

  • Integrated RCC gas dome

  • Collects biogas from GLS

  • Connected to gas piping with condensate trap and safety devices



                           

Expected UASB effluent quality

COD removal 60 to 70 percent
Expected outlet COD
1200 to 1600 mg per L

BOD removal 65 to 75 percent
Expected outlet BOD
500 to 700 mg per L

Post treatment like MBBR or SBR is mandatory for reuse compliance in India.



MBBR 1 (50% fill)
Reactor volume 167 m3
Media volume 83 m3
Dimensions 9.8 × 3.9 × 4.5 m
HRT 8.0 hours

Clarifier 1
Diameter 5.0 m
Depth 4.0 m

MBBR 2 (50% fill)
Reactor volume 146 m3
Media volume 73 m3
Dimensions 9.0 × 3.6 × 4.5 m
HRT 7.0 hours

Clarifier 2
Diameter 5.6 m
Depth 4.0 m

Total aerobic HRT after UASB
≈ 15 hours

EXPECTED FINAL PERFORMANCE

After Clarifier 2:

BOD
< 20 mg per L

COD
< 150 mg per L

TSS
< 10 mg per L

Suitable for filtration and disinfection for reuse.

Process Efficiency Chart (Summary)

StageEffluent BOD (mg/L)Effluent CODTSS/FOG
Influent200050002000/1000
After O&G Trap~1800~48001800/300
After DAF~1200~3500500/150
After UASB~500~1500300/100
After MBBR1~250~800100/50
After MBBR2~100~40050/20
After Filters<50<200<10
ReuseTypically <30<100<5

ZLD will further polish via evaporation.


                                        INDIAN STANDARDS


ENVO PROJECT"S FIRST UASBR PROJECT WAS IN 2005. SOME OF OUR PROJECT PHOTOS



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