SAFOP Study for Waste Water Treatment Plant of North Field East Onshore Project

SAFOP Study for Waste Water Treatment Plant of North Field East Onshore Project Epc‐1

M/s. iFluids Engineering & Consultancy WLL has been awarded the project to carry out the Safety & Operability study (SAFOP) for Waste Water Treatment Plant for North Field East onshore Project EPC‐1. The project is sponsored by Qatar Gas (QG) and Qatar Energy – RLIC wherein Chiyoda-Technip Joint Venture (CTJV) is the main EPIC contractor & METITO Qatar WLL is nominated as a subcontractor for Engineering works.

As a part of EPC activities, SAFOP study is carried out for electrical facilities of the Waste Water Treatment Plant for North Field East Project. To learn more on What is SAFOP Study? Click Here. It mainly covers modification works at the existing WSS-01 S/Stn No 1 A190/A310 to electrical facilities at New WWTP S/Stn A10/A20 and New WWTP S/Stn MCC Switchboard.

The overall objective of this project is to design a treatment plant capable of treating Domestic Sewage of total capacity of 15,830 m3/day. At total plant capacity of 15,830 m3/day, the BOD load is 4305.76 kg BOD/day, and the COD load is 9323.87 kg COD/day.

The Plant is designed into 3 biological streams (5277 m3/day) to enable partial operation; at initial stages each stream is capable to handle 30% of the coming flow (1585 m3/day) with the same design values organic loading in terms of BOD, TSS, TKN, alkalinity and TDS. Minimum organic loading at 30% of the coming flow (1585 m3/day) is 431.12 kg/day BOD related, 933.565 kg/day COD related, 351.87 kg/day TSS related, 63.4 kg/day TKN related, 396.25 kg/day alkalinity related and 724.345 kg/day TDS related.

The pressurized domestic sewage from the lift station shall be equalized in an aerated Balancing Tanks, to handle the peak shock loads and homogenize the wastewater, plus regulating the downstream feeding over 24 hours. The WWTP shall have Pre‐treatment units consisting of combined screening, grit and grease removal system; all this in one unit called Compact Inlet Headworks. After the pre‐treatment, sewage will be split via distribution chamber into three secondary treatment streams (Aeration Tanks and Secondary Settling).

The biological treatment system consists of three streams; Aeration Tanks and Secondary Settlement Tanks which are provided to achieve the final treated water quality. The treated sewage from Secondary Settling Tanks will be further flowed in Chlorine Contact Tanks for disinfection purposes, the disinfected water will be further polished through Pressure Sand Filters. The filtered water will be conveyed to Treated Sewage Effluent Tanks. From these tanks, part of the treated water will be used for backwashing the Pressure Sand Filters, plant washdown demands; while the other part will be pumped for Irrigation and to Tanker Filling Stations.

The excess sludge produced from the Secondary Settling Tanks will be collected in aerated Sludge Holding Tanks; whereas the sludge gets detained for a certain time, and then dewatered using Belt Filter Press. The dewatered sludge from Belt Press units will be stabilized, whereas powdered lime will be mixed with the dewatered sludge to stabilize the dewatered sludge, and will then be disposed to designated location in RLIC with 18% solids content. Water produced from Belt Press will be drained to local pit and recycled back to Balancing Tanks.

The objective of municipal waste water treatment is to extract pollutants, remove toxicants, neutralize coarse particles, and kill pathogens so that quality of discharged water is improved to reach the permissible level of water to be reused for irrigation purposes.

The main reasons for treating sewage are:

  • To protect public health.
  • To preserve the environment.
  • To provide efficient reuse of treated sewage.

Sewage contains suspended and soluble contaminants, which are normally classified in two main groups:

  • Organic
  • Inorganic

Both organic and inorganic solids can be broken down further into Suspended Solids and Dissolved Solids. Suspended solids are mainly organic in nature, are visible and can be removed from the sewage by physical/mechanical means e.g. screening and sedimentation. The strength of the sewage is often determined by measuring the amount of oxygen consumed by bacteria in biodegrading the organic matter.

The treatment process used in the design of this sewage treatment plant is called Extended Aeration, which is basically an activated sludge process. The main concept of this process is to create an ideal environment to ensure that an adequate number of microorganisms are available to feed on the organic matter in the sewage. This results in a complete conversion of the organic matter into stable end ‐products.

All incoming gravity sewer flows are connected to each lifting stations; EPC‐3‐LS, EP2- LS, EPC-1N-LS, flow from each of the three lift stations is pumped to be finally pumped to the main forwarding lifting station EPC‐1S‐LS. From this lift station, the raw sewage will be transferred by two raw sewage rising mains to the WWTP area plot.

The WWTP included the following;

Balancing Tanks, Air Blowers for Balancing Tanks, Compact Inlet Headwork, Distribution Chamber, Aeration Tanks, Secondary Settling Tanks, Air Blowers for Aeration Tanks, Sodium Bicarbonate Dosing System, Chlorine Contact Tanks, Sodium Hypochlorite Dosing System, Pressure Sand Filters, TSE Tanks, Tanker Filling Station, Secondary Sludge Pumps, Sludge Holding Tanks, Air Blowers for Sludge Holding Tanks, Belt Filter Press Units, Lime System, Odour Control Unit, Drain Pit and Drain Pumps and Scum Drain Pit and Scum Drain Pumps.