CN1257118C - Integrated treatment process for discharge of gas well production wastewater up to standard - Google Patents

Abstract

The present invention relates to an integrated processing technology for wastewater extracted from a gas well to achieve the effluent standard, and belongs to a processing technology for wastewater of oil-gas fields. The integrated processing technology comprises the following processes: a technology unit of the compounding and emulsion breaking reaction, a technology unit of the air flotation and separation by a Nikuni pump, a technology unit of a coarse filtering pool, a technology unit of a biofilm reactor with a hydrolysis and acidification reluctance floating bed, a technology unit of a biofilm reactor with an aerobic moving bed, and a technology unit of an aeration biologic filtering pool. The present invention has the advantage that the wastewater pollutant removing efficiency is high; the running expense is low; the management is simple; the present invention is suitable for the manufacture of integration equipment, and the integration equipment is arranged on the fields of medium and small natural gas exploitation stations. The equipment has good removing effect on main pollutants of water organic matters (COD, BOD), petroleum oil, ammonia nitrogen, sulphides, suspended substances (SS), and the like exploited from gas stations.

Description

Integrated treatment process for discharge of gas well production wastewater up to standard

technical field

The invention relates to an integrated treatment process for the up-to-standard discharge of gas well production wastewater, which belongs to the oil and gas field wastewater treatment technology

Background technique

At present, the treatment of gas well produced water is mainly based on physical and chemical methods, mainly focusing on the removal of refractory organic matter. Generally, the scale is small, the treatment cost is high, and the pollutants treated are relatively simple. Most of them are still in the research stage and have not been used in real production engineering. At present, no biological treatment technology has been adopted in the domestic experimental research on the treatment of gas well produced water.

Sedimentation-blowing-ozonation technology is used to treat gas well water. The main pollutants in the water are organic matter, oil, sulfide and suspended solids. In the case of 14.5mg/L, better results have been achieved.

The internal electrolysis method is used to remove COD in the gas field water. The internal electrolysis method uses the fact that some components in the wastewater are easily oxidized and some components are easily reduced. When these components with different properties meet and there is a conductive medium, the chemical reaction will occur. A method of wastewater treatment that is carried out spontaneously. The influent COD value is 250-600mg/L, the pH is controlled at 4.0, and the effluent COD is less than 150mg/L under the condition of HRT1.0h. This method has a slow reaction rate and is greatly affected by the pH value, and is not suitable for the treatment of high-concentration wastewater.

Coagulation sedimentation-micro-electrolysis-oxidation-adsorption method is used to treat produced water from gas wells. The whole experiment is carried out in the laboratory, which can be divided into 4 steps. The first step is to determine the optimal treatment formula of coagulation settlement through orthogonal experiments: polyferric sulfate (PFS) 400mg/L, pH value is 7; the second step is at pH Under the condition of 1, Fe/C micro-electrolysis for 25 minutes; the third step of bleaching powder oxidation, the dosage is 8g/L, and the oxidation time is 20h; the fourth step is activated carbon adsorption, the dosage of activated carbon is 8mg/L, and the equilibrium time is 40min, which can make the raw water The COD value dropped from 1,567mg/L to 150mg/L, and other pollution indicators reached the national comprehensive sewage discharge level 2 standard, but the method is complicated to operate and the treatment cost is high.

The combined method of hydrogen peroxide oxidation and activated carbon adsorption is used to treat the produced water of gas wells. On a small scale, the dosage of H ₂ O ₂ is 0.8mL/100mL of wastewater, the dosage of activated carbon is 4g/L, and the total removal rate of COD can reach 81.8 %.

In foreign countries, there are few specific studies on the produced water of gas wells, and generally focus on the produced water of the entire oil (gas) field. For example, the continuous flow activated sludge treatment system treats the produced water of Southwest Oilfield in the United States. Under the conditions of sludge retention time (SRT) 20d and mixed liquid suspended solids concentration (MLSS) 730mg/L, the petroleum hydrocarbons in the wastewater ( TPH) removal rate reaches 98-99%. A small-scale reverse osmosis-wetland treatment process is used to treat oil production wastewater, and the removal rates of conductivity and total dissolved solids (TDS) of the whole process reach 94% and 95% respectively. Coarse granulation + membrane bioreactor combination process is used to treat oilfield produced water. Large particles in wastewater are removed through coarse granulation, and dissolved pollutants are removed through membrane bioreactor. The hydraulic retention time (HRT) is 12h. Under certain conditions, the removal rates of COD, TOC, phenol and ammonia nitrogen reached 65%, 80%, 65% and 40%, respectively, and the final process effluent COD and TOC were 230 and 55mg/L.

Contents of the invention

The purpose of the present invention is to provide an integrated treatment process for the standard discharge of gas well production wastewater, which has high efficiency in removing pollutants in gas well production wastewater and low operating costs.

The present invention is realized through the following technical scheme, for the waste water containing petroleum hydrocarbons, sulfides, ammonia nitrogen and suspended solids discharged in the gas well exploitation process, the integrated treatment process of up-to-standard discharge is characterized in that it includes the following process:

1. Coagulation and demulsification reaction process unit: at a stirring speed of 80-100 rpm, add coagulation and demulsification agent polyferric sulfate or polyaluminum chloride to the produced wastewater, and the coagulation and demulsification agent has a mass percentage concentration of 5 ~10%, when the COD _cr content in gas well production wastewater is 2000~50000mg/L, the dosage of coagulation demulsifier is 50~500mg/L, and the reaction time is controlled at 3~10min;

2. Nickel air pump air flotation separation process unit: vertical flow air flotation separation process is adopted, the water flow of the pump is controlled at 0.1-0.2m ³ /h, the suction volume accounts for 5%-10% of the influent water, and the contact area of the air flotation tank stays 3 to 5 minutes, the residence time in the separation zone is 30 to 60 minutes; the overflow removes scum, and the clear water is drawn out from the perforated pipe at the bottom of the pool;

3. Coarse filter tank process unit: the filter material in the pool has a particle size gradation of 5-10mm, 2-5mm granular filter material, the height of the filter material layer is 0.7-1.0m, and the cushion layer is gravel, with a height of 0.2-0.3 m, the operating filtration rate of the filter is 6-8m/h;

4. Process unit of hydrolytic acidification anaerobic floating bed biofilm reactor: light biofilm particle filler is added to the reactor. Based on the bulk volume of the filler, the ratio of the amount of filler to the total volume of the tank is 50% to 70%. When the COD _cr of wastewater entering the biofilm reactor is 400-2000mg/L, the operating organic load is 1-5kgCOD _cr /(m ³ tank capacity d), and the hydraulic retention time is 5-8h;

5. Process unit of aerobic moving bed biofilm reactor: light biofilm particle filler is also added to the moving bed biofilm reactor, and an aeration device is installed at the bottom of the reactor. The ratio of the amount added to the total volume of the tank is 50% to 70%, the operating organic load is 0.5 to 2kgCOD _cr / (m ³ tank capacity d), the hydraulic retention time is 5 to 8h, and the ratio of aeration to water inflow is 3 ~10:1;

6. Biological aerated filter process unit: The biological aerated filter is set to operate in two stages in series. The water flow of the first stage filter adopts the downflow type, and the second stage adopts the upflow type. The filter is filled with high surface area ceramsite particles Filler, ceramsite particle size 2-5mm, filler layer thickness 1.5-1.8m, cushion layer made of gravel, thickness 0.2-0.3m, filter filtration rate controlled at 0.3-1.0m/h, contact time 1-3h, recoil Strength 8～12m/h.

The invention has the advantages of high waste water pollutant removal efficiency, low operation cost and simple management, and is suitable for being made into integrated equipment and installed on the site of small and medium-sized natural gas production stations. The equipment has a good removal effect on organic matter (COD, BOD), petroleum, ammonia nitrogen, sulfide, suspended solids (SS) and other major pollutants in the produced water of gas wells. After treatment, the effluent can reach the second-level discharge standard in the national "Comprehensive Wastewater Discharge Standard GB8978-1996".

Description of drawings

Fig. 1 is a process block diagram of the present invention.

Detailed ways

Taking the treated wastewater volume of 3m ³ /d as an example, the specific implementation method of the patent of the present invention is as follows:

1. The waste water produced by the gas well passes through the storage tank and enters the coagulation and demulsification reaction tank by gravity at a rate of 0.125m ³ /h. The stirring speed of the reaction tank is 100 rev/min, the coagulation demulsifier added is polyferric sulfate, and the demulsifier ratio mass percentage concentration is 5%. The dosage of the demulsifier is determined by the beaker test according to the concentration of COD _cr in the wastewater. For example, when the wastewater COD _cr =5000mg/L, the dosage concentration of the demulsifier is 200mg/L, and the reaction time is controlled at 5min.

2. The waste water after coagulation and demulsification is pumped up with the Niconi air flotation pump and poured into the vertical flow air flotation tank. The flow rate of the air flotation pump is controlled at 0.125m ³ /h, and the suction volume accounts for 7% of the water inflow. The contact zone of the air flotation tank stays for 5 minutes, and the separation zone stays for 60 minutes.

3. After air flotation, the waste water enters the coarse filter tank. The filter operation filtration rate is 6m/h.

4. The effluent filtered by the coarse filter flows into the hydrolytic acidification anaerobic floating bed biofilm reactor by gravity. The reactor is fed with light biofilm particle filler, the ratio of the filler to the total volume of the tank is 50% (based on the bulk volume of the filler), the operating organic load is 3kgCOD _cr / (m ³ tank capacity d), hydraulic The residence time is 7h.

5. The hydrolyzed and acidified anaerobic floating bed biofilm reactor produces waste water that is hydrolyzed and acidified, and enters the aerobic moving bed biofilm reactor by gravity. A perforated tube aeration device is installed at the bottom of the moving bed biofilm reactor; the volume ratio of light biofilm particle filler is 50%, the operating organic load is 1.0kgCOD _cr /(m ³ tank capacity d), and the hydraulic retention time is 7h , The ratio of aeration volume to water intake volume is 3:1.

6. The effluent from the aerobic moving bed biofilm reactor flows into the biological aerated filter by gravity. The biological aerated filter is set to operate in two stages in series, the water flow of the first stage of the biological aerated filter adopts the downflow type, and the second stage of the biological aerated filter adopts the upflow type. The particle size of the ceramsite particle filler filled in the filter is 2-5mm, the thickness of the filler layer is 1.8m, the cushion layer is made of gravel, the thickness is 0.3m, the filtration rate of the filter is controlled at 1.0m/h, and the total contact of the two-stage filter is 3h. The recoil strength is 12m/h.

7. The outlet water from the second-stage biological aerated filter flows into the clear water tank by itself, and the treated water is pumped up and discharged from the clear water tank through the outlet pump. The flow rate of the outlet pump is 0.125m ³ /h. From time to time, the backwash pump is used to draw water from the biological aerated filter to backwash the biological aerated filter or the coarse filter.

Implementation Effect:

According to above implementation mode, the treatment effect of technique of the present invention is:

Treated water volume: 3m ³ /d, water temperature greater than 20°C;

Main water quality indicators of raw water: COD _cr ＝2000～30000mg/L, BOD ₅ ＝1300～7000mg/L, ammonia nitrogen＝29.14～117.3mg/L, petroleum＝90.3～109mg/L, sulfide＝1.84～6.6mg/L , suspended solids (SS) = 150 ~ 250mg/L.

The treated effluent meets the secondary discharge standard stipulated in the national "Sewage Comprehensive Discharge Standard GB9878-1996". The main water quality indicators of the actual effluent: COD _cr ＝50～145mg/L (standard is ≤150mg/L), BOD ₅ ＝1.6～12.8mg/L (standard is ≤30mg/L), ammonia nitrogen＝0.69～3.95mg/L ( Standard is ≤25mg/L), petroleum = 0.56～5.47mg/L (standard is ≤10mg/L), sulfide=0.0013～0.0342mg/L (standard is ≤0.5mg/L), suspended solids (SS) =10.0～30.0mg/L (standard is ≤150mg/L).

Claims (1)

1. An integrated treatment process for the up-to-standard discharge of gas well production waste water, which is for the up-to-standard discharge treatment of waste water containing petroleum hydrocarbons, sulfides, ammonia nitrogen and suspended solids discharged in the gas well exploitation process, and is characterized in that it includes the following process: 1). Coagulation and demulsification reaction process unit: at a stirring speed of 80-100 rpm, add coagulation and demulsification agent polyferric sulfate or polyaluminum chloride to the produced wastewater, and the mass percentage concentration of coagulation and demulsification agent is 5-10%, when the COD _cr content in gas well production wastewater is 2000-50000mg/L, the dosage of coagulation demulsifier is 50-500mg/L, and the reaction time is controlled at 3-10min; 2).Nickini air pump air flotation separation process unit: vertical flow air flotation separation process is adopted, the water flow rate of the pump is controlled at 0.1~0.2m ³ /h, the suction volume accounts for 5%~10% of the influent water, the contact area of the air flotation tank Stay for 3 to 5 minutes, and stay in the separation zone for 30 to 60 minutes; the overflow removes scum, and the clear water is drawn out from the perforated pipe at the bottom of the pool; 3).Coarse filter tank process unit: the particle size distribution of the filter material in the tank is 5-10mm, 2-5mm granular filter material, the height of the filter material layer is 0.7-1.0m, the cushion layer is gravel, the height is 0.2- 0.3m, the operating filter rate of the filter is 6-8m/h; 4). Process unit of hydrolytic acidification anaerobic floating bed biofilm reactor: light biofilm particle filler is added to the reactor, and based on the bulk volume of the filler, the ratio of the amount of filler to the total volume of the tank is 50% to 70% , when the COD _cr of the wastewater entering the biofilm reactor is 400-2000mg/L, the operating organic load is 1-5kgCOD _cr /(m ³ pool capacity d), and the hydraulic retention time is 5-8h; 5).Aerobic moving bed biofilm reactor process unit: light biofilm particle filler is also added to the moving bed biofilm reactor, and an aeration device is installed at the bottom of the reactor. Based on the bulk volume of the filler, the filler The ratio of dosage to the total volume of the tank is 50% to 70%, the operating organic load is 0.5 to 2kgCOD _cr /(m ³ tank capacity d), the hydraulic retention time is 5 to 8h, and the ratio of aeration to water inflow is 3～10:1; 6). Biological aerated filter process unit: The biological aerated filter is set to operate in two stages in series. The water flow of the first stage filter adopts the downflow type, and the second stage adopts the upflow type. The filter tank is filled with high surface area ceramsite Granular filler, ceramsite particle size 2-5mm, filler layer thickness 1.5-1.8m, cushion layer made of gravel, thickness 0.2-0.3m, filter filtration rate controlled at 0.3-1.0m/h, contact time 1-3h, reverse The impact strength is 8~12m/h.

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