US-12623941-B2 - Method for removing ammoniacal nitrogen from hypersaline effluents through a consortium containing high-salinity-resistant heterotrophic nitrifying and aerobic denitrifying microorganisms

Abstract

The invention discloses a method to provide a consortium containing heterotrophic nitrifying and aerobic denitrifying microorganisms from an activated sludge originating from effluent treatment plants. The microbial consortium is capable of removing ammoniacal nitrogen from substrates with high salinity with superior efficiency. Thus, the microbial consortium from the described method can be applied to purify hypersaline effluents contaminated with nitrogen. Therefore, the use of the microorganism consortium provided to remove ammoniacal nitrogen from hypersaline effluents and a method therefor are also part of the scope of the invention.

Inventors

• Rodrigo Suhett De Souza
• HALINE BACHMANN PINTO
• Maira Paula DE SOUSA
• LARISSA QUARTAROLI
• CYNTHIA CANEDO DA SILVA
• LÍVIA CARNEIRO FIDÉLIS SILVA
• RICARDO DE ARAUJO CID DA SILVA

Assignees

• Petróleo Brasileiro S.A.—Petrobras
• UNIVERSIDADE FEDERAL DE VIÇOSA (UFV)

Dates

Publication Date

20260512

Application Date

20230809

Priority Date

20220810

Claims (7)

1. 1 . A method for removing ammoniacal nitrogen from hypersaline effluents through a consortium containing high-salinity-resistant heterotrophic nitrifying and aerobic denitrifying microorganisms, the method comprising: a) supplying an activated sludge from an effluent treatment plant for an effluent; b) providing a hypersaline aqueous effluent with salinity similar to the activated sludge from the effluent treatment plant; c) inoculating a reactor with the aforementioned activated sludge of item (a) and the hypersaline aqueous effluent of item (b) in a proportion ranging from 70:30 to 50:50; d) feeding and aerating the activated sludge for 4 hours, aerating for 3 hours, allowing to settle for 1 hour and discarding a supernatant for 4 hours; e) discarding 30% of the supernatant and completing a volume of the reactor with the effluent of item (b); f) weekly increasing the salinity of the effluent of item (b) with an addition of NaCl in a range of 5 g/L until a desired salinity between 100 and 200 g/L is reached, provided that there is no inhibition of nitrification, that is, a residual ammoniacal nitrogen is less than 20 mg/L; g) at salinities lower than 100 g/L, adding a source of carbon to the effluent of item (b) in order to ensure a minimum ratio of COD:NH 4 + from 20:1 to 40:1; or, at salinities greater than 100 g/L, maintaining a C:N ratio, measured as Total Organic Carbon (TOC)/NH 4 + , between 4 and 7; and h) maintaining a phosphorus source at a minimum NH 4 + /P ratio of about 5; wherein an alkalinity of the effluent of item (b) is maintained above 900 mg/L, a pH of the effluent of item (b) is maintained between 6.5 and 7.5 and a temperature of the effluent of item (b) is maintained between 27 and 33° C.
2. 2 . The method according to claim 1 , wherein the activated sludge comes from a production water treatment plant derived from oil exploration.
3. 3 . The method of claim 1 , wherein the effluent of item (b) is production water derived from oil exploration.
4. 4 . The method of claim 1 , wherein the source of carbon is ethanol and the phosphorus source is sodium tripolyphosphate.
5. 5 . The method of claim 1 , the salinity of the effluent of item (b) is greater than or equal to 50 g/L.
6. 6 . The method of claim 1 , wherein the temperature of the effluent of item (b) is maintained at about 30° C.
7. 7 . The method of claim 1 , wherein the pH of the effluent of item (b) is maintained at about 7.

Description

FIELD OF THE INVENTION The present invention pertains to the field of treatment of water, wastewater, sewage or muds and sludge. In particular, the invention fits the treatment of wastewater, particularly hypersaline effluents, contaminated with nitrogen compounds. BACKGROUND OF THE INVENTION During the process of extracting and processing oil, a large volume of water is consumed, with a high ratio of volume of water used per volume of oil processed. There is a large amount of water associated with the oil extracted, the so-called production water, which needs to be separated before the oil is distributed to the refineries. This water basically consists of a mixture of formation water, which is naturally present in the geological formation of the oil reservoir, and water injected into the reservoir for secondary oil recovery. The production water is transported to the surface along with the oil. Its composition is complex, containing in addition to carbonaceous compounds, heavy metals, dissolved solids and ions in solution with varying concentrations, such as chloride, sodium, calcium, magnesium, sulfide and ammonia. The characteristics of production water vary according to the geographic location of the exploration well, depth, geological formation, chemical composition of the extracted oil, chemicals used in the extraction and age of the exploration field. Wastewaters containing high concentrations of ammoniacal nitrogen can be toxic to aquatic life, cause eutrophication and oxygen depletion in the environment, negatively affecting water quality and aquatic microbiota. In this way, in accordance with environmental requirements, production water, before being discharged into the receiving body or being reused in the extraction process, must be treated. The treatment of production water occurs by physical, chemical, biological methods or by combinations of the same. The biological process has been widely used to remove ammoniacal nitrogen in non-saline effluents, mainly because of its lower cost. However, the presence of salt in effluent treatment plants is a limiting factor for biological water treatment processes, since salinity tends to affect the metabolic activity of microorganisms, reducing their growth and the oxidation rates of ammoniacal nitrogen. With the increase in oil exploration in the pre-salt layer in Brazil, the treatment processes of production water will face effluents with increasingly high salinity levels, which may limit the treatment with biological purification processes. Given this scenario, ensuring the biological treatment process of production water in conditions of high salinity is a challenge. Accordingly, the adaptation of the microbiota and the identification of parameters that allow the development of operational procedures to maintain the removal of ammonia in saline and hypersaline effluent treatment systems are necessary for the use of biological treatment processes for production water within the adjustment of the ammoniacal nitrogen concentration of such effluent to the levels acceptable by current legislation. Among the biological processes applied to the treatment of production water, the batch activated sludge system has stood out in Brazil, in treatment plants consisting of the following units: storage tank, flotation unit, equalization tank, sequential batch biological reactors, coagulation/flocculation unit, high-rate clarifier and sand filter. Currently, the production water that arrives at the production water treatment plants has an approximate salinity of 55 g·L−1 of NaCl, which can limit its treatment via biological processes. In this sense, there are some studies aiming at the removal of certain polluting compounds in high salinity, such as those described below. EP 2631219A1 describes a method for reducing total organic carbon in hypersaline water. US 2011010475A1 presents a treatment process for wastewater from oil fields (hypersaline wastewater) for degradation of hydrocarbons present in this type of effluent, through the addition of a consortium of isolated halophilic microorganisms. Both documents report ammoniacal nitrogen removal processes at salinity levels of up to 150 g/L, but always in synthetic effluents. In the present invention, the biological removal process of ammoniacal nitrogen from hypersaline effluents takes place through heterotrophic nitrifying/aerobic denitrifying microorganisms (HN/AD). When compared to the conventional ammonia removal process, which is based on the operational requirements for autotrophic nitrification, HN/AD processes present several advantages for effluent treatment plants. Ammoniacal nitrogen purification protocols with HN/AD microorganisms have the additional advantage of using an organic substrate. With this, it is possible to remove, in addition to ammonia, the contaminating organic matter from the effluent. Also, HN/AD microorganisms are tolerant to oxygen in both the nitrification and denitrification steps an