SUPPLEMENTAL CIRCULAR TO THE CIRCULARDATED 29 MAY 2024 IN RELATION TO(1) RE-APPOINTMENT OF INTERNATIONAL ANDDOMESTIC AUDITORS FOR 2024;(2) PROPOSED DOMESTIC ISSUANCE OF CORPORATE BONDS;AND(3) SUPPLEMENTAL NOTICE OF 2023 ANNUAL GENERAL MEETING

THIS SUPPLEMENTAL CIRCULAR IS IMPORTANT AND REQUIRES YOUR IMMEDIATE ATTENTION If you are in any doubt about this supplemental circular or as to the action to be taken you should consult a stockbroker or other registered dealer in securities bank manager solicitor professional accountant or other professional adviser.If you have sold or transferred all your shares in Datang Environment Industry Group Co. Ltd.* you should at once hand this supplemental circular together with the enclosed revised form of proxy to the purchaser(s) or transferee(s) or to the bank licensed securities dealer or other agent through whom the sale or transfer was effected for transmission to the purchaser(s) or transferee(s).Hong Kong Exchanges and Clearing Limited and The Stock Exchange of Hong Kong Limited take no responsibility for the contents of this supplemental circular make no representation as to its accuracy or completeness and expressly disclaim any liability whatsoever for any loss howsoever arising from or in reliance upon the whole or any part of the contents of this supplemental circular.Datang Environment Industry Group Co. Ltd.* (A joint stock company incorporated in the People’s Republic of China with limited liability) (Stock Code: 1272) SUPPLEMENTAL CIRCULAR TO THE CIRCULAR DATED 29 MAY 2024 IN RELATION TO (1) RE-APPOINTMENT OF INTERNATIONAL AND DOMESTIC AUDITORS FOR 2024; (2) PROPOSED DOMESTIC ISSUANCE OF CORPORATE BONDS; AND (3) SUPPLEMENTAL NOTICE OF 2023 ANNUAL GENERAL MEETING This supplemental circular should be read in conjunction with the circular of the Company dated 29 May 2024 (the “Original Circular”).The 2023 AGM Domestic Share Class Meeting and H Share Class Meeting will be held on Friday 28 June 2024 at No. 120 Zizhuyuan Road Haidian District Beijing the PRC. The 2023 AGM will be held at 3:30 p.m. on Friday 28 June 2024 at the same address the Domestic Share Class Meeting will be held at 4:00 p.m. at the same address (or immediately after the conclusion of or any adjourned meeting of the 2023 AGM) and the H Share Class Meeting will be held at 4:30 p.m. at the same address (or immediately after the conclusion of or any adjourned meeting of the Domestic Share Class Meeting) respectively as originally scheduled notices of which are set out in the Original Circular. A supplemental notice of the 2023 AGM (“Supplemental Notice”) notifying the 2023 AGM to be held as originally scheduled and containing additional proposed resolutions is set out on pages 9 to 11 of this supplemental circular.A revised form of proxy for the use at the 2023 AGM (the “Revised 2023 AGM Proxy Form”) containing the originally proposed resolutions and additional proposed resolutions in relation to (1) proposed re-appointment of international and domestic auditors for 2024; and (2) proposed domestic issuance of corporate bonds is enclosed herewith and are also published on the websites of the Stock Exchange (www.hkexnews.hk) and the Company (www.dteg.com.cn). Whether or not you intend to attend the 2023 AGM you are requested to complete and return the Revised 2023 AGM Proxy Form in accordance with the instructions printed thereon not less than 24 hours before the time fixed for holding the 2023 AGM or any adjournment thereof (as the case may be). Completion and return of the Revised 2023 AGM Proxy Form will not preclude you from attending the 2023 AGM and voting in person if you so wish and in such event the Revised 2023 AGM Proxy Form shall deemed to be revoked. 13 June 2024 * For identification purposes onlyCONTENTS Page DEFINITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 LETTER FROM THE BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 APPENDIX I – PROPOSED DOMESTIC ISSUANCE OF CORPORATE BONDS . . . . 7 SUPPLEMENTAL NOTICE OF 2023 ANNUAL GENERAL MEETING . . . . . . . . . . . . . . . 9 - i -DEFINITIONS In this supplemental circular unless the context otherwise requires the following expressions shall have the following meanings: “2023 AGM” the 2023 annual general meeting of the Company to be held at 3:30 p.m. on Friday 28 June 2024 at No. 120 Zizhuyuan Road Haidian District Beijing the PRC or any adjournment thereof (as the case may be) and the supplemental notice of which is set out on pages 9 to 11 of this supplemental circular “Articles of Association” the articles of association of the Company (as amended supplemented or otherwise modified from time to time) “Board” the board of Directors of the Company “China” or “PRC” the People’s Republic of China excluding for the purpose of this supplemental circular Hong Kong Macau Special Administrative Region and Taiwan “China Datang” China Datang Corporation Ltd. (中国大唐集团有限公司) a state- owned enterprise established on 9 April 2003 in accordance with the PRC laws and the controlling shareholder and a promoter of the Company “Company” Datang Environment Industry Group Co. Ltd.* (大唐环境产业集 团股份有限公司) a joint stock company incorporated in the PRC with limited liability the H Shares of which are listed on the Main Board of the Stock Exchange (stock code: 1272) “Class Meeting(s)” the Domestic Share Class Meeting and/or the H Share Class Meeting “controlling shareholder(s)” has the meaning ascribed under the Listing Rules “Director(s)” director(s) of the Company “Domestic Share(s)” the ordinary share(s) in the issued share capital of the Company with a nominal value of RMB1.00 each which are subscribed for and paid up in RMB by domestic investors and have not been listed on any stock exchanges “Group” the Company and its subsidiaries “H Share(s)” the overseas listed foreign share(s) of the Company with a nominal value of RMB1.00 each which are listed on the Main Board of the Stock Exchange - 1 -DEFINITIONS “Hong Kong” or “HK” Hong Kong Special Administrative Region of the PRC “Latest Practicable Date” 11 June 2024 being the latest practicable date prior to the printing of this supplemental circular for the purpose of ascertaining information contained therein “Listing Rules” the Rules Governing the Listing of Securities on the Stock Exchange “RMB” Renminbi the lawful currency of the PRC “Share(s)” Domestic Share(s) and/or H Share(s) “Shareholder(s)” holder(s) of Share(s) of the Company “Supervisor(s)” the supervisor(s) of the Company “Supervisory Committee” the supervisory committee of the Company “Stock Exchange” The Stock Exchange of Hong Kong Limited “subsidiary(ies)” has the meaning ascribed under the Listing Rules “%” per cent In this supplemental circular the English names of the PRC entities are translation of their Chinese names and are included herein for identification purposes only. In the event of any inconsistency the Chinese names shall prevail.- 2 -LETTER FROM THE BOARD Datang Environment Industry Group Co. Ltd.* (A joint stock company incorporated in the People’s Republic of China with limited liability) (Stock Code: 1272) Executive Director: Registered Office and Head Office in the PRC: Mr. Zhu Liming No. 120 Zizhuyuan Road Haidian District Non-executive Directors: Beijing Mr. Wang Junqi The PRC Mr. Shen Zhen Mr. Wu Daqing Principal Place of Business in Hong Kong: Mr. Chen Kan 31/F Tower Two Times Square Mr. Song Yunpeng 1 Matheson Street Causeway Bay Hong Kong Independent Non-executive Directors: Mr. Ye Xiang Mr. Mao Zhuanjian Mr. Gao Jiaxiang 13 June 2024 To the Shareholders Dear Sir/Madam SUPPLEMENTAL CIRCULAR TO THE CIRCULAR DATED 29 MAY 2024 IN RELATION TO (1) RE-APPOINTMENT OF INTERNATIONAL AND DOMESTIC AUDITORS FOR 2024; (2) PROPOSED DOMESTIC ISSUANCE OF CORPORATE BONDS; AND (3) SUPPLEMENTAL NOTICE OF 2023 ANNUAL GENERAL MEETING * For identification purposes only - 3 -LETTER FROM THE BOARD I. INTRODUCTIONReferences are made to the Original Circular and the notice of the 2023 AGM (the “OriginalNotice”) both dated 29 May 2024 which set out the time and venue of the 2023 AGM and contain the resolutions to be proposed at the 2023 AGM for Shareholders’ consideration and approval.This supplemental circular should be read in conjunction with the Original Circular. Unless otherwise defined capitalised terms used herein shall have the same meanings as those defined in the Original Circular.II. ADDITIONAL MATTERS TO BE RESOLVED AT THE 2023 AGM The purpose of this Supplemental Circular is to give you details of the following supplemental resolutions to be considered at the 2023 AGM and to give you a Supplemental Notice which is set out on pages 9 to 11 of this supplemental circular.Ordinary Resolution 1. Re-appointment of International and Domestic Auditors for 2024 An ordinary resolution will be proposed at the 2023 AGM to approve the re-appointment of Moore CPA Limited and Da Hua CPAs (Special General Partnership) as the international and domestic auditors of the Company for 2024 respectively with terms of engagement ended upon the conclusion of the 2024 annual general meeting of the Company and the grant of authority to the Board which further grants such authority to the senior management of the Company to determine their remunerations based on the actual auditing works performed by the auditors.Special Resolution 1. Proposed Domestic Issuance of Corporate Bonds A special resolution will be proposed at the 2023 AGM to consider and approve the application by the Company for the registration in respect of the issuance of corporate bonds in the total principal amount of RMB1 billion for a term of not more than ten years (inclusive) (the “Proposed Domestic Issuance of Corporate Bonds”) with the Shanghai Stock Exchange.Details of the Proposed Domestic Issuance of Corporate Bonds are set out in Appendix I to this supplemental circular.III. SUPPLEMENTAL NOTICE AND THE REVISED 2023 AGM PROXY FORM Since the Original Notice and the original proxy form (the “Original Proxy Form”) sent together with the Original Circular do not contain the new resolutions as set out in this supplemental circular the Supplemental Notice is set out on pages 9 to 11 of this supplemental circular. The Revised 2023 - 4 -LETTER FROM THE BOARD AGM Proxy Form is enclosed with this supplemental circular to include such new resolutions. The Revised 2023 AGM Proxy Form for the 2023 AGM are also published on the websites of the Stock Exchange (www.hkexnews.hk) and the Company (www.dteg.com.cn).Whether or not you are able to attend the 2023 AGM please complete and return the Revised 2023 AGM Proxy Form in accordance with the instructions printed thereon to the H Share Registrar or the Company’s Board office in the PRC as soon as possible and in any event not later than 24 hoursbefore the time appointed for holding the 2023 AGM or any adjournment thereof (the “ClosingTime”). Completion and return of the Revised 2023 AGM Proxy Form will not preclude the Shareholders from attending and voting at the 2023 AGM or any adjournment thereof (as the case may be) if they so wish. Pursuant to the Listing Rules voting by poll is required for any resolution put to vote at the 2023 AGM.A Shareholder who has not yet lodged the Original Proxy Form with the H Share Registrar is requested to lodge the Revised 2023 AGM Proxy Form if he/she wishes to appoint proxy(ies) to attend and vote at the 2023 AGM on his/her behalf. In this case the Original Proxy Form should not be lodged with the H Share Registrar.A Shareholder who has already lodged the Original Proxy Form with the H Share Registrar should take note of the following: (i) subject to (iii) below if no Revised 2023 AGM Proxy Form is lodged with the H Share Registrar the Original Proxy Form will be treated as a valid form of proxy lodged by him/her if correctly completed and signed. The proxy so appointed by the Shareholder shall be required to vote in such manner as he/she may be directed under the Original Proxy Form and in respect of the new resolutions as set out in the Supplemental Notice and the Revised 2023 AGM Proxy Form the proxy will be entitled to vote at his/her discretion or to abstain from voting on such resolutions; (ii) if the Revised 2023 AGM Proxy Form is lodged with the H Share Registrar before the Closing Time the Revised 2023 AGM Proxy Form if correctly completed and signed shall revoke and supersede the Original Proxy Form previously lodged by him/her. The Revised 2023 AGM Proxy Form will be treated as a valid form of proxy lodged by the Shareholder; and (iii) if the Revised 2023 AGM Proxy Form is lodged with the H Share Registrar after the Closing Time or if lodged before the Closing Time but is incorrectly completed the proxy appointment under the Revised 2023 AGM Proxy Form will be invalid. The proxy so appointed by the Shareholder under the Original Proxy Form if correctly completed will be entitled to vote in the manner as mentioned in (i) above as if no Revised 2023 AGM Proxy Form was lodged with the H Share Registrar.Accordingly the Shareholders are advised to complete the Revised 2023 AGM Proxy Form carefully and lodge the Revised 2023 AGM Proxy Form with (i) the H Share Registrar before the Closing Time (for holders of H Shares); or (ii) the Board office of the Company in the PRC (for holders of Domestic Shares) before the Closing Time.- 5 -LETTER FROM THE BOARD IV. VOTING BY POLL According to Rule 13.39(4) of the Listing Rules apart from certain exceptions any vote of Shareholders at a general meeting must be taken by poll.On a poll every Shareholder present in person or by proxy (or being a corporation by its duly authorised representative) shall have one vote for each Share registered in his/her/its name in the register of members. A Shareholder entitled to more than one vote need not use all his/her/its votes or cast all the votes he/she/it has in the same manner.V. RESPONSIBILITY STATEMENT This supplemental circular for which the Directors collectively and individually accept full responsibility includes particulars given in compliance with the Listing Rules for the purpose of giving information with regard to the Company. The Directors having made all reasonable enquiries confirm that to the best of their knowledge and belief the information contained in this supplemental circular is accurate and complete in all material respects and not misleading or deceptive and there are no other matters the omission of which would make any statement herein or this supplemental circular misleading.VI. RECOMMENDATION The Board considers that the (1) proposed re-appointment of international and domestic auditors for 2024; and (2) Proposed Domestic Issuance of Corporate Bonds are in the interests of the Company and the Shareholders as a whole and accordingly recommends the Shareholders to vote in favour of the relevant resolutions to be proposed at the 2023 AGM.Yours faithfully By order of the Board Datang Environment Industry Group Co. Ltd.* Zhu Liming Chairman * For identification purposes only - 6 -APPENDIX I PROPOSED DOMESTIC ISSUANCE OF CORPORATE BONDS To broaden financing channels and satisfy capital needs the Company proposes the public issuance of corporate bonds of RMB1 billion. The specific plan for the Proposed Issuance of Corporate Bonds is as follows: I. APPLICATION AND ISSUANCE PLAN: (1) Issue type: Corporate bonds (including general corporate bonds green corporate bonds technology innovation corporate bonds and other special types of corporate bonds excluding renewable corporate bonds); (2) Issue size: The total principal amount of this application for registration and issuance proposes to be RMB1 billion the Company could issued by tranche during the validity period of two years of the bond registration approval document of the Company the annual specific issuance limit shall be implemented in accordance with the annual financing plan approved by the Board; (3) Issue term: Not exceeding 10 years (inclusive); (4) Use of proceeds: Including but not limited to replenishment of working capital repayment of debts adjustment of debt structure and investment in projects; (5) Issue interest rate: Fixed interest rate determined based on the issue results through bookbuilding and payable annually without compounding; (6) Issue method: Public offering to professional investors in installments within the validity period of the approval documents; and (7) Place of listing and trading: Shanghai Stock Exchange. II. AUTHORISATION: In accordance with relevant PRC laws and regulations and the Articles of Association in order to complete the registration and issuance of corporate bonds in an efficient and orderly manner the Board proposes to the 2023 AGM to authorise the Board to delegate the authority to the chairman and his authorised person(s) to be responsible for the matters in relation to the registration and issuance of the corporate bonds and the authorisation matters include but not limited to: (1) To implement and execute the registration issuance and application for listing of corporate bonds including but not limited to formulating approving authorising signing executing amending and completing all necessary documents contracts agreements etc. in relation to the issuance and listing of corporate bonds and handling the application and issuance procedures for the issuance of corporate bonds; (2) Based on market conditions and the Company’s capital needs to determine the specific plan for the issuance of each tranche of corporate bonds including but not limited to the issue type issue size issue time issue term issue interest rate underwriting method credit enhancement - 7 -APPENDIX I PROPOSED DOMESTIC ISSUANCE OF CORPORATE BONDS mechanism use of proceeds whether to set special terms and the contents of relevant terms debt repayment guarantee arrangements and all other matters related to the issuance plan of each tranche of bonds; (3) To decide to engage an intermediary to assist the Company in handling the registration issuance and listing of the corporate bonds; to select a trustee manager for the registration and issuance of the corporate bonds and to formulate rules for bondholders’ meetings; (4) Except for matters that require reconsideration at the general meetings in accordance with relevant laws regulations and the Articles of Association if there are changes in regulatory policies or market conditions to adjust the issuance plan of corporate bonds and other related matters in accordance with the opinions of regulatory authorities or to decide on whether to continue the issuance of the corporate bonds based on actual situation; (5) To timely fulfill information disclosure obligations; (6) To handle the listing of the corporate bonds repayment of principal and interest and other matters upon completion of the issuance of the corporate bond; (7) To handle other matters related to the registration and issuance of the corporate bonds. The above authorisation shall be valid for 24 months from the date of consideration and approval at the 2023 AGM. If the Company obtains registration issuance approval permit or registration from regulatory authorities within the aforementioned period the validity period of the authorisation shall be automatically extended to the date of the completion of the abovementioned authorization matters.- 8 -SUPPLEMENTAL NOTICE OF 2023 ANNUAL GENERAL MEETING Hong Kong Exchanges and Clearing Limited and The Stock Exchange of Hong Kong Limited take no responsibility for the contents of this supplemental notice make no representation as to its accuracy or completeness and expressly disclaim any liability whatsoever for any loss howsoever arising from or in reliance upon the whole or any part of the contents of this supplemental notice.Datang Environment Industry Group Co. Ltd.* (A joint stock company incorporated in the People’s Republic of China with limited liability) (Stock Code: 1272) SUPPLEMENTAL NOTICE OF 2023 ANNUAL GENERAL MEETING Reference is made to the notice (the “Original Notice”) of the 2023 annual general meeting (the “2023AGM”) of Datang Environment Industry Group Co. Ltd.* (the “Company”) dated 29 May 2024. This supplemental notice (the “Supplemental Notice”) should be read together with the Original Notice.SUPPLEMENTAL NOTICE IS HEREBY GIVEN that the 2023 AGM will be convened at 3:30 p.m. on Friday 28 June 2024 at No. 120 Zizhuyuan Road Haidian District Beijing the PRC as scheduled. Terms used in this supplemental notice shall have the same meanings as those defined in the supplemental circular of the Company dated 13 June 2024 (the “Supplemental Circular”) unless otherwise specified.In addition to the resolutions set out in the Original Notice the following additional resolutions will be considered and if thought fit to be approved at the 2023 AGM: Ordinary Resolution (9) To consider and approve the re-appointment of Moore CPA Limited and Da Hua CPAs (Special General Partnership) as international and domestic auditors of the Company for 2024 respectively with terms of engagement ended upon the conclusion of the 2024 annual general meeting of the Company and the grant of authority to the Board which further grants such authority to the senior management of the Company to determine remunerations of the auditors.Special Resolution (11) To consider and approve the Proposed Domestic Issuance of Corporate Bonds. Note: The special resolution No. 9 as set out in the Original Notice shall be re-numbered as special resolution No. 10.* For identification purposes only - 9 -SUPPLEMENTAL NOTICE OF 2023 ANNUAL GENERAL MEETING For details of the above new resolutions please refer to the Supplemental Circular of the Company dated 13 June 2024.This Supplemental Notice should be read in conjunction with the Original Notice. Apart from the amendments set out above all the information contained in the Original Notice shall remain to have full force and effect.By order of the Board Datang Environment Industry Group Co. Ltd.* Zhu Liming Chairman Beijing the PRC 13 June 2024 Notes: (i) Save as the resolutions newly proposed there are no any other changes to the resolution set out in the Original Notice.For details of other resolutions and other related matters to be considered at the 2023 AGM please refer to the notice and circular of the 2023 AGM issued by the Company on 29 May 2024.(ii) As the proxy form published by the Company on the websites of the Stock Exchange (www.hkexnews.hk) and the Company (www.dteg.com.cn) on 29 May 2024 (the “Original Proxy Form”) does not contain the newly added resolutions set out in this supplemental notice a revised proxy form containing the above newly added resolutions (the “Revised 2023 AGM Proxy Form”) has been prepared and is enclosed in this Supplemental Notice.(iii) Important: If a Shareholder of the Company has not yet lodged the Original Proxy Form with the H Share Registrar or the Board office of the Company in the PRC such Shareholder is requested to lodge only the Revised 2023 AGM Proxy Form. A Shareholder who has lodged the Original Proxy Form with the H Share Registrar or the Board office of the Company in the PRC should note that: (1) the duly completed Revised 2023 AGM Proxy Form will be treated as the valid proxy form lodged by such Shareholder; (2) if such Shareholder fails to lodge the Revised 2023 AGM Proxy Form with the H Share Registrar or the Board office of the Company in the PRC the lodged Original Proxy Form if duly completed will remain effective and applicable to the extent permissible. For the additional resolutions not set out in the Original Proxy Form the proxy appointed under the Original Proxy Form shall have the right to vote at his/her discretion if no relevant instruction is received; and (3) any Revised 2023 AGM Proxy Form which is lodged with the H Share Registrar or the Board office of the Company in the PRC after the Deadline (as defined below) shall be invalid. The Original Proxy Form previously lodged by such Shareholder shall not be revoked. The Original Proxy Form if duly completed will be deemed effective and applicable to the extent permissible. For the additional resolutions not set out in the Original Proxy Form the proxy appointed under the Original Proxy Form shall have the right to vote at his/her discretion if no relevant instruction is received.(iv) Each Shareholder entitled to attend and vote at the 2023 AGM may by completing the Revised 2023 AGM Proxy Form appoint one or more proxies to attend and vote at the 2023 AGM on its behalf. A proxy need not be a Shareholder. With respect to any Shareholder who has appointed more than one proxy the proxy holders may only vote on a poll.- 10 -SUPPLEMENTAL NOTICE OF 2023 ANNUAL GENERAL MEETING (v) The Revised 2023 AGM Proxy Form shall be signed by the appointer or his attorney duly authorised in writing or in the case of a legal person must be either executed under its common seal or under the hand of its directors or attorney duly authorised.(vi) To be valid the Revised 2023 AGM Proxy Form must be lodged with the H Share Registrar Computershare Hong Kong Investor Services Limited at 17M Floor Hopewell Centre 183 Queen’s Road East Wanchai Hong Kong (for holders of H Shares) or the Company’s Board office in the PRC at No. 120 Zizhuyuan Road Haidian District Beijing the PRC 100097 (for holders of Domestic Shares) not less than 24 hours prior to the holding of the 2023 AGM or any adjourned meetings (the “Deadline”). If the Revised 2023 AGM Proxy Form is signed by another person under a power of attorney or other authorisation documents given by the appointer such power of attorney or other authorisation documents shall be notarised. The notarised power of attorney or other authorisation documents shall together with the Revised 2023 AGM Proxy Form be deposited at the specified place at the time set out in such form. Completion and return of the Revised 2023 AGM Proxy Form will not preclude Shareholders from attending and voting in person at the 2023 AGM or any adjourned meetings should you so wish. As at the date of this Supplemental Notice the executive Director is Mr. Zhu Liming; the non-executive Directors are Mr. Wang Junqi Mr. Shen Zhen Mr. Wu Daqing Mr. Chen Kan and Mr. Song Yunpeng; and the independent non-executive Directors are Mr. Ye Xiang Mr. Mao Zhuanjian and Mr. Gao Jiaxiang.This Supplemental Notice is available on the websites of the Stock Exchange (www.hkexnews.hk) and the Company (www.dteg.com.cn).