There are several study materials and resources available for environmental engineering concepts in the civil engineering optional subject. These resources can help students gain a deeper understanding of the subject and prepare effectively for exams. Below are some key study materials and resources:

1. Textbooks:
- "Environmental Engineering: Water, Wastewater, Soil and Groundwater Treatment and Remediation" by Nelson L. Nemerow and Franklin J. Agardy.
- "Introduction to Environmental Engineering and Science" by Gilbert M. Masters and Wendell P. Ela.

2. Reference Books:
- "Principles of Environmental Engineering and Science" by Mackenzie L. Davis and Susan J. Masten.
- "Environmental Engineering: Fundamentals, Sustainability, Design" by James R. Mihelcic and Julie B. Zimmerman.

3. Lecture Notes and Handouts:
- Universities and educational websites often provide lecture notes and handouts on environmental engineering concepts. These materials can be downloaded and used for self-study.

4. Online Courses and Video Lectures:
- Platforms like Coursera, edX, and NPTEL offer online courses on environmental engineering. These courses provide video lectures, quizzes, and assignments to enhance learning.

5. Previous Year Question Papers:
- Solving previous year question papers is crucial for exam preparation. These papers help students understand the exam pattern and the types of questions asked.

6. Mock Tests and Practice Papers:
- EduRev provides mock tests and practice papers specifically designed for civil engineering optional subjects. These tests simulate the exam environment and help students assess their preparation level.

7. Online Forums and Discussion Groups:
- Joining online forums and discussion groups related to civil engineering can be helpful. Students can interact with peers, ask questions, and gain insights from experienced professionals.

8. Study Guides and Tutorials:
- Various study guides and tutorials are available online, which summarize the key concepts and provide step-by-step explanations.

In conclusion, there are numerous study materials and resources available for environmental engineering concepts in the civil engineering optional subject. Students can utilize textbooks, reference books, lecture notes, online courses, video lectures, previous year question papers, mock tests, online forums, study guides, and tutorials to enhance their understanding and prepare effectively for exams.