39. Define environmental engineering and its goals. (3 marks) 40. What are the different types of water treatment processes? (3 marks) 41. Explain the concept of wastewater treatment. (3 marks) 42. What is the significance of solid waste management? (3 marks) 43. Describe the process of air pollution control. (3 marks) 44. What are the principles of sustainable development in civil engineering? (3 marks) 45. Explain the impact of construction activities on the environment. (3 marks)