Many countries have improved their sanitation with improved standards of waste disposal.
第一个improved前有with ,还能看作完成时吗?还是被动的随着或者形容词?
have improved：目前完成时，谓语。主动意义。
improved standards of waste disposal. 过去分词作定语，被动意义，修饰standards。没必要区别improved是形容词还是过去分词，就按过去分词对待。