假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌的以下作文。文中共有10处语言错误，每句中最多有两处，每处错误仅涉及一个单词的增加，删除或修改。
增加： 在缺词处加一个漏字符号（^）,并在其下面写出该加的词。
删除：把多余的词用斜线（\）划掉。
修改： 在错的词下划一横线，并在该词下面写出修改后的词。
The world is not only hungry, but also thirst． This may sounds strange, since nearly seventy percent of the earth's surface is covered with water． But about ninety percent of this is sea water． Man and most of the animals can only drink and use the remained ten percent of water --- fresh water． The need for water is increased day by day． Only when steps are taken to deal with this problem immediate can we avoid a severe worldwide water shortage later on． One of the first steps are to develop ways to reuse them． Experiments have already carried out in this field． The used water has been pumped to a water purifying plant that it can be separated from waste matters and treated with chemicals so that it can be reused again．