Farooq, Robina. creator text S.l.] LAP Lambert Academic Publishing 2009 monographic 124 p. ; Sewage--Purification Water--Purification 3838327675 (paperback) 9783838327679 (paperback) http://www.amazon.com/exec/obidos/ASIN/3838327675/chopaconline-20 http://www.amazon.com/exec/obidos/ASIN/3838327675/chopaconline-20