The  NPDES  permit  requires  that  certain  tests be  made  on  the  effluent  on  a  regular  schedule. Effluent  testing  may  include,  but  is  not  limited to,  flow  measurement,  temperature,  BOD  or COD, suspended solids, pH, DO, coliform count, and  chlorine  residual.  Test  results  must  be reported to the regulating agency. Along with the required tests, operators should check the receiv- ing water, especially on small streams and lakes. Laboratory  tests  and  visual  checks  may  show  that a problem exists in the receiving water and that something   needs   to   be   done.   Plant   operators cannot usually test large rivers, bays, lakes, and gulfs. If an effluent containing a toxic substance is accidentally discharged to a receiving water that is used downstream as a drinking water supply, for  recreation,  or  for  livestock  watering,  operators must  call  the  regulating  agency  and  the downstream  water  users  at  once.  Regulating  agen- cies can then help curb the problem, and drink- ing  water  suppliers  will  have  enough  time  to  close their  water  intake  lines  until  the  problem  is stopped. This will also warn people in recreation areas and give farmers and ranchers time to move livestock  to  a  safe  water  supply. Discharge for Recycling In  some  areas  where  there  is  a  shortage  of water, wastewater effluent is recycled for industry, recreation, irrigation, and fire control use. Many industries can use treated wastewater for cooling and cleaning. Often this is cheaper for the industry than  using  potable  (drinking)  water.  Lakes  for fishing  and  boating  have  been  maintained  with recycled  wastewater.  Records  show  that  these man-made lakes are often no more hazardous to the  users  than  natural  lakes.  Recycled  wastewater is  seldom  used  as  a  drinking  water  supply. Monitoring  of  effluent  discharged  for  recycl- ing is very important. Only by monitoring can the operator be sure that the effluent is good enough to be used. Recycling units may include extended settling  and  biological  stabilization  in  holding ponds,  sand  filtering,  and  disinfection.  Quality control  is  a  must  since  the  recycled  water  must be  safe. Discharge for Land Application (Irrigation) Irrigation  with  wastewater  effluent  is  fre- quently used in some areas. Before irrigating, it is  necessary  to  consider  the  contour  of  the  area for irrigation, soil type, ground water table, and potential  damage  to  water  supplies.  The  joint EPA/Army  manual,  EPA  625/1-77-008   Process Design Manual for Land Treatment of Municipal Wastewater,   provides  further  guidance  on  this subject. Hillsides  and  other  areas  with  steep  slopes  are not  often  used  for  irrigation.  Too  much  runoff may  occur.  Irrigation  equipment  is  harder  to move, control, and maintain. Each area to be used for  irrigation  should  be  surveyed  by  a  qualified person.   Often,   areas   with   slopes   on   which normal  farm  machinery  can  be  used  can  be irrigated by a sprinkler system or by a jet or spray gun.  Terracing  and  contour  furrowing  help  pre- vent   runoff.   Flooding,   overland   flow,   and furrow irrigation may require special work done to  the  land.  This  may  include  leveling,  grading, ditches,  and  dikes. Soil type and structure affect the rate at which the  wastewater  can  be  applied  and  absorbed. Average loams and sandy loams absorb and filter well. Clay and other types of tight soil are not as good.  Deep  plowing  and  chiseling  make  these  soils better  for  wastewater  irrigation.  Very  sandy  or gravelly  soils  have  very  high  percolation  or absorbing qualities. But when these soils are in contact  with  the  ground  water  table,  pollutants may get into underground water supplies before they can be filtered out. Tight, sandy, and gravelly soils can be improved for absorbing and filtering by  plowing  crops  under. Row crops may be watered by furrow, spray, and/or  sprinkler  irrigation.  Spray  irrigation  is used where gravity flow is not practical in all parts of an effluent disposal plot or field. There should be  gravity  flow  from  one  end  of  the  row  to  the other.  A  lot  of  grading  is  needed  to  prepare  a  field for furrow irrigation. Long rows without enough slope will result in boggy parts of the field while other  parts  will  not  get  enough  water.  Furrow irrigation on steep slopes may cause too much ero- sion.  Operators  in  charge  of  this  type  of  irriga- tion need special skill and experience to make sure a  fairly  even  amount  of  water  reaches  all  parts of  the  field. Grass  crops  are  often  easy  to  irrigate.  The grasslands may be pastures, meadows, parks, turf, or sodded areas of airfields and golf courses. The amount  of  water  applied  and  how  often  it  is applied  are  not  as  important  as  for  row  crops. Effluent can be applied to grassland by overland flow, sprinkler heads, or by jet or spray guns. The stems,  leaves,  and  roots  of  the  grasses  make  a good  filter  and  help  prevent  rapid  runoff.  Grasses 10-28