These oooplanltton masses are seliaonuolled by eating out their algal ioods, and can in their tut-n be eaten by rash in Subsequem pond systems. 01 the pH, which varies troth Inngstum and in 214mm eyeles, it too increases irom stage to Stage: anaerobic pH is 2 .s, taeiilatrve pti 7 5~B 2, and aerobic pH 754.5 in clogged algal waters at night, it nray climb higher At the amblc stage, the BOD ' only 357 mg/l, due mainly to nitrogenous compounds, the suspended solids 12-50 mg/l inow mainly algae and woplank- tonl. About 30% pi these have been removed and incorporated into lite iorms, and the metal levels are now down to World Health Organisation standards, The water can be used tor irrigation, or iiltered via rush beds tosiieants Seasonal changes are noticeable, in winter, more hydrogen sulphide is given oii by anaerobic ponds ts-ls mg/l compared with summer-s H rag/ll, and wtnds rrtay rontribute more to oxygen levels in open ponds than do algae, tn winter too, more ammonia tell-id is released to the atmosphere. Summer sees residues oxidised to nitrates The oxygen being provided more try algae than by wind, less hydrogen sulphide is given oil, and there are greater ranges at temperature in winter (lo—IS'CD, decornposrtton slows and sludge levels build up, only to be more actively converted in the summer warmth oi ILZZT (“JPN BO D is 495 ltg/ha/day in winter, mat lrg/tia/day in summer tat optimum pond eonditionst, showing that activity almost doubles as temperature increases Consequently, almost twrre as much gas as methane is given oii in summer tor in irrrrrrd drgesterst in winter. the cooling water ot methane—powered engines can provide the essc ' heat to drgesters via a closed loop pipe in all, this simpte lagoon series produees a very beneticral eiiluent irom heavxlyspullmed iniluent However. there are even more sophisticated biologrral treatments is Hedithuse eiteeted lay the higher plants As on tried below, some genera ot rushes, sedges, and iloaiing plants ran greatly assist with removal oi heavy metals and human pathogens. but perhaps more imponantly, some plans can also brealt dawn halogenated tehlorrne, bronunel hydrocarbons synthesised as herbicides and pesticides lsrael (Ntw Scientist, 12 Feb 7‘?) leads sewage waters to long eanalised ponds, aglmed try slnwlysrlvulving paddleswheel aerators ponds are 0.5 in or less deep Under bright sunlight ior under glasshouse eoverst dense algal mats ior-rn. and these are broken up by the addition oi alunuiuum sulphate ta pollutanllt, slrimmed our drained, tentrihrged. steam—dried, and ted ma'mu carp or ehieltens ialthough l imagine that arp could sellst'eed on aguatre algaet Algal protein replaces soil oi soya bean protein in teed rations to poultry Total treatment by these methods takes about 4 days The water is alkaline and somewhat anaerobie, needing more agitation in winter or on :00! days. Holland runs sewage to srrrular canals, and reaps reeds m plants as green erop or tor erait supplies. it has been iound (Ems u. winter '85! that the arriiicial aeration oi iamrlative ponds is most eiiietent ll run at intervals at two hours in s lanai, oi the nmet The taeulattve bacteria lollow Iwo digestive modes. and operate best ii a rush oi r is supplied aiter a itmr-hour anaerobic period, excilelillg earbon dioxide and thus reducing the bullt oi sludge There are corresponding reductions in energy costs ior aeration. Nitrogen was reduced iroin 20 mg/l to less than 5 mg/l, phosphorus irom s 5 mg/l to less than i mg/l when terrie chloride was supplied, The process has been dubbed A.A.A iattemairng aerobic and anaerobiet digestion nius, agitation oi anaerobic systems by bubbling with «impressed methane, and A A A oi iaeulatrve ponds can be used to obtain useiul yields oi methane and hishrpmleln alage irom sewage As tor the aerobic ponds, such higher plants as water hyaeirtth removed res dual metals, surplus nutrients, and ttecsir group oi b i (Nero Selentrsr, 4 0d ‘79, p 29t Microwave radiation can also be eiiective at breaking up algal mats, and sterilising algal pmducls, eliminating toxre alumimum salta As ior temperatures, solar ponds used in eonntrwtron with compact anaerobic ponds can supply the low grade heat necessary tor eiitoent sludge digestion. and methane will drive any motors needed ior both aera. oon and the gas compression used tor the agitation oi sludge, The whole processing system can be made very cumpacl, and at the aerolare pond level, throughitow ean lae led to tirewaod or tuel iorost systems, to irrigated grasslands tas at Werribeel, or via trieltls irngatron in mops in and areas. rioal treatment, now in use in Holland and recommended by scientists at the Mar Planelt lnstthite in Switrerland, can be released via a sinuous, sealed eanal ot a variety oi mshes and iloaiing water plants, Waters polluted with metals, bioodes, or sewage can be cleaned by travelling through raed beds oi Strrpvs, Typira. arid lunevs, or by harvesting oii iloaiing plants such as water hyaernth The nrsties and sedges can be mown and removed periodioally tor mukh oreellitlose Fm untreated sewage, a holding time ni “Lu days is neeessary, or travel through a serrcs oi mzzplike gravel rlter tanalr with iloaiing weeds and sedges ror swimmrng pools and less polluted systems, a pumped 'sytle- oi water through terns, rushes, and watereress suiiices to remove urine and leaves Such pools need a 23.30 em (9-!2 rneht eoarse river gravel base, with intalte pipes below, and a skimming notch ior leaves apestes recommended are - phrrgrnrtes eorrrnrvrrrs and spp., Typhr spp- Florculate colloids, dry out sludges, eliminate pathogens - SChaawptnilu spp, Takes up copper. cobalt, mrlret manganese, exudes mould antibiotics. - 5rrrpvs sppi breaks down phenols, ineludmg toaie pentaehloiophenol Low to zero populations oi : soil, eohiorm barmt-ia, Salmonella, and criteroeorei are lound atter water is 177