Recycled water systems

The phosphate fertilizer industry is defined as eight separate processes phosphate rock grinding, wet process phosphoric acid, phosphoric acid concentration, phosphoric acid clarification, normal superphosphate, triple superphosphate, ammonium phosphate, and sulfuric acid. Practically all phosphate manufacturers combine the various effluents into a large recycle water system. It is only when the quantity of recycle water increases beyond the capacity to contain it that effluent treatment is necessary. 

Singh S, Henderson RK, Baker A, Stuetz RM, Khem SJ (2012) Cheuacterisadon of reverse osmosis permeates from munidpal recycled water systems using fluorescence spectroscopy implications for integrity monitoring. J Membr Sci 421 22 180-189... 

Modem practice is to maintain the white water system as closed as possible, ie, as much water as is compatible with efficient machine operation is recycled. The loss of fibers and inert furnish components, particularly clay, has been gready reduced. Eiber losses, however, stiU occur into the white water, and greater economy of operation may be achieved if these fibers could be recovered. Thus, it is common to design a fiber-recovery system into the white water cycle. The three general types of save-all fiber recovery are based on filtration (qv), dotation (qv), and sedimentation (qv). If these are operated efficiendy, the net fiber loss can be less than 1%. 

It is also important to study the interactions of papermaking additives (4) in the paper machine water system some additives act synergisticaHy, so that the performance of each is enhanced by the presence of the other. However, some additives have a negative impact on the performance of other additives, or on other desirable paper properties. Thus, optimization of the addition points and usage rates of the entire additive system is necessary in order to maximize performance of the chemical additives and the paper sheet properties, and to minimize cost and negative interactions both on the paper machine and in the white-water system. This is especially tme as unanticipated additives enter the wet end of the paper machine from recycled furnishes, including coated broke (5). 

From Allyl Alcohol. The reaction of allyl alcohol [107-18-6] with chlorine and water gives a mixture of glycerol m on ochl orohydrin s consisting of 73% 3-chloropropane-l,2-diol and 27% of 2-chloropropane-l,3-diol (57). In a recycle reaction system in which allyl alcohol is fed as a 4.5—5.5 wt % solution, chlorine is added at a rate of 7—9 moles per hour. The reaction time is about five seconds, the reaction temperature 50—60°C and the recycle ratio is 10—20 1. Under these conditions m on ochl orohydrin s have been obtained in 88% yield with 9% dichlorohydrins (58) (see Allyl ALCOHOL AND DERIVATIVES). 

AU industrial operations produce some wastewaters which must be returned to the environment. Wastewaters can be classified as (1) domestic wastewaters, (2) process wastewaters, and (3) coohng waste-waters. Domestic wastewaters are produced by plant workers, shower facihties, and cafeterias. Process wastewaters result from spills, leaks, and product washing. Coohng wastewaters are the result of various cooling processes and can be once-pass systems or multiple-recycle cooling systems. Once-pass coohng systems employ large volumes... 

Recycle/reuse involves the use of pollutant-laden streams within the process. Typically, separation technologies are key elements in a recycle/reuse system to recover valuable materials such as solvents, metals, inorganic species, and water. 

Figure 8-3 Three basic types of cooling water systems. Top the once-through system where the cooling water is used once and then discharged. Middle the open recirculation system where the water is cooled and recycled through a system in which it comes in direct contact with air. Bottom a closed recirculation system where the water is cooled and recycled without coming in direct contact with the atmosphere.

In the past twenty years many legal provisions have been created to regulate substance flows (recycling management systems, waste management, electrical and automotive recycling). In many instances these laws exphcitly contain threshold values for certain substances or even ban certain substances. They are thus very effective on the use of these substances in production processes. This is also tme for threshold values of chlorinated compounds in industrial waste, the ban on certain heavy metals in the automotive industry and substance-related requirements for waste water from the textile industry (Annexe 38 of Waste Water Ordinance ). 

The process at Three Mile Island involved nuclear fission and subsequent reactor cooling using circulating water. The primary water was kept under pressure to prevent boiling. Heat was transferred to a secondary water system that supplied power to a steam generator. Upon completion of this step, steam condensate was recovered and recycled. All radioactive materials, including primary water, were enclosed in a lined concrete containment building to prevent their escape to the atmosphere. 

Mixed fertilizer (subcategory G) treatment technology consists of a closed-loop contaminated water system, which includes a retention pond to settle suspended solids. The water is then recycled back to the system. There are no liquid waste streams associated with the blend fertilizer (subcategory G) process, except when liquid air scrubbers are used to prevent air pollution. Dry removals of air pollutants prevent a wastewater stream from being formed. 

Air streams from the digestion system, vacuum cooler, concentrator, and other areas where fluorine is evolved are connected to a highly efficient absorption system, providing extremely high volumes of water relative to the stream. The effluent from this absorption system forms part of the recycled water and is eventually discharged as part of the product used for fertilizer manufacture. The Minnesota plant requires a constant recirculating water load in excess of 3000 gpm (11.4 m /min), but multiple use and recycle reduce makeup requirements to less than 400 gpm (1.5 m /min) or a mere 13% of total water use. 

Kenawy 64) immobilized ammonium and phosphonium peripheral functionalized dendritic branches on a montmorillonite supported chloromethylstyrene/methyl methacrylate copolymer (74-75). These polymer/montmorillonite-supported dendrimers were used as phase transfer catalysts (PTC) for the nucleophilic substitution reaction between -butyl bromide and thiocyanate, cyanide, and nitrite anions in a toluene or a benzene/water system. These PT catalysts could be recycled by filtration of the functionalized montmorillonite from the reaction mixture. Generally,... 

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