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<!--Date of creation: 03/29/2024-->
<!--Software architectural design and coding: A'c Dharmapremananda Avt.-->
<!--Copyright (c) 2024 I-NET Business Solutions, Inc. All Rights Reserved.-->
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  <import namespace="http://fasb.org/srt/2023" schemaLocation="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd" />
  <import namespace="http://fasb.org/us-gaap/2023" schemaLocation="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd" />
  <element id="scwo_NetLossPerShareBasicAndDiluted" name="NetLossPerShareBasicAndDiluted" nillable="true" xbrli:periodType="duration" type="num:perShareItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_WeightedAverageNumberOfSharesOutstandingBasicAndDiluted" name="WeightedAverageNumberOfSharesOutstandingBasicAndDiluted" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ConversionOfConvertiblePreferredSharesIntoCommonStockShares" name="ConversionOfConvertiblePreferredSharesIntoCommonStockShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ConversionOfConvertiblePreferredSharesIntoCommonStockAmount" name="ConversionOfConvertiblePreferredSharesIntoCommonStockAmount" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ExercisedOptionAndWarrantsAmount" name="ExercisedOptionAndWarrantsAmount" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ExerciseOfWarrantsShares" name="ExerciseOfWarrantsShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ExerciseOfWarrantsAmount" name="ExerciseOfWarrantsAmount" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_AmortizationOfAfsInvestmentSecuritiesUnrealizedLossInAociIntoInterestIncomeAsYieldAdjustment" name="AmortizationOfAfsInvestmentSecuritiesUnrealizedLossInAociIntoInterestIncomeAsYieldAdjustment" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_IncreaseDecreaseInUnearnedRevenue" name="IncreaseDecreaseInUnearnedRevenue" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ProceedsFromTheExerciseOfOptionsAndWarrants" name="ProceedsFromTheExerciseOfOptionsAndWarrants" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_EffectOfExchangeRatesOnCash" name="EffectOfExchangeRatesOnCash" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ChangeInUnrealizedLossOnAfsInvestmentSecurities" name="ChangeInUnrealizedLossOnAfsInvestmentSecurities" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_TransfersOfInvestmentSecuritiesFromAfsToHtm" name="TransfersOfInvestmentSecuritiesFromAfsToHtm" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_RecentAccountingPronouncementsNotYetAdoptedpolicypolicytextblock" name="RecentAccountingPronouncementsNotYetAdoptedpolicypolicytextblock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_AccruedContractLossProvisionAndOnerousContractspolicytextblock" name="AccruedContractLossProvisionAndOnerousContractspolicytextblock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_SummaryOfActivityRelatedToAccountsReceivableAllowanceForCreditLossesTableTextBlock" name="SummaryOfActivityRelatedToAccountsReceivableAllowanceForCreditLossesTableTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ScheduleOfRevenuesTableTextBlock" name="ScheduleOfRevenuesTableTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_SummaryOfUnearnedRevenueActivityTableTextBlock" name="SummaryOfUnearnedRevenueActivityTableTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_SummaryOfUnbilledAccountsReceivableActivityTableTextBlock" name="SummaryOfUnbilledAccountsReceivableActivityTableTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_UnrealizedLosses" name="UnrealizedLosses" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_InvestmentsAdjustedCost" name="InvestmentsAdjustedCost" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_AccountsAndReceivableAllowanceForCreditLoss" name="AccountsAndReceivableAllowanceForCreditLoss" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_AccountsReceivableAllowanceForCreditLossesCurrentPeriodProvision" name="AccountsReceivableAllowanceForCreditLossesCurrentPeriodProvision" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_RecoveryFromAccountsReceivable" name="RecoveryFromAccountsReceivable" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_AccountsAndFinancingReceivablesAllowanceForCreditLoss" name="AccountsAndFinancingReceivablesAllowanceForCreditLoss" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_RevenuesFromSaleOfTreatabilityServices" name="RevenuesFromSaleOfTreatabilityServices" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_RevenuesFromSales" name="RevenuesFromSales" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_AvailableForSaleSecuritiesFromInvestment" name="AvailableForSaleSecuritiesFromInvestment" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_EffectOfExchangeRateOnCashFromReclassification" name="EffectOfExchangeRateOnCashFromReclassification" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ShareBasedDescription" name="ShareBasedDescription" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_FiniteLivedIntangibleAssetUsefulLifeDuringPeriod" name="FiniteLivedIntangibleAssetUsefulLifeDuringPeriod" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_CommonSharesIssuedFairValue" name="CommonSharesIssuedFairValue" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_RevenuePercentage" name="RevenuePercentage" nillable="true" xbrli:periodType="duration" type="num:percentItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_PremiumsRevenuePercentage" name="PremiumsRevenuePercentage" nillable="true" xbrli:periodType="duration" type="num:percentItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_BillingsDeferredUnearnedRevenue" name="BillingsDeferredUnearnedRevenue" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ServicesPerformedButUnbilled" name="ServicesPerformedButUnbilled" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ServicesBilled" name="ServicesBilled" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_WeightedAverageExercisePriceExercisableAtDecember312023" name="WeightedAverageExercisePriceExercisableAtDecember312023" nillable="true" xbrli:periodType="instant" type="num:perShareItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2EndingBalance" name="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2EndingBalance" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_WeightedAverageExercisePriceExercised" name="WeightedAverageExercisePriceExercised" nillable="true" xbrli:periodType="duration" type="num:perShareItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_WeightedAverageRemainingContractualLifeYearsBeginningBalance" name="WeightedAverageRemainingContractualLifeYearsBeginningBalance" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_WeightedAverageRemainingContractualLifeYearsEndingBalance" name="WeightedAverageRemainingContractualLifeYearsEndingBalance" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsWarrantsExercised" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsWarrantsExercised" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_IssuanceOfCommonStock" name="IssuanceOfCommonStock" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_UnrecognizedCompensationVestingPeriod" name="UnrecognizedCompensationVestingPeriod" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_LiabilityForPreferredStockShares" name="LiabilityForPreferredStockShares" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_StockOptionsReservedShares" name="StockOptionsReservedShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ReservedOptionsRemainingShares" name="ReservedOptionsRemainingShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_IssuanceOfCommonShares" name="IssuanceOfCommonShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ExerciseOfCommonStock" name="ExerciseOfCommonStock" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ExercisePrice" name="ExercisePrice" nillable="true" xbrli:periodType="instant" type="num:perShareItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParties" name="RelatedPartyTransactionExpensesFromTransactionsWithRelatedParties" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_RelatedPartyCost" name="RelatedPartyCost" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_StockInExcessPercentageOfOutstandingShare" name="StockInExcessPercentageOfOutstandingShare" nillable="true" xbrli:periodType="duration" type="num:percentItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_LegalSettlementIssuableShares" name="LegalSettlementIssuableShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_AccruedLegalSettlementCurrent" name="AccruedLegalSettlementCurrent" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ShareBasedGoodsAndNonemployeeServicesTransactionValuationMethodRiskFreeInterestRates" name="ShareBasedGoodsAndNonemployeeServicesTransactionValuationMethodRiskFreeInterestRates" nillable="true" xbrli:periodType="duration" type="num:percentItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRates" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRates" nillable="true" xbrli:periodType="duration" type="num:percentItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_DeferredTaxAssetsStartupCost" name="DeferredTaxAssetsStartupCost" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_DeferredTaxAssetsOtherIntangibleAssets" name="DeferredTaxAssetsOtherIntangibleAssets" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_DeferredTaxAssetsOtherIntangibleAssetsOtherAccruals" name="DeferredTaxAssetsOtherIntangibleAssetsOtherAccruals" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_DeferredTaxAssetsUnearnedRevenue" name="DeferredTaxAssetsUnearnedRevenue" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_DeferredTaxAssetsReservesAndAllowances" name="DeferredTaxAssetsReservesAndAllowances" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_IncomeTaxReconciliationPermanentDifferences" name="IncomeTaxReconciliationPermanentDifferences" nillable="true" xbrli:periodType="duration" type="num:percentItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_IncomeTaxReconciliationOther" name="IncomeTaxReconciliationOther" nillable="true" xbrli:periodType="duration" type="num:percentItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_LiquidityCapitalResourcesAbstract" name="LiquidityCapitalResourcesAbstract" nillable="true" abstract="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
  <element id="scwo_RevenueAbstract" name="RevenueAbstract" nillable="true" abstract="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
  <element name="USTreasurySecuritiessMember" id="scwo_USTreasurySecuritiessMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="WarrantsMember" id="scwo_WarrantsMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="OneCustomerMember" id="scwo_OneCustomerMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="RevenueMember" id="scwo_RevenueMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="OptionsMember" id="scwo_OptionsMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="LicenseAgreementMember" id="scwo_LicenseAgreementMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="DukeUniversityMember" id="scwo_DukeUniversityMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="EquipmentRevenuesMember" id="scwo_EquipmentRevenuesMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="ServiceRevenueMember" id="scwo_ServiceRevenueMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="ThreeSevenFourWaterMember" id="scwo_ThreeSevenFourWaterMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="ConsultantMember" id="scwo_ConsultantMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="BlankCheckMember" id="scwo_BlankCheckMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="TwoZeroTwoOneEquityIncentivePlanMember" id="scwo_TwoZeroTwoOneEquityIncentivePlanMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="EquityDistributionAgreementMember" id="scwo_EquityDistributionAgreementMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
  <element name="TwentyTwentyOnePlanMember" id="scwo_TwentyTwentyOnePlanMember" nillable="true" xbrli:periodType="duration" type="nonnum:domainItemType" substitutionGroup="xbrli:item" />
</schema>
